From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sun, 2 Oct 2022 21:28:53 -0700
Subject: [PATCH] Threaded Regions

See https://docs.papermc.io/folia/reference/overview and
https://docs.papermc.io/folia/reference/region-logic

diff --git a/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRInt2IntHashTable.java b/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRInt2IntHashTable.java
new file mode 100644
index 0000000000000000000000000000000000000000..7869cc177c95e26dd9e1d3db5b50e996956edb24
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRInt2IntHashTable.java
@@ -0,0 +1,664 @@
+package ca.spottedleaf.concurrentutil.map;
+
+import ca.spottedleaf.concurrentutil.util.ArrayUtil;
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import ca.spottedleaf.concurrentutil.util.Validate;
+import io.papermc.paper.util.IntegerUtil;
+import java.lang.invoke.VarHandle;
+import java.util.Arrays;
+import java.util.function.Consumer;
+import java.util.function.IntConsumer;
+
+public class SWMRInt2IntHashTable {
+
+    protected int size;
+
+    protected TableEntry[] table;
+
+    protected final float loadFactor;
+
+    protected static final VarHandle SIZE_HANDLE = ConcurrentUtil.getVarHandle(SWMRInt2IntHashTable.class, "size", int.class);
+    protected static final VarHandle TABLE_HANDLE = ConcurrentUtil.getVarHandle(SWMRInt2IntHashTable.class, "table", TableEntry[].class);
+
+    /* size */
+
+    protected final int getSizePlain() {
+        return (int)SIZE_HANDLE.get(this);
+    }
+
+    protected final int getSizeOpaque() {
+        return (int)SIZE_HANDLE.getOpaque(this);
+    }
+
+    protected final int getSizeAcquire() {
+        return (int)SIZE_HANDLE.getAcquire(this);
+    }
+
+    protected final void setSizePlain(final int value) {
+        SIZE_HANDLE.set(this, value);
+    }
+
+    protected final void setSizeOpaque(final int value) {
+        SIZE_HANDLE.setOpaque(this, value);
+    }
+
+    protected final void setSizeRelease(final int value) {
+        SIZE_HANDLE.setRelease(this, value);
+    }
+
+    /* table */
+
+    protected final TableEntry[] getTablePlain() {
+        //noinspection unchecked
+        return (TableEntry[])TABLE_HANDLE.get(this);
+    }
+
+    protected final TableEntry[] getTableAcquire() {
+        //noinspection unchecked
+        return (TableEntry[])TABLE_HANDLE.getAcquire(this);
+    }
+
+    protected final void setTablePlain(final TableEntry[] table) {
+        TABLE_HANDLE.set(this, table);
+    }
+
+    protected final void setTableRelease(final TableEntry[] table) {
+        TABLE_HANDLE.setRelease(this, table);
+    }
+
+    protected static final int DEFAULT_CAPACITY = 16;
+    protected static final float DEFAULT_LOAD_FACTOR = 0.75f;
+    protected static final int MAXIMUM_CAPACITY = Integer.MIN_VALUE >>> 1;
+
+    /**
+     * Constructs this map with a capacity of {@code 16} and load factor of {@code 0.75f}.
+     */
+    public SWMRInt2IntHashTable() {
+        this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR);
+    }
+
+    /**
+     * Constructs this map with the specified capacity and load factor of {@code 0.75f}.
+     * @param capacity specified initial capacity, > 0
+     */
+    public SWMRInt2IntHashTable(final int capacity) {
+        this(capacity, DEFAULT_LOAD_FACTOR);
+    }
+
+    /**
+     * Constructs this map with the specified capacity and load factor.
+     * @param capacity specified capacity, > 0
+     * @param loadFactor specified load factor, > 0 && finite
+     */
+    public SWMRInt2IntHashTable(final int capacity, final float loadFactor) {
+        final int tableSize = getCapacityFor(capacity);
+
+        if (loadFactor <= 0.0 || !Float.isFinite(loadFactor)) {
+            throw new IllegalArgumentException("Invalid load factor: " + loadFactor);
+        }
+
+        //noinspection unchecked
+        final TableEntry[] table = new TableEntry[tableSize];
+        this.setTablePlain(table);
+
+        if (tableSize == MAXIMUM_CAPACITY) {
+            this.threshold = -1;
+        } else {
+            this.threshold = getTargetCapacity(tableSize, loadFactor);
+        }
+
+        this.loadFactor = loadFactor;
+    }
+
+    /**
+     * Constructs this map with a capacity of {@code 16} or the specified map's size, whichever is larger, and
+     * with a load factor of {@code 0.75f}.
+     * All of the specified map's entries are copied into this map.
+     * @param other The specified map.
+     */
+    public SWMRInt2IntHashTable(final SWMRInt2IntHashTable other) {
+        this(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, other);
+    }
+
+    /**
+     * Constructs this map with a minimum capacity of the specified capacity or the specified map's size, whichever is larger, and
+     * with a load factor of {@code 0.75f}.
+     * All of the specified map's entries are copied into this map.
+     * @param capacity specified capacity, > 0
+     * @param other The specified map.
+     */
+    public SWMRInt2IntHashTable(final int capacity, final SWMRInt2IntHashTable other) {
+        this(capacity, DEFAULT_LOAD_FACTOR, other);
+    }
+
+    /**
+     * Constructs this map with a min capacity of the specified capacity or the specified map's size, whichever is larger, and
+     * with the specified load factor.
+     * All of the specified map's entries are copied into this map.
+     * @param capacity specified capacity, > 0
+     * @param loadFactor specified load factor, > 0 && finite
+     * @param other The specified map.
+     */
+    public SWMRInt2IntHashTable(final int capacity, final float loadFactor, final SWMRInt2IntHashTable other) {
+        this(Math.max(Validate.notNull(other, "Null map").size(), capacity), loadFactor);
+        this.putAll(other);
+    }
+
+    public final float getLoadFactor() {
+        return this.loadFactor;
+    }
+
+    protected static int getCapacityFor(final int capacity) {
+        if (capacity <= 0) {
+            throw new IllegalArgumentException("Invalid capacity: " + capacity);
+        }
+        if (capacity >= MAXIMUM_CAPACITY) {
+            return MAXIMUM_CAPACITY;
+        }
+        return IntegerUtil.roundCeilLog2(capacity);
+    }
+
+    /** Callers must still use acquire when reading the value of the entry. */
+    protected final TableEntry getEntryForOpaque(final int key) {
+        final int hash = SWMRInt2IntHashTable.getHash(key);
+        final TableEntry[] table = this.getTableAcquire();
+
+        for (TableEntry curr = ArrayUtil.getOpaque(table, hash & (table.length - 1)); curr != null; curr = curr.getNextOpaque()) {
+            if (key == curr.key) {
+                return curr;
+            }
+        }
+
+        return null;
+    }
+
+    protected final TableEntry getEntryForPlain(final int key) {
+        final int hash = SWMRInt2IntHashTable.getHash(key);
+        final TableEntry[] table = this.getTablePlain();
+
+        for (TableEntry curr = table[hash & (table.length - 1)]; curr != null; curr = curr.getNextPlain()) {
+            if (key == curr.key) {
+                return curr;
+            }
+        }
+
+        return null;
+    }
+
+    /* MT-Safe */
+
+    /** must be deterministic given a key */
+    protected static int getHash(final int key) {
+        return it.unimi.dsi.fastutil.HashCommon.mix(key);
+    }
+
+    // rets -1 if capacity*loadFactor is too large
+    protected static int getTargetCapacity(final int capacity, final float loadFactor) {
+        final double ret = (double)capacity * (double)loadFactor;
+        if (Double.isInfinite(ret) || ret >= ((double)Integer.MAX_VALUE)) {
+            return -1;
+        }
+
+        return (int)ret;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public boolean equals(final Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        /* Make no attempt to deal with concurrent modifications */
+        if (!(obj instanceof SWMRInt2IntHashTable)) {
+            return false;
+        }
+        final SWMRInt2IntHashTable other = (SWMRInt2IntHashTable)obj;
+
+        if (this.size() != other.size()) {
+            return false;
+        }
+
+        final TableEntry[] table = this.getTableAcquire();
+
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry curr = ArrayUtil.getOpaque(table, i); curr != null; curr = curr.getNextOpaque()) {
+                final int value = curr.getValueAcquire();
+
+                final int otherValue = other.get(curr.key);
+                if (value != otherValue) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public int hashCode() {
+        /* Make no attempt to deal with concurrent modifications */
+        int hash = 0;
+        final TableEntry[] table = this.getTableAcquire();
+
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry curr = ArrayUtil.getOpaque(table, i); curr != null; curr = curr.getNextOpaque()) {
+                hash += curr.hashCode();
+            }
+        }
+
+        return hash;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String toString() {
+        final StringBuilder builder = new StringBuilder(64);
+        builder.append("SingleWriterMultiReaderHashMap:{");
+
+        this.forEach((final int key, final int value) -> {
+            builder.append("{key: \"").append(key).append("\", value: \"").append(value).append("\"}");
+        });
+
+        return builder.append('}').toString();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public SWMRInt2IntHashTable clone() {
+        return new SWMRInt2IntHashTable(this.getTableAcquire().length, this.loadFactor, this);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public void forEach(final Consumer<? super SWMRInt2IntHashTable.TableEntry> action) {
+        Validate.notNull(action, "Null action");
+
+        final TableEntry[] table = this.getTableAcquire();
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry curr = ArrayUtil.getOpaque(table, i); curr != null; curr = curr.getNextOpaque()) {
+                action.accept(curr);
+            }
+        }
+    }
+
+    @FunctionalInterface
+    public static interface BiIntIntConsumer {
+        public void accept(final int key, final int value);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public void forEach(final BiIntIntConsumer action) {
+        Validate.notNull(action, "Null action");
+
+        final TableEntry[] table = this.getTableAcquire();
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry curr = ArrayUtil.getOpaque(table, i); curr != null; curr = curr.getNextOpaque()) {
+                final int value = curr.getValueAcquire();
+
+                action.accept(curr.key, value);
+            }
+        }
+    }
+
+    /**
+     * Provides the specified consumer with all keys contained within this map.
+     * @param action The specified consumer.
+     */
+    public void forEachKey(final IntConsumer action) {
+        Validate.notNull(action, "Null action");
+
+        final TableEntry[] table = this.getTableAcquire();
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry curr = ArrayUtil.getOpaque(table, i); curr != null; curr = curr.getNextOpaque()) {
+                action.accept(curr.key);
+            }
+        }
+    }
+
+    /**
+     * Provides the specified consumer with all values contained within this map. Equivalent to {@code map.values().forEach(Consumer)}.
+     * @param action The specified consumer.
+     */
+    public void forEachValue(final IntConsumer action) {
+        Validate.notNull(action, "Null action");
+
+        final TableEntry[] table = this.getTableAcquire();
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry curr = ArrayUtil.getOpaque(table, i); curr != null; curr = curr.getNextOpaque()) {
+                final int value = curr.getValueAcquire();
+
+                action.accept(value);
+            }
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int get(final int key) {
+        final TableEntry entry = this.getEntryForOpaque(key);
+        return entry == null ? 0 : entry.getValueAcquire();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean containsKey(final int key) {
+        final TableEntry entry = this.getEntryForOpaque(key);
+        return entry != null;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int getOrDefault(final int key, final int defaultValue) {
+        final TableEntry entry = this.getEntryForOpaque(key);
+
+        return entry == null ? defaultValue : entry.getValueAcquire();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int size() {
+        return this.getSizeAcquire();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean isEmpty() {
+        return this.getSizeAcquire() == 0;
+    }
+
+    /* Non-MT-Safe */
+
+    protected int threshold;
+
+    protected final void checkResize(final int minCapacity) {
+        if (minCapacity <= this.threshold || this.threshold < 0) {
+            return;
+        }
+
+        final TableEntry[] table = this.getTablePlain();
+        int newCapacity = minCapacity >= MAXIMUM_CAPACITY ? MAXIMUM_CAPACITY : IntegerUtil.roundCeilLog2(minCapacity);
+        if (newCapacity < 0) {
+            newCapacity = MAXIMUM_CAPACITY;
+        }
+        if (newCapacity <= table.length) {
+            if (newCapacity == MAXIMUM_CAPACITY) {
+                return;
+            }
+            newCapacity = table.length << 1;
+        }
+
+        //noinspection unchecked
+        final TableEntry[] newTable = new TableEntry[newCapacity];
+        final int indexMask = newCapacity - 1;
+
+        for (int i = 0, len = table.length; i < len; ++i) {
+            for (TableEntry entry = table[i]; entry != null; entry = entry.getNextPlain()) {
+                final int key = entry.key;
+                final int hash = SWMRInt2IntHashTable.getHash(key);
+                final int index = hash & indexMask;
+
+                /* we need to create a new entry since there could be reading threads */
+                final TableEntry insert = new TableEntry(key, entry.getValuePlain());
+
+                final TableEntry prev = newTable[index];
+
+                newTable[index] = insert;
+                insert.setNextPlain(prev);
+            }
+        }
+
+        if (newCapacity == MAXIMUM_CAPACITY) {
+            this.threshold = -1; /* No more resizing */
+        } else {
+            this.threshold = getTargetCapacity(newCapacity, this.loadFactor);
+        }
+        this.setTableRelease(newTable); /* use release to publish entries in table */
+    }
+
+    protected final int addToSize(final int num) {
+        final int newSize = this.getSizePlain() + num;
+
+        this.setSizeOpaque(newSize);
+        this.checkResize(newSize);
+
+        return newSize;
+    }
+
+    protected final int removeFromSize(final int num) {
+        final int newSize = this.getSizePlain() - num;
+
+        this.setSizeOpaque(newSize);
+
+        return newSize;
+    }
+
+    protected final int put(final int key, final int value, final boolean onlyIfAbsent) {
+        final TableEntry[] table = this.getTablePlain();
+        final int hash = SWMRInt2IntHashTable.getHash(key);
+        final int index = hash & (table.length - 1);
+
+        final TableEntry head = table[index];
+        if (head == null) {
+            final TableEntry insert = new TableEntry(key, value);
+            ArrayUtil.setRelease(table, index, insert);
+            this.addToSize(1);
+            return 0;
+        }
+
+        for (TableEntry curr = head;;) {
+            if (key == curr.key) {
+                if (onlyIfAbsent) {
+                    return curr.getValuePlain();
+                }
+
+                final int currVal = curr.getValuePlain();
+                curr.setValueRelease(value);
+                return currVal;
+            }
+
+            final TableEntry next = curr.getNextPlain();
+            if (next != null) {
+                curr = next;
+                continue;
+            }
+
+            final TableEntry insert = new TableEntry(key, value);
+
+            curr.setNextRelease(insert);
+            this.addToSize(1);
+            return 0;
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int put(final int key, final int value) {
+        return this.put(key, value, false);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int putIfAbsent(final int key, final int value) {
+        return this.put(key, value, true);
+    }
+
+    protected final int remove(final int key, final int hash) {
+        final TableEntry[] table = this.getTablePlain();
+        final int index = (table.length - 1) & hash;
+
+        final TableEntry head = table[index];
+        if (head == null) {
+            return 0;
+        }
+
+        if (head.key == key) {
+            ArrayUtil.setRelease(table, index, head.getNextPlain());
+            this.removeFromSize(1);
+
+            return head.getValuePlain();
+        }
+
+        for (TableEntry curr = head.getNextPlain(), prev = head; curr != null; prev = curr, curr = curr.getNextPlain()) {
+            if (key == curr.key) {
+                prev.setNextRelease(curr.getNextPlain());
+                this.removeFromSize(1);
+
+                return curr.getValuePlain();
+            }
+        }
+
+        return 0;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public int remove(final int key) {
+        return this.remove(key, SWMRInt2IntHashTable.getHash(key));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public void putAll(final SWMRInt2IntHashTable map) {
+        Validate.notNull(map, "Null map");
+
+        final int size = map.size();
+        this.checkResize(Math.max(this.getSizePlain() + size/2, size)); /* preemptively resize */
+        map.forEach(this::put);
+    }
+
+    /**
+     * {@inheritDoc}
+     * <p>
+     * This call is non-atomic and the order that which entries are removed is undefined. The clear operation itself
+     * is release ordered, that is, after the clear operation is performed a release fence is performed.
+     * </p>
+     */
+    public void clear() {
+        Arrays.fill(this.getTablePlain(), null);
+        this.setSizeRelease(0);
+    }
+
+    public static final class TableEntry {
+
+        protected final int key;
+        protected int value;
+
+        protected TableEntry next;
+
+        protected static final VarHandle VALUE_HANDLE = ConcurrentUtil.getVarHandle(TableEntry.class, "value", Object.class);
+        protected static final VarHandle NEXT_HANDLE = ConcurrentUtil.getVarHandle(TableEntry.class, "next", TableEntry.class);
+
+        /* value */
+
+        protected final int getValuePlain() {
+            //noinspection unchecked
+            return (int)VALUE_HANDLE.get(this);
+        }
+
+        protected final int getValueAcquire() {
+            //noinspection unchecked
+            return (int)VALUE_HANDLE.getAcquire(this);
+        }
+
+        protected final void setValueRelease(final int to) {
+            VALUE_HANDLE.setRelease(this, to);
+        }
+
+        /* next */
+
+        protected final TableEntry getNextPlain() {
+            //noinspection unchecked
+            return (TableEntry)NEXT_HANDLE.get(this);
+        }
+
+        protected final TableEntry getNextOpaque() {
+            //noinspection unchecked
+            return (TableEntry)NEXT_HANDLE.getOpaque(this);
+        }
+
+        protected final void setNextPlain(final TableEntry next) {
+            NEXT_HANDLE.set(this, next);
+        }
+
+        protected final void setNextRelease(final TableEntry next) {
+            NEXT_HANDLE.setRelease(this, next);
+        }
+
+        protected TableEntry(final int key, final int value) {
+            this.key = key;
+            this.value = value;
+        }
+
+        public int getKey() {
+            return this.key;
+        }
+
+        public int getValue() {
+            return this.getValueAcquire();
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        public int setValue(final int value) {
+            final int curr = this.getValuePlain();
+
+            this.setValueRelease(value);
+            return curr;
+        }
+
+        protected static int hash(final int key, final int value) {
+            return SWMRInt2IntHashTable.getHash(key) ^ SWMRInt2IntHashTable.getHash(value);
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public int hashCode() {
+            return hash(this.key, this.getValueAcquire());
+        }
+
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public boolean equals(final Object obj) {
+            if (this == obj) {
+                return true;
+            }
+
+            if (!(obj instanceof TableEntry)) {
+                return false;
+            }
+            final TableEntry other = (TableEntry)obj;
+            final int otherKey = other.getKey();
+            final int thisKey = this.getKey();
+            final int otherValue = other.getValueAcquire();
+            final int thisVal = this.getValueAcquire();
+            return (thisKey == otherKey) && (thisVal == otherValue);
+        }
+    }
+
+}
diff --git a/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRLong2ObjectHashTable.java b/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRLong2ObjectHashTable.java
index 94fca3c9b31ca4e40688209e419e93320b0f7c34..fea1244ee156e0f562f295f31e3da288774d2f5c 100644
--- a/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRLong2ObjectHashTable.java
+++ b/src/main/java/ca/spottedleaf/concurrentutil/map/SWMRLong2ObjectHashTable.java
@@ -534,6 +534,44 @@ public class SWMRLong2ObjectHashTable<V> {
         return null;
     }
 
+    protected final V remove(final long key, final int hash, final V expect) {
+        final TableEntry<V>[] table = this.getTablePlain();
+        final int index = (table.length - 1) & hash;
+
+        final TableEntry<V> head = table[index];
+        if (head == null) {
+            return null;
+        }
+
+        if (head.key == key) {
+            final V val = head.value;
+            if (val == expect || val.equals(expect)) {
+                ArrayUtil.setRelease(table, index, head.getNextPlain());
+                this.removeFromSize(1);
+
+                return head.getValuePlain();
+            } else {
+                return null;
+            }
+        }
+
+        for (TableEntry<V> curr = head.getNextPlain(), prev = head; curr != null; prev = curr, curr = curr.getNextPlain()) {
+            if (key == curr.key) {
+                final V val = curr.value;
+                if (val == expect || val.equals(expect)) {
+                    prev.setNextRelease(curr.getNextPlain());
+                    this.removeFromSize(1);
+
+                    return curr.getValuePlain();
+                } else {
+                    return null;
+                }
+            }
+        }
+
+        return null;
+    }
+
     /**
      * {@inheritDoc}
      */
@@ -541,6 +579,10 @@ public class SWMRLong2ObjectHashTable<V> {
         return this.remove(key, SWMRLong2ObjectHashTable.getHash(key));
     }
 
+    public boolean remove(final long key, final V expect) {
+        return this.remove(key, SWMRLong2ObjectHashTable.getHash(key), expect) != null;
+    }
+
     /**
      * {@inheritDoc}
      */
diff --git a/src/main/java/ca/spottedleaf/concurrentutil/scheduler/SchedulerThreadPool.java b/src/main/java/ca/spottedleaf/concurrentutil/scheduler/SchedulerThreadPool.java
new file mode 100644
index 0000000000000000000000000000000000000000..0ce825d7af2a1dbeac5c22640534ee1901edce20
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/concurrentutil/scheduler/SchedulerThreadPool.java
@@ -0,0 +1,543 @@
+package ca.spottedleaf.concurrentutil.scheduler;
+
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import ca.spottedleaf.concurrentutil.util.TimeUtil;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.util.TraceUtil;
+import io.papermc.paper.util.set.LinkedSortedSet;
+import org.slf4j.Logger;
+import java.lang.invoke.VarHandle;
+import java.util.BitSet;
+import java.util.Comparator;
+import java.util.PriorityQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.LockSupport;
+import java.util.function.BooleanSupplier;
+
+public class SchedulerThreadPool {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    public static final long DEADLINE_NOT_SET = Long.MIN_VALUE;
+
+    private static final Comparator<SchedulableTick> TICK_COMPARATOR_BY_TIME = (final SchedulableTick t1, final SchedulableTick t2) -> {
+        final int timeCompare = TimeUtil.compareTimes(t1.scheduledStart, t2.scheduledStart);
+        if (timeCompare != 0) {
+            return timeCompare;
+        }
+
+        return Long.compare(t1.id, t2.id);
+    };
+
+    private final TickThreadRunner[] runners;
+    private final Thread[] threads;
+    private final LinkedSortedSet<SchedulableTick> awaiting = new LinkedSortedSet<>(TICK_COMPARATOR_BY_TIME);
+    private final PriorityQueue<SchedulableTick> queued = new PriorityQueue<>(TICK_COMPARATOR_BY_TIME);
+    private final BitSet idleThreads;
+
+    private final Object scheduleLock = new Object();
+
+    private volatile boolean halted;
+
+    public SchedulerThreadPool(final int threads, final ThreadFactory threadFactory) {
+        final BitSet idleThreads = new BitSet(threads);
+        for (int i = 0; i < threads; ++i) {
+            idleThreads.set(i);
+        }
+        this.idleThreads = idleThreads;
+
+        final TickThreadRunner[] runners = new TickThreadRunner[threads];
+        final Thread[] t = new Thread[threads];
+        for (int i = 0; i < threads; ++i) {
+            runners[i] = new TickThreadRunner(i, this);
+            t[i] = threadFactory.newThread(runners[i]);
+        }
+
+        this.threads = t;
+        this.runners = runners;
+    }
+
+    /**
+     * Starts the threads in this pool.
+     */
+    public void start() {
+        for (final Thread thread : this.threads) {
+            thread.start();
+        }
+    }
+
+    /**
+     * Attempts to prevent further execution of tasks, optionally waiting for the scheduler threads to die.
+     *
+     * @param sync Whether to wait for the scheduler threads to die.
+     * @param maxWaitNS The maximum time, in ns, to wait for the scheduler threads to die.
+     * @return {@code true} if sync was false, or if sync was true and the scheduler threads died before the timeout.
+     *          Otherwise, returns {@code false} if the time elapsed exceeded the maximum wait time.
+     */
+    public boolean halt(final boolean sync, final long maxWaitNS) {
+        this.halted = true;
+        for (final Thread thread : this.threads) {
+            // force response to halt
+            LockSupport.unpark(thread);
+        }
+        final long time = System.nanoTime();
+        if (sync) {
+            // start at 10 * 0.5ms -> 5ms
+            for (long failures = 9L;; failures = ConcurrentUtil.linearLongBackoff(failures, 500_000L, 50_000_000L)) {
+                boolean allDead = true;
+                for (final Thread thread : this.threads) {
+                    if (thread.isAlive()) {
+                        allDead = false;
+                        break;
+                    }
+                }
+                if (allDead) {
+                    return true;
+                }
+                if ((System.nanoTime() - time) >= maxWaitNS) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    public void dumpAliveThreadTraces(final String reason) {
+        for (final Thread thread : this.threads) {
+            if (thread.isAlive()) {
+                TraceUtil.dumpTraceForThread(thread, reason);
+            }
+        }
+    }
+
+    /**
+     * Returns an array of the underlying scheduling threads.
+     */
+    public Thread[] getThreads() {
+        return this.threads.clone();
+    }
+
+    private void insertFresh(final SchedulableTick task) {
+        final TickThreadRunner[] runners = this.runners;
+
+        final int firstIdleThread = this.idleThreads.nextSetBit(0);
+
+        if (firstIdleThread != -1) {
+            // push to idle thread
+            this.idleThreads.clear(firstIdleThread);
+            final TickThreadRunner runner = runners[firstIdleThread];
+            task.awaitingLink = this.awaiting.addLast(task);
+            runner.acceptTask(task);
+            return;
+        }
+
+        // try to replace the last awaiting task
+        final SchedulableTick last = this.awaiting.last();
+
+        if (last != null && TICK_COMPARATOR_BY_TIME.compare(task, last) < 0) {
+            // need to replace the last task
+            this.awaiting.pollLast();
+            last.awaitingLink = null;
+            task.awaitingLink = this.awaiting.addLast(task);
+            // need to add task to queue to be picked up later
+            this.queued.add(last);
+
+            final TickThreadRunner runner = last.ownedBy;
+            runner.replaceTask(task);
+
+            return;
+        }
+
+        // add to queue, will be picked up later
+        this.queued.add(task);
+    }
+
+    private void takeTask(final TickThreadRunner runner, final SchedulableTick tick) {
+        if (!this.awaiting.remove(tick.awaitingLink)) {
+            throw new IllegalStateException("Task is not in awaiting");
+        }
+        tick.awaitingLink = null;
+    }
+
+    private SchedulableTick returnTask(final TickThreadRunner runner, final SchedulableTick reschedule) {
+        if (reschedule != null) {
+            this.queued.add(reschedule);
+        }
+        final SchedulableTick ret = this.queued.poll();
+        if (ret == null) {
+            this.idleThreads.set(runner.id);
+        } else {
+            ret.awaitingLink = this.awaiting.addLast(ret);
+        }
+
+        return ret;
+    }
+
+    public void schedule(final SchedulableTick task) {
+        synchronized (this.scheduleLock) {
+            if (!task.tryMarkScheduled()) {
+                throw new IllegalStateException("Task " + task + " is already scheduled or cancelled");
+            }
+
+            task.schedulerOwnedBy = this;
+
+            this.insertFresh(task);
+        }
+    }
+
+    public boolean updateTickStartToMax(final SchedulableTick task, final long newStart) {
+        synchronized (this.scheduleLock) {
+            if (TimeUtil.compareTimes(newStart, task.getScheduledStart()) <= 0) {
+                return false;
+            }
+            if (this.queued.remove(task)) {
+                task.setScheduledStart(newStart);
+                this.queued.add(task);
+                return true;
+            }
+            if (task.awaitingLink != null) {
+                this.awaiting.remove(task.awaitingLink);
+                task.awaitingLink = null;
+
+                // re-queue task
+                task.setScheduledStart(newStart);
+                this.queued.add(task);
+
+                // now we need to replace the task the runner was waiting for
+                final TickThreadRunner runner = task.ownedBy;
+                final SchedulableTick replace = this.queued.poll();
+
+                // replace cannot be null, since we have added a task to queued
+                if (replace != task) {
+                    runner.replaceTask(replace);
+                }
+
+                return true;
+            }
+
+            return false;
+        }
+    }
+
+    /**
+     * Returns {@code null} if the task is not scheduled, returns {@code TRUE} if the task was cancelled
+     * and was queued to execute, returns {@code FALSE} if the task was cancelled but was executing.
+     */
+    public Boolean tryRetire(final SchedulableTick task) {
+        if (task.schedulerOwnedBy != this) {
+            return null;
+        }
+
+        synchronized (this.scheduleLock) {
+            if (this.queued.remove(task)) {
+                // cancelled, and no runner owns it - so return
+                return Boolean.TRUE;
+            }
+            if (task.awaitingLink != null) {
+                this.awaiting.remove(task.awaitingLink);
+                task.awaitingLink = null;
+                // here we need to replace the task the runner was waiting for
+                final TickThreadRunner runner = task.ownedBy;
+                final SchedulableTick replace = this.queued.poll();
+
+                if (replace == null) {
+                    // nothing to replace with, set to idle
+                    this.idleThreads.set(runner.id);
+                    runner.forceIdle();
+                } else {
+                    runner.replaceTask(replace);
+                }
+
+                return Boolean.TRUE;
+            }
+
+            // could not find it in queue
+            return task.tryMarkCancelled() ? Boolean.FALSE : null;
+        }
+    }
+
+    public void notifyTasks(final SchedulableTick task) {
+        // Not implemented
+    }
+
+    /**
+     * Represents a tickable task that can be scheduled into a {@link SchedulerThreadPool}.
+     * <p>
+     * A tickable task is expected to run on a fixed interval, which is determined by
+     * the {@link SchedulerThreadPool}.
+     * </p>
+     * <p>
+     * A tickable task can have intermediate tasks that can be executed before its tick method is ran. Instead of
+     * the {@link SchedulerThreadPool} parking in-between ticks, the scheduler will instead drain
+     * intermediate tasks from scheduled tasks. The parsing of intermediate tasks allows the scheduler to take
+     * advantage of downtime to reduce the intermediate task load from tasks once they begin ticking.
+     * </p>
+     * <p>
+     * It is guaranteed that {@link #runTick()} and {@link #runTasks(BooleanSupplier)} are never
+     * invoked in parallel.
+     * It is required that when intermediate tasks are scheduled, that {@link SchedulerThreadPool#notifyTasks(SchedulableTick)}
+     * is invoked for any scheduled task - otherwise, {@link #runTasks(BooleanSupplier)} may not be invoked to
+     * parse intermediate tasks.
+     * </p>
+     */
+    public static abstract class SchedulableTick {
+        private static final AtomicLong ID_GENERATOR = new AtomicLong();
+        public final long id = ID_GENERATOR.getAndIncrement();
+
+        private static final int SCHEDULE_STATE_NOT_SCHEDULED = 0;
+        private static final int SCHEDULE_STATE_SCHEDULED = 1;
+        private static final int SCHEDULE_STATE_CANCELLED = 2;
+
+        private final AtomicInteger scheduled = new AtomicInteger();
+        private SchedulerThreadPool schedulerOwnedBy;
+        private long scheduledStart = DEADLINE_NOT_SET;
+        private TickThreadRunner ownedBy;
+
+        private LinkedSortedSet.Link<SchedulableTick> awaitingLink;
+
+        private boolean tryMarkScheduled() {
+            return this.scheduled.compareAndSet(SCHEDULE_STATE_NOT_SCHEDULED, SCHEDULE_STATE_SCHEDULED);
+        }
+
+        private boolean tryMarkCancelled() {
+            return this.scheduled.compareAndSet(SCHEDULE_STATE_SCHEDULED, SCHEDULE_STATE_CANCELLED);
+        }
+
+        private boolean isScheduled() {
+            return this.scheduled.get() == SCHEDULE_STATE_SCHEDULED;
+        }
+
+        protected final long getScheduledStart() {
+            return this.scheduledStart;
+        }
+
+        /**
+         * If this task is scheduled, then this may only be invoked during {@link #runTick()},
+         * and {@link #runTasks(BooleanSupplier)}
+         */
+        protected final void setScheduledStart(final long value) {
+            this.scheduledStart = value;
+        }
+
+        /**
+         * Executes the tick.
+         * <p>
+         * It is the callee's responsibility to invoke {@link #setScheduledStart(long)} to adjust the start of
+         * the next tick.
+         * </p>
+         * @return {@code true} if the task should continue to be scheduled, {@code false} otherwise.
+         */
+        public abstract boolean runTick();
+
+        /**
+         * Returns whether this task has any intermediate tasks that can be executed.
+         */
+        public abstract boolean hasTasks();
+
+        /**
+         * Returns {@code null} if this task should not be scheduled, otherwise returns
+         * {@code Boolean.TRUE} if there are more intermediate tasks to execute and
+         * {@code Boolean.FALSE} if there are no more intermediate tasks to execute.
+         */
+        public abstract Boolean runTasks(final BooleanSupplier canContinue);
+
+        @Override
+        public String toString() {
+            return "SchedulableTick:{" +
+                    "class=" + this.getClass().getName() + "," +
+                    "scheduled_state=" + this.scheduled.get() + ","
+                    + "}";
+        }
+    }
+
+    private static final class TickThreadRunner implements Runnable {
+
+        /**
+         * There are no tasks in this thread's runqueue, so it is parked.
+         * <p>
+         * stateTarget = null
+         * </p>
+         */
+        private static final int STATE_IDLE = 0;
+
+        /**
+         * The runner is waiting to tick a task, as it has no intermediate tasks to execute.
+         * <p>
+         * stateTarget = the task awaiting tick
+         * </p>
+         */
+        private static final int STATE_AWAITING_TICK = 1;
+
+        /**
+         * The runner is executing a tick for one of the tasks that was in its runqueue.
+         * <p>
+         * stateTarget = the task being ticked
+         * </p>
+         */
+        private static final int STATE_EXECUTING_TICK = 2;
+
+        public final int id;
+        public final SchedulerThreadPool scheduler;
+
+        private volatile Thread thread;
+        private volatile TickThreadRunnerState state = new TickThreadRunnerState(null, STATE_IDLE);
+        private static final VarHandle STATE_HANDLE = ConcurrentUtil.getVarHandle(TickThreadRunner.class, "state", TickThreadRunnerState.class);
+
+        private void setStatePlain(final TickThreadRunnerState state) {
+            STATE_HANDLE.set(this, state);
+        }
+
+        private void setStateOpaque(final TickThreadRunnerState state) {
+            STATE_HANDLE.setOpaque(this, state);
+        }
+
+        private void setStateVolatile(final TickThreadRunnerState state) {
+            STATE_HANDLE.setVolatile(this, state);
+        }
+
+        private static record TickThreadRunnerState(SchedulableTick stateTarget, int state) {}
+
+        public TickThreadRunner(final int id, final SchedulerThreadPool scheduler) {
+            this.id = id;
+            this.scheduler = scheduler;
+        }
+
+        private Thread getRunnerThread() {
+            return this.thread;
+        }
+
+        private void acceptTask(final SchedulableTick task) {
+            if (task.ownedBy != null) {
+                throw new IllegalStateException("Already owned by another runner");
+            }
+            task.ownedBy = this;
+            final TickThreadRunnerState state = this.state;
+            if (state.state != STATE_IDLE) {
+                throw new IllegalStateException("Cannot accept task in state " + state);
+            }
+            this.setStateVolatile(new TickThreadRunnerState(task, STATE_AWAITING_TICK));
+            LockSupport.unpark(this.getRunnerThread());
+        }
+
+        private void replaceTask(final SchedulableTick task) {
+            final TickThreadRunnerState state = this.state;
+            if (state.state != STATE_AWAITING_TICK) {
+                throw new IllegalStateException("Cannot replace task in state " + state);
+            }
+            if (task.ownedBy != null) {
+                throw new IllegalStateException("Already owned by another runner");
+            }
+            task.ownedBy = this;
+
+            state.stateTarget.ownedBy = null;
+
+            this.setStateVolatile(new TickThreadRunnerState(task, STATE_AWAITING_TICK));
+            LockSupport.unpark(this.getRunnerThread());
+        }
+
+        private void forceIdle() {
+            final TickThreadRunnerState state = this.state;
+            if (state.state != STATE_AWAITING_TICK) {
+                throw new IllegalStateException("Cannot replace task in state " + state);
+            }
+            state.stateTarget.ownedBy = null;
+            this.setStateOpaque(new TickThreadRunnerState(null, STATE_IDLE));
+            // no need to unpark
+        }
+
+        private boolean takeTask(final TickThreadRunnerState state, final SchedulableTick task) {
+            synchronized (this.scheduler.scheduleLock) {
+                if (this.state != state) {
+                    return false;
+                }
+                this.setStatePlain(new TickThreadRunnerState(task, STATE_EXECUTING_TICK));
+                this.scheduler.takeTask(this, task);
+                return true;
+            }
+        }
+
+        private void returnTask(final SchedulableTick task, final boolean reschedule) {
+            synchronized (this.scheduler.scheduleLock) {
+                task.ownedBy = null;
+
+                final SchedulableTick newWait = this.scheduler.returnTask(this, reschedule && task.isScheduled() ? task : null);
+                if (newWait == null) {
+                    this.setStatePlain(new TickThreadRunnerState(null, STATE_IDLE));
+                } else {
+                    if (newWait.ownedBy != null) {
+                        throw new IllegalStateException("Already owned by another runner");
+                    }
+                    newWait.ownedBy = this;
+                    this.setStatePlain(new TickThreadRunnerState(newWait, STATE_AWAITING_TICK));
+                }
+            }
+        }
+
+        @Override
+        public void run() {
+            this.thread = Thread.currentThread();
+
+            main_state_loop:
+            for (;;) {
+                final TickThreadRunnerState startState = this.state;
+                final int startStateType = startState.state;
+                final SchedulableTick startStateTask =  startState.stateTarget;
+
+                if (this.scheduler.halted) {
+                    return;
+                }
+
+                switch (startStateType) {
+                    case STATE_IDLE: {
+                        while (this.state.state == STATE_IDLE) {
+                            LockSupport.park();
+                            if (this.scheduler.halted) {
+                                return;
+                            }
+                        }
+                        continue main_state_loop;
+                    }
+
+                    case STATE_AWAITING_TICK: {
+                        final long deadline = startStateTask.getScheduledStart();
+                        for (;;) {
+                            if (this.state != startState) {
+                                continue main_state_loop;
+                            }
+                            final long diff = deadline - System.nanoTime();
+                            if (diff <= 0L) {
+                                break;
+                            }
+                            LockSupport.parkNanos(startState, diff);
+                            if (this.scheduler.halted) {
+                                return;
+                            }
+                        }
+
+                        if (!this.takeTask(startState, startStateTask)) {
+                            continue main_state_loop;
+                        }
+
+                        // TODO exception handling
+                        final boolean reschedule = startStateTask.runTick();
+
+                        this.returnTask(startStateTask, reschedule);
+
+                        continue main_state_loop;
+                    }
+
+                    case STATE_EXECUTING_TICK: {
+                        throw new IllegalStateException("Tick execution must be set by runner thread, not by any other thread");
+                    }
+
+                    default: {
+                        throw new IllegalStateException("Unknown state: " + startState);
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/concurrentutil/util/TimeUtil.java b/src/main/java/ca/spottedleaf/concurrentutil/util/TimeUtil.java
new file mode 100644
index 0000000000000000000000000000000000000000..63688716244066581d5b505703576e3340e3baf3
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/concurrentutil/util/TimeUtil.java
@@ -0,0 +1,60 @@
+package ca.spottedleaf.concurrentutil.util;
+
+public final class TimeUtil {
+
+    /*
+     * The comparator is not a valid comparator for every long value. To prove where it is valid, see below.
+     *
+     * For reflexivity, we have that x - x = 0. We then have that for any long value x that
+     * compareTimes(x, x) == 0, as expected.
+     *
+     * For symmetry, we have that x - y = -(y - x) except for when y - x = Long.MIN_VALUE.
+     * So, the difference between any times x and y must not be equal to Long.MIN_VALUE.
+     *
+     * As for the transitive relation, consider we have x,y such that x - y = a > 0 and z such that
+     * y - z = b > 0. Then, we will have that the x - z > 0 is equivalent to a + b > 0. For long values,
+     * this holds as long as a + b <= Long.MAX_VALUE.
+     *
+     * Also consider we have x, y such that x - y = a < 0 and z such that y - z = b < 0. Then, we will have
+     * that x - z < 0 is equivalent to a + b < 0. For long values, this holds as long as a + b >= -Long.MAX_VALUE.
+     *
+     * Thus, the comparator is only valid for timestamps such that abs(c - d) <= Long.MAX_VALUE for all timestamps
+     * c and d.
+     */
+
+    /**
+     * This function is appropriate to be used as a {@link java.util.Comparator} between two timestamps, which
+     * indicates whether the timestamps represented by t1, t2 that t1 is before, equal to, or after t2.
+     */
+    public static int compareTimes(final long t1, final long t2) {
+        final long diff = t1 - t2;
+
+        // HD, Section 2-7
+        return (int) ((diff >> 63) | (-diff >>> 63));
+    }
+
+    public static long getGreatestTime(final long t1, final long t2) {
+        final long diff = t1 - t2;
+        return diff < 0L ? t2 : t1;
+    }
+
+    public static long getLeastTime(final long t1, final long t2) {
+        final long diff = t1 - t2;
+        return diff > 0L ? t2 : t1;
+    }
+
+    public static long clampTime(final long value, final long min, final long max) {
+        final long diffMax = value - max;
+        final long diffMin = value - min;
+
+        if (diffMax > 0L) {
+            return max;
+        }
+        if (diffMin < 0L) {
+            return min;
+        }
+        return value;
+    }
+
+    private TimeUtil() {}
+}
diff --git a/src/main/java/com/destroystokyo/paper/util/RedstoneWireTurbo.java b/src/main/java/com/destroystokyo/paper/util/RedstoneWireTurbo.java
index fa062e6543e8a0377e3d4715996955dba005ee80..6284262d8cc2a07ad43eb46c888ca647613c926a 100644
--- a/src/main/java/com/destroystokyo/paper/util/RedstoneWireTurbo.java
+++ b/src/main/java/com/destroystokyo/paper/util/RedstoneWireTurbo.java
@@ -833,14 +833,14 @@ public class RedstoneWireTurbo {
         j = getMaxCurrentStrength(upd, j);
         int l = 0;
 
-        wire.shouldSignal = false;
+        io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal = false; // Folia - region threading
         // Unfortunately, World.isBlockIndirectlyGettingPowered is complicated,
         // and I'm not ready to try to replicate even more functionality from
         // elsewhere in Minecraft into this accelerator.  So sadly, we must
         // suffer the performance hit of this very expensive call.  If there
         // is consistency to what this call returns, we may be able to cache it.
         final int k = worldIn.getBestNeighborSignal(upd.self);
-        wire.shouldSignal = true;
+        io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal = true; // Folia - region threading
 
         // The variable 'k' holds the maximum redstone power value of any adjacent blocks.
         // If 'k' has the highest level of all neighbors, then the power level of this
diff --git a/src/main/java/io/papermc/paper/adventure/ChatProcessor.java b/src/main/java/io/papermc/paper/adventure/ChatProcessor.java
index 1d78e8beacbc93ef2cd6beb418edca843f8a5429..ccf869d2dcd788c8264589fa4205448855a49dfd 100644
--- a/src/main/java/io/papermc/paper/adventure/ChatProcessor.java
+++ b/src/main/java/io/papermc/paper/adventure/ChatProcessor.java
@@ -83,7 +83,7 @@ public final class ChatProcessor {
             final CraftPlayer player = this.player.getBukkitEntity();
             final AsyncPlayerChatEvent ae = new AsyncPlayerChatEvent(this.async, player, this.craftbukkit$originalMessage, new LazyPlayerSet(this.server));
             this.post(ae);
-            if (listenersOnSyncEvent) {
+            if (false && listenersOnSyncEvent) { // Folia - region threading
                 final PlayerChatEvent se = new PlayerChatEvent(player, ae.getMessage(), ae.getFormat(), ae.getRecipients());
                 se.setCancelled(ae.isCancelled()); // propagate cancelled state
                 this.queueIfAsyncOrRunImmediately(new Waitable<Void>() {
@@ -150,7 +150,7 @@ public final class ChatProcessor {
         ae.setCancelled(cancelled); // propagate cancelled state
         this.post(ae);
         final boolean listenersOnSyncEvent = canYouHearMe(ChatEvent.getHandlerList());
-        if (listenersOnSyncEvent) {
+        if (false && listenersOnSyncEvent) { // Folia - region threading
             this.queueIfAsyncOrRunImmediately(new Waitable<Void>() {
                 @Override
                 protected Void evaluate() {
diff --git a/src/main/java/io/papermc/paper/adventure/providers/ClickCallbackProviderImpl.java b/src/main/java/io/papermc/paper/adventure/providers/ClickCallbackProviderImpl.java
index 23432eea862c6df716d7726a32da3a0612a3fb77..f59e8bb72c5233f26a8a0d506ac64bb37fef97a5 100644
--- a/src/main/java/io/papermc/paper/adventure/providers/ClickCallbackProviderImpl.java
+++ b/src/main/java/io/papermc/paper/adventure/providers/ClickCallbackProviderImpl.java
@@ -23,35 +23,42 @@ public class ClickCallbackProviderImpl implements ClickCallback.Provider {
 
     public static final class CallbackManager {
 
-        private final Map<UUID, StoredCallback> callbacks = new HashMap<>();
-        private final Queue<StoredCallback> queue = new ConcurrentLinkedQueue<>();
+        private final java.util.concurrent.ConcurrentHashMap<UUID, StoredCallback> callbacks = new java.util.concurrent.ConcurrentHashMap<>(); // Folia - region threading
+        // Folia - region threading
 
         private CallbackManager() {
         }
 
         public UUID addCallback(final @NotNull ClickCallback<Audience> callback, final ClickCallback.@NotNull Options options) {
             final UUID id = UUID.randomUUID();
-            this.queue.add(new StoredCallback(callback, options, id));
+            final StoredCallback scb = new StoredCallback(callback, options, id); // Folia - region threading
+            this.callbacks.put(scb.id(), scb); // Folia - region threading
             return id;
         }
 
         public void handleQueue(final int currentTick) {
             // Evict expired entries
             if (currentTick % 100 == 0) {
-                this.callbacks.values().removeIf(callback -> !callback.valid());
+                this.callbacks.values().removeIf(StoredCallback::expired); // Folia - region threading - don't read uses field
             }
 
-            // Add entries from queue
-            StoredCallback callback;
-            while ((callback = this.queue.poll()) != null) {
-                this.callbacks.put(callback.id(), callback);
-            }
+            // Folia - region threading
         }
 
         public void runCallback(final @NotNull Audience audience, final UUID id) {
-            final StoredCallback callback = this.callbacks.get(id);
-            if (callback != null && callback.valid()) { //TODO Message if expired/invalid?
-                callback.takeUse();
+            // Folia start - region threading
+            final StoredCallback[] use = new StoredCallback[1];
+            this.callbacks.computeIfPresent(id, (final UUID keyInMap, final StoredCallback value) -> {
+                if (!value.valid()) {
+                    return null;
+                }
+                use[0] = value;
+                value.takeUse();
+                return value.valid() ? value : null;
+            });
+            final StoredCallback callback = use[0];
+            if (callback != null) { //TODO Message if expired/invalid?
+                // Folia end - region threading
                 callback.callback.accept(audience);
             }
         }
diff --git a/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java b/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java
index cbeaadaecf816070b3a37938c8e683180939afc4..f1991bbce762df848726d2f0b6f1d01765be9ba5 100644
--- a/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java
+++ b/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java
@@ -82,6 +82,9 @@ public final class ChunkSystem {
         for (int index = 0, len = chunkMap.regionManagers.size(); index < len; ++index) {
             chunkMap.regionManagers.get(index).addChunk(holder.getPos().x, holder.getPos().z);
         }
+        // Folia start - threaded regions
+        level.regioniser.addChunk(holder.pos.x, holder.pos.z);
+        // Folia end - threaded regions
     }
 
     public static void onChunkHolderDelete(final ServerLevel level, final ChunkHolder holder) {
@@ -89,34 +92,39 @@ public final class ChunkSystem {
         for (int index = 0, len = chunkMap.regionManagers.size(); index < len; ++index) {
             chunkMap.regionManagers.get(index).removeChunk(holder.getPos().x, holder.getPos().z);
         }
+        // Folia start - threaded regions
+        level.regioniser.removeChunk(holder.pos.x, holder.pos.z);
+        // Folia end - threaded regions
     }
 
     public static void onChunkBorder(final LevelChunk chunk, final ChunkHolder holder) {
         chunk.playerChunk = holder;
         chunk.chunkStatus = net.minecraft.server.level.FullChunkStatus.FULL;
+        chunk.level.getCurrentWorldData().addChunk(chunk); // Folia - region threading
     }
 
     public static void onChunkNotBorder(final LevelChunk chunk, final ChunkHolder holder) {
         chunk.chunkStatus = net.minecraft.server.level.FullChunkStatus.INACCESSIBLE;
+        chunk.level.getCurrentWorldData().removeChunk(chunk); // Folia - region threading
     }
 
     public static void onChunkTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().tickingChunks.add(chunk);
+        chunk.level.getCurrentWorldData().addTickingChunk(chunk); // Folia - region threading
         chunk.chunkStatus = net.minecraft.server.level.FullChunkStatus.BLOCK_TICKING;
     }
 
     public static void onChunkNotTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().tickingChunks.remove(chunk);
+        chunk.level.getCurrentWorldData().removeTickingChunk(chunk); // Folia - region threading
         chunk.chunkStatus = net.minecraft.server.level.FullChunkStatus.FULL;
     }
 
     public static void onChunkEntityTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().entityTickingChunks.add(chunk);
+        chunk.level.getCurrentWorldData().addEntityTickingChunk(chunk); // Folia - region threading
         chunk.chunkStatus = net.minecraft.server.level.FullChunkStatus.ENTITY_TICKING;
     }
 
     public static void onChunkNotEntityTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().entityTickingChunks.remove(chunk);
+        chunk.level.getCurrentWorldData().removeEntityTickingChunk(chunk); // Folia - region threading
         chunk.chunkStatus = net.minecraft.server.level.FullChunkStatus.BLOCK_TICKING;
     }
 
diff --git a/src/main/java/io/papermc/paper/chunk/system/RegionizedPlayerChunkLoader.java b/src/main/java/io/papermc/paper/chunk/system/RegionizedPlayerChunkLoader.java
index bf3c5efa0d58c58a5b0b6b73880aaf03c8a37c12..a45dda1f81d250340ad0d8d7998e79d083dc7ebd 100644
--- a/src/main/java/io/papermc/paper/chunk/system/RegionizedPlayerChunkLoader.java
+++ b/src/main/java/io/papermc/paper/chunk/system/RegionizedPlayerChunkLoader.java
@@ -141,6 +141,7 @@ public class RegionizedPlayerChunkLoader {
     public void updatePlayer(final ServerPlayer player) {
         final PlayerChunkLoaderData loader = player.chunkLoader;
         if (loader != null) {
+            player.serverLevel().chunkSource.chunkMap.getNearbyPlayers().tickPlayer(player); // Folia - region threading
             loader.update();
         }
     }
@@ -154,7 +155,7 @@ public class RegionizedPlayerChunkLoader {
         final PlayerChunkLoaderData loader = player.chunkLoader;
 
         if (loader == null) {
-            return;
+            throw new IllegalStateException("Player is already removed from player chunk loader"); // Folia - region threading
         }
 
         loader.remove();
@@ -233,7 +234,7 @@ public class RegionizedPlayerChunkLoader {
     public void tick() {
         TickThread.ensureTickThread("Cannot tick player chunk loader async");
         long currTime = System.nanoTime();
-        for (final ServerPlayer player : new java.util.ArrayList<>(this.world.players())) {
+        for (final ServerPlayer player : new java.util.ArrayList<>(this.world.getLocalPlayers())) { // Folia - region threding
             final PlayerChunkLoaderData loader = player.chunkLoader;
             if (loader == null || loader.world != this.world) {
                 // not our problem anymore
diff --git a/src/main/java/io/papermc/paper/chunk/system/entity/EntityLookup.java b/src/main/java/io/papermc/paper/chunk/system/entity/EntityLookup.java
index 15ee41452992714108efe53b708b5a4e1da7c1ff..5bef4f50082e56b89239cfd62dd7429926b71c09 100644
--- a/src/main/java/io/papermc/paper/chunk/system/entity/EntityLookup.java
+++ b/src/main/java/io/papermc/paper/chunk/system/entity/EntityLookup.java
@@ -191,7 +191,12 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
 
     @Override
     public Iterable<Entity> getAll() {
-        return new ArrayIterable<>(this.accessibleEntities.getRawData(), 0, this.accessibleEntities.size());
+        // Folia start - region threading
+        synchronized (this.accessibleEntities) {
+            Entity[] iterate = java.util.Arrays.copyOf(this.accessibleEntities.getRawData(), this.accessibleEntities.size());
+            return new ArrayIterable<>(iterate, 0, iterate.length);
+        }
+        // Folia end - region threading
     }
 
     public Entity[] getAllCopy() {
@@ -277,7 +282,9 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
                     if (newVisibility.ordinal() > oldVisibility.ordinal()) {
                         // status upgrade
                         if (!oldVisibility.isAccessible() && newVisibility.isAccessible()) {
+                            synchronized (this.accessibleEntities) { // Folia - region threading
                             this.accessibleEntities.add(entity);
+                            } // Folia - region threading
                             EntityLookup.this.worldCallback.onTrackingStart(entity);
                         }
 
@@ -291,7 +298,9 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
                         }
 
                         if (oldVisibility.isAccessible() && !newVisibility.isAccessible()) {
+                            synchronized (this.accessibleEntities) { // Folia - region threading
                             this.accessibleEntities.remove(entity);
+                            } // Folia - region threading
                             EntityLookup.this.worldCallback.onTrackingEnd(entity);
                         }
                     }
@@ -434,6 +443,8 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
 
         entity.setLevelCallback(new EntityCallback(entity));
 
+        this.world.getCurrentWorldData().addEntity(entity); // Folia - region threading
+
         this.entityStatusChange(entity, slices, Visibility.HIDDEN, getEntityStatus(entity), false, !fromDisk, false);
 
         return true;
@@ -450,6 +461,19 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
         return slices == null || !slices.isPreventingStatusUpdates();
     }
 
+    // Folia start - region threading
+    // only appropriate to use when in shutdown, as this performs no logic hooks to properly add to world
+    public boolean addEntityForShutdownTeleportComplete(final Entity entity) {
+        final BlockPos pos = entity.blockPosition();
+        final int sectionX = pos.getX() >> 4;
+        final int sectionY = Mth.clamp(pos.getY() >> 4, this.minSection, this.maxSection);
+        final int sectionZ = pos.getZ() >> 4;
+        final ChunkEntitySlices slices = this.getOrCreateChunk(sectionX, sectionZ);
+
+        return slices.addEntity(entity, sectionY);
+    }
+    // Folia end - region threading
+
     private void removeEntity(final Entity entity) {
         final int sectionX = entity.sectionX;
         final int sectionY = entity.sectionY;
@@ -864,12 +888,18 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
         @Override
         public void onMove() {
             final Entity entity = this.entity;
+            final io.papermc.paper.threadedregions.RegionizedWorldData regionData = entity.level().getCurrentWorldData(); // Folia - region threading
             final Visibility oldVisibility = getEntityStatus(entity);
             final ChunkEntitySlices newSlices = EntityLookup.this.moveEntity(this.entity);
             if (newSlices == null) {
                 // no new section, so didn't change sections
                 return;
             }
+            // Folia start - region threading
+            if (entity instanceof net.minecraft.server.level.ServerPlayer player) {
+                regionData.getNearbyPlayers().tickPlayer(player);
+            }
+            // Folia end - region threading
             final Visibility newVisibility = getEntityStatus(entity);
 
             EntityLookup.this.entityStatusChange(entity, newSlices, oldVisibility, newVisibility, true, false, false);
@@ -886,6 +916,9 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
             EntityLookup.this.entityStatusChange(entity, null, tickingState, Visibility.HIDDEN, false, false, reason.shouldDestroy());
 
             this.entity.setLevelCallback(NoOpCallback.INSTANCE);
+
+            // only AFTER full removal callbacks, so that thread checking will work. // Folia - region threading
+            EntityLookup.this.world.getCurrentWorldData().removeEntity(entity); // Folia - region threading
         }
     }
 
diff --git a/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkHolderManager.java b/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkHolderManager.java
index 6bc7c6f16a1649fc9e24e7cf90fca401e5bd4875..67bf841878eb8e3703782caeb16db4803d13f0d9 100644
--- a/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkHolderManager.java
+++ b/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkHolderManager.java
@@ -53,6 +53,14 @@ import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.LockSupport;
 import java.util.function.Predicate;
 
+// Folia start - region threading
+import io.papermc.paper.threadedregions.RegionizedServer;
+import io.papermc.paper.threadedregions.ThreadedRegionizer;
+import io.papermc.paper.threadedregions.TickRegionScheduler;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
+// Folia end - region threading
+
 public final class ChunkHolderManager {
 
     private static final Logger LOGGER = LogUtils.getClassLogger();
@@ -112,27 +120,83 @@ public final class ChunkHolderManager {
     private final ChunkTaskScheduler taskScheduler;
     private long currentTick;
 
-    private final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = new ArrayDeque<>();
-    private final ObjectRBTreeSet<NewChunkHolder> autoSaveQueue = new ObjectRBTreeSet<>((final NewChunkHolder c1, final NewChunkHolder c2) -> {
-        if (c1 == c2) {
-            return 0;
+    // Folia start - region threading
+    public static final class HolderManagerRegionData {
+        private final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = new ArrayDeque<>();
+        private final ObjectRBTreeSet<NewChunkHolder> autoSaveQueue = new ObjectRBTreeSet<>((final NewChunkHolder c1, final NewChunkHolder c2) -> {
+            if (c1 == c2) {
+                return 0;
+            }
+
+            final int saveTickCompare = Long.compare(c1.lastAutoSave, c2.lastAutoSave);
+
+            if (saveTickCompare != 0) {
+                return saveTickCompare;
+            }
+
+            final long coord1 = CoordinateUtils.getChunkKey(c1.chunkX, c1.chunkZ);
+            final long coord2 = CoordinateUtils.getChunkKey(c2.chunkX, c2.chunkZ);
+
+            if (coord1 == coord2) {
+                throw new IllegalStateException("Duplicate chunkholder in auto save queue");
+            }
+
+            return Long.compare(coord1, coord2);
+        });
+
+        public void merge(final HolderManagerRegionData into, final long tickOffset) {
+            // Order doesn't really matter for the pending full update...
+            into.pendingFullLoadUpdate.addAll(this.pendingFullLoadUpdate);
+
+            // We need to copy the set to iterate over, because modifying the field used in compareTo while iterating
+            // will destroy the result from compareTo (However, the set is not destroyed _after_ iteration because a constant
+            // addition to every entry will not affect compareTo).
+            for (final NewChunkHolder holder : new ArrayList<>(this.autoSaveQueue)) {
+                holder.lastAutoSave += tickOffset;
+                into.autoSaveQueue.add(holder);
+            }
         }
 
-        final int saveTickCompare = Long.compare(c1.lastAutoSave, c2.lastAutoSave);
+        public void split(final int chunkToRegionShift, final Long2ReferenceOpenHashMap<HolderManagerRegionData> regionToData,
+                          final ReferenceOpenHashSet<HolderManagerRegionData> dataSet) {
+            for (final NewChunkHolder fullLoadUpdate : this.pendingFullLoadUpdate) {
+                final int regionCoordinateX = fullLoadUpdate.chunkX >> chunkToRegionShift;
+                final int regionCoordinateZ = fullLoadUpdate.chunkZ >> chunkToRegionShift;
+
+                final HolderManagerRegionData data = regionToData.get(CoordinateUtils.getChunkKey(regionCoordinateX, regionCoordinateZ));
+                if (data != null) {
+                    data.pendingFullLoadUpdate.add(fullLoadUpdate);
+                } // else: fullLoadUpdate is an unloaded chunk holder
+            }
+
+            for (final NewChunkHolder autoSave : this.autoSaveQueue) {
+                final int regionCoordinateX = autoSave.chunkX >> chunkToRegionShift;
+                final int regionCoordinateZ = autoSave.chunkZ >> chunkToRegionShift;
 
-        if (saveTickCompare != 0) {
-            return saveTickCompare;
+                final HolderManagerRegionData data = regionToData.get(CoordinateUtils.getChunkKey(regionCoordinateX, regionCoordinateZ));
+                if (data != null) {
+                    data.autoSaveQueue.add(autoSave);
+                } // else: autoSave is an unloaded chunk holder
+            }
         }
+    }
 
-        final long coord1 = CoordinateUtils.getChunkKey(c1.chunkX, c1.chunkZ);
-        final long coord2 = CoordinateUtils.getChunkKey(c2.chunkX, c2.chunkZ);
+    private ChunkHolderManager.HolderManagerRegionData getCurrentRegionData() {
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
 
-        if (coord1 == coord2) {
-            throw new IllegalStateException("Duplicate chunkholder in auto save queue");
+        if (region == null) {
+            return null;
         }
 
-        return Long.compare(coord1, coord2);
-    });
+        if (this.world != null && this.world != region.getData().world) {
+            throw new IllegalStateException("World check failed: expected world: " + this.world.getWorld().getKey() + ", region world: " + region.getData().world.getWorld().getKey());
+        }
+
+        return region.getData().getHolderManagerRegionData();
+    }
+    // Folia end - region threading
+
 
     public ChunkHolderManager(final ServerLevel world, final ChunkTaskScheduler taskScheduler) {
         this.world = world;
@@ -167,8 +231,13 @@ public final class ChunkHolderManager {
     }
 
     public void close(final boolean save, final boolean halt) {
+        // Folia start - region threading
+        this.close(save, halt, true, true, true);
+    }
+    public void close(final boolean save, final boolean halt, final boolean first, final boolean last, final boolean checkRegions) {
+        // Folia end - region threading
         TickThread.ensureTickThread("Closing world off-main");
-        if (halt) {
+        if (first && halt) { // Folia - region threading
             LOGGER.info("Waiting 60s for chunk system to halt for world '" + this.world.getWorld().getName() + "'");
             if (!this.taskScheduler.halt(true, TimeUnit.SECONDS.toNanos(60L))) {
                 LOGGER.warn("Failed to halt world generation/loading tasks for world '" + this.world.getWorld().getName() + "'");
@@ -178,9 +247,10 @@ public final class ChunkHolderManager {
         }
 
         if (save) {
-            this.saveAllChunks(true, true, true);
+            this.saveAllChunksRegionised(true, true, true, first, last, checkRegions); // Folia - region threading
         }
 
+        if (last) { // Folia - region threading
         if (this.world.chunkDataControllerNew.hasTasks() || this.world.entityDataControllerNew.hasTasks() || this.world.poiDataControllerNew.hasTasks()) {
             RegionFileIOThread.flush();
         }
@@ -201,27 +271,34 @@ public final class ChunkHolderManager {
         } catch (final IOException ex) {
             LOGGER.error("Failed to close poi regionfile cache for world '" + this.world.getWorld().getName() + "'", ex);
         }
+        } // Folia - region threading
     }
 
     void ensureInAutosave(final NewChunkHolder holder) {
-        if (!this.autoSaveQueue.contains(holder)) {
-            holder.lastAutoSave = MinecraftServer.currentTick;
-            this.autoSaveQueue.add(holder);
+        // Folia start - region threading
+        final HolderManagerRegionData regionData = this.getCurrentRegionData();
+        if (!regionData.autoSaveQueue.contains(holder)) {
+            holder.lastAutoSave = RegionizedServer.getCurrentTick();
+            // Folia end - region threading
+            regionData.autoSaveQueue.add(holder);
         }
     }
 
     public void autoSave() {
         final List<NewChunkHolder> reschedule = new ArrayList<>();
-        final long currentTick = MinecraftServer.currentTickLong;
+        final long currentTick = RegionizedServer.getCurrentTick(); // Folia - region threading
         final long maxSaveTime = currentTick - this.world.paperConfig().chunks.autoSaveInterval.value();
-        for (int autoSaved = 0; autoSaved < this.world.paperConfig().chunks.maxAutoSaveChunksPerTick && !this.autoSaveQueue.isEmpty();) {
-            final NewChunkHolder holder = this.autoSaveQueue.first();
+        // Folia start - region threading
+        final HolderManagerRegionData regionData = this.getCurrentRegionData();
+        for (int autoSaved = 0; autoSaved < this.world.paperConfig().chunks.maxAutoSaveChunksPerTick && !regionData.autoSaveQueue.isEmpty();) {
+            // Folia end - region threading
+            final NewChunkHolder holder = regionData.autoSaveQueue.first();
 
             if (holder.lastAutoSave > maxSaveTime) {
                 break;
             }
 
-            this.autoSaveQueue.remove(holder);
+            regionData.autoSaveQueue.remove(holder); // Folia - region threading
 
             holder.lastAutoSave = currentTick;
             if (holder.save(false, false) != null) {
@@ -235,15 +312,38 @@ public final class ChunkHolderManager {
 
         for (final NewChunkHolder holder : reschedule) {
             if (holder.getChunkStatus().isOrAfter(FullChunkStatus.FULL)) {
-                this.autoSaveQueue.add(holder);
+                regionData.autoSaveQueue.add(holder); // Folia start - region threading
             }
         }
     }
 
     public void saveAllChunks(final boolean flush, final boolean shutdown, final boolean logProgress) {
-        final List<NewChunkHolder> holders = this.getChunkHolders();
+        // Folia start - region threading
+        this.saveAllChunksRegionised(flush, shutdown, logProgress, true, true, true);
+    }
+    public void saveAllChunksRegionised(final boolean flush, final boolean shutdown, final boolean logProgress, final boolean first, final boolean last, final boolean checkRegion) {
+        final List<NewChunkHolder> holders = new java.util.ArrayList<>(this.chunkHolders.size() / 10);
+        // we could iterate through all chunk holders with thread checks, however for many regions the iteration cost alone
+        // will multiply. to avoid this, we can simply iterate through all owned sections
+        final int regionShift = this.world.getRegionChunkShift();
+        for (final LongIterator iterator = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegion().getOwnedSectionsUnsynchronised(); iterator.hasNext();) {
+            final long sectionKey = iterator.nextLong();
+            final int width = 1 << regionShift;
+            final int offsetX = CoordinateUtils.getChunkX(sectionKey) << regionShift;
+            final int offsetZ = CoordinateUtils.getChunkZ(sectionKey) << regionShift;
+
+            for (int dz = 0; dz < width; ++dz) {
+                for (int dx = 0; dx < width; ++dx) {
+                    final NewChunkHolder holder = this.getChunkHolder(offsetX | dx, offsetZ | dz);
+                    if (holder != null) {
+                        holders.add(holder);
+                    }
+                }
+            }
+        }
+        // Folia end - region threading
 
-        if (logProgress) {
+        if (first && logProgress) { // Folia - region threading
             LOGGER.info("Saving all chunkholders for world '" + this.world.getWorld().getName() + "'");
         }
 
@@ -251,7 +351,7 @@ public final class ChunkHolderManager {
 
         int saved = 0;
 
-        long start = System.nanoTime();
+        final long start = System.nanoTime();
         long lastLog = start;
         boolean needsFlush = false;
         final int flushInterval = 50;
@@ -262,6 +362,12 @@ public final class ChunkHolderManager {
 
         for (int i = 0, len = holders.size(); i < len; ++i) {
             final NewChunkHolder holder = holders.get(i);
+            // Folia start - region threading
+            if (!checkRegion && !TickThread.isTickThreadFor(this.world, holder.chunkX, holder.chunkZ)) {
+                // skip holders that would fail the thread check
+                continue;
+            }
+            // Folia end - region threading
             try {
                 final NewChunkHolder.SaveStat saveStat = holder.save(shutdown, false);
                 if (saveStat != null) {
@@ -294,7 +400,7 @@ public final class ChunkHolderManager {
                 }
             }
         }
-        if (flush) {
+        if (last && flush) { // Folia - region threading
             RegionFileIOThread.flush();
             if (this.world.paperConfig().chunks.flushRegionsOnSave) {
                 try {
@@ -707,6 +813,13 @@ public final class ChunkHolderManager {
     }
 
     public void tick() {
+        // Folia start - region threading
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            throw new IllegalStateException("Not running tick() while on a region");
+        }
+        // Folia end - region threading
         final int sectionShift = this.world.getRegionChunkShift();
 
         final Predicate<Ticket<?>> expireNow = (final Ticket<?> ticket) -> {
@@ -716,12 +829,12 @@ public final class ChunkHolderManager {
             return --ticket.removeDelay <= 0L;
         };
 
-        for (final Iterator<RegionFileIOThread.ChunkCoordinate> iterator = this.sectionToChunkToExpireCount.keySet().iterator(); iterator.hasNext();) {
-            final RegionFileIOThread.ChunkCoordinate section = iterator.next();
-            final long sectionKey = section.key;
-
+        // Folia start - region threading
+        for (final LongIterator iterator = region.getOwnedSectionsUnsynchronised(); iterator.hasNext();) {
+            final long sectionKey = iterator.nextLong();
+            final RegionFileIOThread.ChunkCoordinate section = new RegionFileIOThread.ChunkCoordinate(sectionKey);
             if (!this.sectionToChunkToExpireCount.containsKey(section)) {
-                // removed concurrently
+                // Folia end - region threading
                 continue;
             }
 
@@ -1024,19 +1137,51 @@ public final class ChunkHolderManager {
         if (changedFullStatus.isEmpty()) {
             return;
         }
-        if (!TickThread.isTickThread()) {
-            this.taskScheduler.scheduleChunkTask(() -> {
-                final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = ChunkHolderManager.this.pendingFullLoadUpdate;
-                for (int i = 0, len = changedFullStatus.size(); i < len; ++i) {
-                    pendingFullLoadUpdate.add(changedFullStatus.get(i));
-                }
 
-                ChunkHolderManager.this.processPendingFullUpdate();
-            }, PrioritisedExecutor.Priority.HIGHEST);
-        } else {
-            final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = this.pendingFullLoadUpdate;
-            for (int i = 0, len = changedFullStatus.size(); i < len; ++i) {
-                pendingFullLoadUpdate.add(changedFullStatus.get(i));
+        // Folia start - region threading
+        final Long2ObjectOpenHashMap<List<NewChunkHolder>> sectionToUpdates = new Long2ObjectOpenHashMap<>();
+        final List<NewChunkHolder> thisRegionHolders = new ArrayList<>();
+
+        final int regionShift = this.world.getRegionChunkShift();
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> thisRegion
+            = TickRegionScheduler.getCurrentRegion();
+
+        for (final NewChunkHolder holder : changedFullStatus) {
+            final int regionX = holder.chunkX >> regionShift;
+            final int regionZ = holder.chunkZ >> regionShift;
+            final long holderSectionKey = CoordinateUtils.getChunkKey(regionX, regionZ);
+
+            // region may be null
+            if (thisRegion != null && this.world.regioniser.getRegionAtUnsynchronised(holder.chunkX, holder.chunkZ) == thisRegion) {
+                thisRegionHolders.add(holder);
+            } else {
+                sectionToUpdates.computeIfAbsent(holderSectionKey, (final long keyInMap) -> {
+                    return new ArrayList<>();
+                }).add(holder);
+            }
+        }
+        // Folia end - region threading
+
+        // Folia start - region threading
+        if (!thisRegionHolders.isEmpty()) {
+            thisRegion.getData().getHolderManagerRegionData().pendingFullLoadUpdate.addAll(thisRegionHolders);
+        }
+
+        if (!sectionToUpdates.isEmpty()) {
+            for (final Iterator<Long2ObjectMap.Entry<List<NewChunkHolder>>> iterator = sectionToUpdates.long2ObjectEntrySet().fastIterator();
+                iterator.hasNext();) {
+                final Long2ObjectMap.Entry<List<NewChunkHolder>> entry = iterator.next();
+                final long sectionKey = entry.getLongKey();
+
+                final int chunkX = CoordinateUtils.getChunkX(sectionKey) << regionShift;
+                final int chunkZ = CoordinateUtils.getChunkZ(sectionKey) << regionShift;
+
+                final List<NewChunkHolder> regionHolders = entry.getValue();
+                this.taskScheduler.scheduleChunkTaskEventually(chunkX, chunkZ, () -> { // Folia - region threading
+                    ChunkHolderManager.this.getCurrentRegionData().pendingFullLoadUpdate.addAll(regionHolders);
+                    ChunkHolderManager.this.processPendingFullUpdate();
+                }, PrioritisedExecutor.Priority.HIGHEST);
+                // Folia end - region threading
             }
         }
     }
@@ -1044,8 +1189,9 @@ public final class ChunkHolderManager {
     private void removeChunkHolder(final NewChunkHolder holder) {
         holder.killed = true;
         holder.vanillaChunkHolder.onChunkRemove();
-        this.autoSaveQueue.remove(holder);
+        // Folia - region threading
         ChunkSystem.onChunkHolderDelete(this.world, holder.vanillaChunkHolder);
+        this.getCurrentRegionData().autoSaveQueue.remove(holder); // Folia - region threading
         synchronized (this.chunkHolders) {
             this.chunkHolders.remove(CoordinateUtils.getChunkKey(holder.chunkX, holder.chunkZ));
         }
@@ -1059,7 +1205,7 @@ public final class ChunkHolderManager {
             throw new IllegalStateException("Cannot unload chunks recursively");
         }
         final int sectionShift = this.unloadQueue.coordinateShift; // sectionShift <= lock shift
-        final List<ChunkQueue.SectionToUnload> unloadSectionsForRegion = this.unloadQueue.retrieveForAllRegions();
+        final List<ChunkQueue.SectionToUnload> unloadSectionsForRegion = this.unloadQueue.retrieveForCurrentRegion(); // Folia - threaded regions
         int unloadCountTentative = 0;
         for (final ChunkQueue.SectionToUnload sectionRef : unloadSectionsForRegion) {
             final ChunkQueue.UnloadSection section
@@ -1372,7 +1518,13 @@ public final class ChunkHolderManager {
 
     // only call on tick thread
     protected final boolean processPendingFullUpdate() {
-        final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = this.pendingFullLoadUpdate;
+        // Folia start - region threading
+        final HolderManagerRegionData data = this.getCurrentRegionData();
+        if (data == null) {
+            return false;
+        }
+        final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = data.pendingFullLoadUpdate;
+        // Folia end - region threading
 
         boolean ret = false;
 
@@ -1383,9 +1535,7 @@ public final class ChunkHolderManager {
             ret |= holder.handleFullStatusChange(changedFullStatus);
 
             if (!changedFullStatus.isEmpty()) {
-                for (int i = 0, len = changedFullStatus.size(); i < len; ++i) {
-                    pendingFullLoadUpdate.add(changedFullStatus.get(i));
-                }
+                this.addChangedStatuses(changedFullStatus); // Folia - region threading
                 changedFullStatus.clear();
             }
         }
@@ -1399,7 +1549,7 @@ public final class ChunkHolderManager {
 
     private JsonObject getDebugJsonNoLock() {
         final JsonObject ret = new JsonObject();
-        ret.addProperty("current_tick", Long.valueOf(this.currentTick));
+        // Folia - region threading - move down
 
         final JsonArray unloadQueue = new JsonArray();
         ret.add("unload_queue", unloadQueue);
diff --git a/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkQueue.java b/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkQueue.java
index 4cc1b3ba6d093a9683dbd8b7fe76106ae391e019..47bbd5de5849bef5392e3783322a19de5b351beb 100644
--- a/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkQueue.java
+++ b/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkQueue.java
@@ -1,5 +1,8 @@
 package io.papermc.paper.chunk.system.scheduling;
 
+import io.papermc.paper.threadedregions.ThreadedRegionizer;
+import io.papermc.paper.threadedregions.TickRegionScheduler;
+import io.papermc.paper.threadedregions.TickRegions;
 import it.unimi.dsi.fastutil.HashCommon;
 import it.unimi.dsi.fastutil.longs.LongLinkedOpenHashSet;
 import java.util.ArrayList;
@@ -45,6 +48,39 @@ public final class ChunkQueue {
         return ret;
     }
 
+    // Folia start - threaded regions
+    public List<SectionToUnload> retrieveForCurrentRegion() {
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        final ThreadedRegionizer<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regionizer = region.regioniser;
+        final int shift = this.coordinateShift;
+
+        final List<SectionToUnload> ret = new ArrayList<>();
+
+        for (final Map.Entry<Coordinate, UnloadSection> entry : this.unloadSections.entrySet()) {
+            final Coordinate coord = entry.getKey();
+            final long key = coord.key;
+            final UnloadSection section = entry.getValue();
+            final int sectionX = Coordinate.x(key);
+            final int sectionZ = Coordinate.z(key);
+            final int chunkX = sectionX << shift;
+            final int chunkZ = sectionZ << shift;
+
+            if (regionizer.getRegionAtUnsynchronised(chunkX, chunkZ) != region) {
+                continue;
+            }
+
+            ret.add(new SectionToUnload(sectionX, sectionZ, coord, section.order, section.chunks.size()));
+        }
+
+        ret.sort((final SectionToUnload s1, final SectionToUnload s2) -> {
+            return Long.compare(s1.order, s2.order);
+        });
+
+        return ret;
+    }
+    // Folia end - threaded regions
+
     public UnloadSection getSectionUnsynchronized(final int sectionX, final int sectionZ) {
         final Coordinate coordinate = new Coordinate(Coordinate.key(sectionX, sectionZ));
         return this.unloadSections.get(coordinate);
diff --git a/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkTaskScheduler.java b/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkTaskScheduler.java
index 17ce14f2dcbf900890efbc2351782bc6f8867068..92f37abe3eb7ad85fd60d3c80acf77dc575b26ea 100644
--- a/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkTaskScheduler.java
+++ b/src/main/java/io/papermc/paper/chunk/system/scheduling/ChunkTaskScheduler.java
@@ -115,7 +115,7 @@ public final class ChunkTaskScheduler {
     private final PrioritisedThreadPool.PrioritisedPoolExecutor radiusAwareGenExecutor;
     public final PrioritisedThreadPool.PrioritisedPoolExecutor loadExecutor;
 
-    private final PrioritisedThreadedTaskQueue mainThreadExecutor = new PrioritisedThreadedTaskQueue();
+    // Folia - regionised ticking
 
     public final ChunkHolderManager chunkHolderManager;
 
@@ -303,14 +303,13 @@ public final class ChunkTaskScheduler {
         };
 
         // this may not be good enough, specifically thanks to stupid ass plugins swallowing exceptions
-        this.scheduleChunkTask(chunkX, chunkZ, crash, PrioritisedExecutor.Priority.BLOCKING);
+        this.scheduleChunkTaskEventually(chunkX, chunkZ, crash, PrioritisedExecutor.Priority.BLOCKING); // Folia - region threading
         // so, make the main thread pick it up
         MinecraftServer.chunkSystemCrash = new RuntimeException("Chunk system crash propagated from unrecoverableChunkSystemFailure", reportedException);
     }
 
     public boolean executeMainThreadTask() {
-        TickThread.ensureTickThread("Cannot execute main thread task off-main");
-        return this.mainThreadExecutor.executeTask();
+        throw new UnsupportedOperationException("Use regionised ticking hooks"); // Folia - regionised ticking
     }
 
     public void raisePriority(final int x, final int z, final PrioritisedExecutor.Priority priority) {
@@ -330,7 +329,7 @@ public final class ChunkTaskScheduler {
     public void scheduleTickingState(final int chunkX, final int chunkZ, final FullChunkStatus toStatus,
                                      final boolean addTicket, final PrioritisedExecutor.Priority priority,
                                      final Consumer<LevelChunk> onComplete) {
-        if (!TickThread.isTickThread()) {
+        if (!TickThread.isTickThreadFor(this.world, chunkX, chunkZ)) {
             this.scheduleChunkTask(chunkX, chunkZ, () -> {
                 ChunkTaskScheduler.this.scheduleTickingState(chunkX, chunkZ, toStatus, addTicket, priority, onComplete);
             }, priority);
@@ -486,7 +485,7 @@ public final class ChunkTaskScheduler {
 
     public void scheduleChunkLoad(final int chunkX, final int chunkZ, final ChunkStatus toStatus, final boolean addTicket,
                                   final PrioritisedExecutor.Priority priority, final Consumer<ChunkAccess> onComplete) {
-        if (!TickThread.isTickThread()) {
+        if (!TickThread.isTickThreadFor(this.world, chunkX, chunkZ)) {
             this.scheduleChunkTask(chunkX, chunkZ, () -> {
                 ChunkTaskScheduler.this.scheduleChunkLoad(chunkX, chunkZ, toStatus, addTicket, priority, onComplete);
             }, priority);
@@ -514,7 +513,7 @@ public final class ChunkTaskScheduler {
             this.chunkHolderManager.processTicketUpdates();
         }
 
-        final Consumer<ChunkAccess> loadCallback = (final ChunkAccess chunk) -> {
+        final Consumer<ChunkAccess> loadCallback = onComplete == null && !addTicket ? null : (final ChunkAccess chunk) -> {
             try {
                 if (onComplete != null) {
                     onComplete.accept(chunk);
@@ -554,7 +553,9 @@ public final class ChunkTaskScheduler {
                         if (!chunkHolder.upgradeGenTarget(toStatus)) {
                             this.schedule(chunkX, chunkZ, toStatus, chunkHolder, tasks);
                         }
-                        chunkHolder.addStatusConsumer(toStatus, loadCallback);
+                        if (loadCallback != null) {
+                            chunkHolder.addStatusConsumer(toStatus, loadCallback);
+                        }
                     }
                 }
             } finally {
@@ -568,7 +569,7 @@ public final class ChunkTaskScheduler {
             tasks.get(i).schedule();
         }
 
-        if (!scheduled) {
+        if (loadCallback != null && !scheduled) {
             // couldn't schedule
             try {
                 loadCallback.accept(chunk);
@@ -757,7 +758,7 @@ public final class ChunkTaskScheduler {
      */
     @Deprecated
     public PrioritisedExecutor.PrioritisedTask scheduleChunkTask(final Runnable run) {
-        return this.scheduleChunkTask(run, PrioritisedExecutor.Priority.NORMAL);
+        throw new UnsupportedOperationException(); // Folia - regionised ticking
     }
 
     /**
@@ -765,7 +766,7 @@ public final class ChunkTaskScheduler {
      */
     @Deprecated
     public PrioritisedExecutor.PrioritisedTask scheduleChunkTask(final Runnable run, final PrioritisedExecutor.Priority priority) {
-        return this.mainThreadExecutor.queueRunnable(run, priority);
+        throw new UnsupportedOperationException(); // Folia - regionised ticking
     }
 
     public PrioritisedExecutor.PrioritisedTask createChunkTask(final int chunkX, final int chunkZ, final Runnable run) {
@@ -774,28 +775,33 @@ public final class ChunkTaskScheduler {
 
     public PrioritisedExecutor.PrioritisedTask createChunkTask(final int chunkX, final int chunkZ, final Runnable run,
                                                                final PrioritisedExecutor.Priority priority) {
-        return this.mainThreadExecutor.createTask(run, priority);
+        return MinecraftServer.getServer().regionizedServer.taskQueue.createChunkTask(this.world, chunkX, chunkZ, run, priority); // Folia - regionised ticking
     }
 
     public PrioritisedExecutor.PrioritisedTask scheduleChunkTask(final int chunkX, final int chunkZ, final Runnable run) {
-        return this.mainThreadExecutor.queueRunnable(run);
+        return this.scheduleChunkTask(chunkX, chunkZ, run, PrioritisedExecutor.Priority.NORMAL); // TODO rebase into chunk system patch
     }
 
     public PrioritisedExecutor.PrioritisedTask scheduleChunkTask(final int chunkX, final int chunkZ, final Runnable run,
                                                                  final PrioritisedExecutor.Priority priority) {
-        return this.mainThreadExecutor.queueRunnable(run, priority);
+        return MinecraftServer.getServer().regionizedServer.taskQueue.queueChunkTask(this.world, chunkX, chunkZ, run, priority); // Folia - regionised ticking
+    }
+
+    // Folia start - region threading
+    // this function is guaranteed to never touch the ticket lock or schedule lock
+    // yes, this IS a hack so that we can avoid deadlock due to region threading introducing the
+    // ticket lock in the schedule logic
+    public PrioritisedExecutor.PrioritisedTask scheduleChunkTaskEventually(final int chunkX, final int chunkZ, final Runnable run,
+                                                                           final PrioritisedExecutor.Priority priority) {
+        final PrioritisedExecutor.PrioritisedTask ret = this.createChunkTask(chunkX, chunkZ, run, priority);
+        this.world.taskQueueRegionData.pushGlobalChunkTask(() -> {
+            MinecraftServer.getServer().regionizedServer.taskQueue.queueChunkTask(ChunkTaskScheduler.this.world, chunkX, chunkZ, run, priority);
+        });
+        return ret;
     }
+    // Folia end - region threading
 
-    public void executeTasksUntil(final BooleanSupplier exit) {
-        if (Bukkit.isPrimaryThread()) {
-            this.mainThreadExecutor.executeConditionally(exit);
-        } else {
-            long counter = 1L;
-            while (!exit.getAsBoolean()) {
-                counter = ConcurrentUtil.linearLongBackoff(counter, 100_000L, 5_000_000L); // 100us, 5ms
-            }
-        }
-    }
+    // Folia - regionised ticking
 
     public boolean halt(final boolean sync, final long maxWaitNS) {
         this.radiusAwareGenExecutor.halt();
@@ -803,6 +809,7 @@ public final class ChunkTaskScheduler {
         this.loadExecutor.halt();
         final long time = System.nanoTime();
         if (sync) {
+            // start at 10 * 0.5ms -> 5ms
             for (long failures = 9L;; failures = ConcurrentUtil.linearLongBackoff(failures, 500_000L, 50_000_000L)) {
                 if (
                         !this.radiusAwareGenExecutor.isActive() &&
diff --git a/src/main/java/io/papermc/paper/chunk/system/scheduling/NewChunkHolder.java b/src/main/java/io/papermc/paper/chunk/system/scheduling/NewChunkHolder.java
index b66a7d4aab887309579154815a0d4abf9de506b0..08075b8895f816420c2a940bf551dfada3c0cd9e 100644
--- a/src/main/java/io/papermc/paper/chunk/system/scheduling/NewChunkHolder.java
+++ b/src/main/java/io/papermc/paper/chunk/system/scheduling/NewChunkHolder.java
@@ -726,7 +726,7 @@ public final class NewChunkHolder {
     boolean killed;
 
     // must hold scheduling lock
-    private void checkUnload() {
+    void checkUnload() { // Folia - region threading
         if (this.killed) {
             return;
         }
@@ -1440,7 +1440,7 @@ public final class NewChunkHolder {
         }
 
         // must be scheduled to main, we do not trust the callback to not do anything stupid
-        this.scheduler.scheduleChunkTask(this.chunkX, this.chunkZ, () -> {
+        this.scheduler.scheduleChunkTaskEventually(this.chunkX, this.chunkZ, () -> { // Folia - region threading
             for (final Consumer<ChunkAccess> consumer : consumers) {
                 try {
                     consumer.accept(chunk);
@@ -1483,7 +1483,7 @@ public final class NewChunkHolder {
         }
 
         // must be scheduled to main, we do not trust the callback to not do anything stupid
-        this.scheduler.scheduleChunkTask(this.chunkX, this.chunkZ, () -> {
+        this.scheduler.scheduleChunkTaskEventually(this.chunkX, this.chunkZ, () -> { // Folia - region threading
             for (final Consumer<LevelChunk> consumer : consumers) {
                 try {
                     consumer.accept(chunk);
@@ -1744,7 +1744,7 @@ public final class NewChunkHolder {
         return this.entityChunk;
     }
 
-    public long lastAutoSave;
+    public long lastAutoSave; // Folia - region threaded - change to relative delay
 
     public static final record SaveStat(boolean savedChunk, boolean savedEntityChunk, boolean savedPoiChunk) {}
 
@@ -1894,7 +1894,7 @@ public final class NewChunkHolder {
         } catch (final ThreadDeath death) {
             throw death;
         } catch (final Throwable thr) {
-            LOGGER.error("Failed to save chunk data (" + this.chunkX + "," + this.chunkZ + ") in world '" + this.world.getWorld().getName() + "'");
+            LOGGER.error("Failed to save chunk data (" + this.chunkX + "," + this.chunkZ + ") in world '" + this.world.getWorld().getName() + "'", thr); // TODO rebase
             if (unloading && !completing) {
                 this.completeAsyncChunkDataSave(null);
             }
@@ -1942,7 +1942,7 @@ public final class NewChunkHolder {
         } catch (final ThreadDeath death) {
             throw death;
         } catch (final Throwable thr) {
-            LOGGER.error("Failed to save entity data (" + this.chunkX + "," + this.chunkZ + ") in world '" + this.world.getWorld().getName() + "'");
+            LOGGER.error("Failed to save entity data (" + this.chunkX + "," + this.chunkZ + ") in world '" + this.world.getWorld().getName() + "'", thr); // TODO rebase
         }
 
         return true;
@@ -1968,7 +1968,7 @@ public final class NewChunkHolder {
         } catch (final ThreadDeath death) {
             throw death;
         } catch (final Throwable thr) {
-            LOGGER.error("Failed to save poi data (" + this.chunkX + "," + this.chunkZ + ") in world '" + this.world.getWorld().getName() + "'");
+            LOGGER.error("Failed to save poi data (" + this.chunkX + "," + this.chunkZ + ") in world '" + this.world.getWorld().getName() + "'", thr); // TODO rebase
         }
 
         return true;
diff --git a/src/main/java/io/papermc/paper/command/PaperCommands.java b/src/main/java/io/papermc/paper/command/PaperCommands.java
index 7b58b2d6297800c2dcdbf7539e5ab8e7703f39f1..a587d83b78af4efc484f939529acf70834f60d7e 100644
--- a/src/main/java/io/papermc/paper/command/PaperCommands.java
+++ b/src/main/java/io/papermc/paper/command/PaperCommands.java
@@ -19,6 +19,7 @@ public final class PaperCommands {
         COMMANDS.put("paper", new PaperCommand("paper"));
         COMMANDS.put("callback", new CallbackCommand("callback"));
         COMMANDS.put("mspt", new MSPTCommand("mspt"));
+        COMMANDS.put("tps", new io.papermc.paper.threadedregions.commands.CommandServerHealth()); // Folia - region threading
     }
 
     public static void registerCommands(final MinecraftServer server) {
diff --git a/src/main/java/io/papermc/paper/command/subcommands/EntityCommand.java b/src/main/java/io/papermc/paper/command/subcommands/EntityCommand.java
index 5e5a018433414af76eaa1e781f61612ddc305b07..2ad2e5d5cd78f67d5d4c0a5b337c521bfca39aa8 100644
--- a/src/main/java/io/papermc/paper/command/subcommands/EntityCommand.java
+++ b/src/main/java/io/papermc/paper/command/subcommands/EntityCommand.java
@@ -129,7 +129,7 @@ public final class EntityCommand implements PaperSubcommand {
                         final int z = (e.getKey().z << 4) + 8;
                         final Component message = text("  " + e.getValue() + ": " + e.getKey().x + ", " + e.getKey().z + (chunkProviderServer.isPositionTicking(e.getKey().toLong()) ? " (Ticking)" : " (Non-Ticking)"))
                             .hoverEvent(HoverEvent.showText(text("Click to teleport to chunk", GREEN)))
-                            .clickEvent(ClickEvent.clickEvent(ClickEvent.Action.RUN_COMMAND, "/minecraft:execute as @s in " + world.getWorld().getKey() + " run tp " + x + " " + (world.getWorld().getHighestBlockYAt(x, z, HeightMap.MOTION_BLOCKING) + 1) + " " + z));
+                            .clickEvent(ClickEvent.clickEvent(ClickEvent.Action.RUN_COMMAND, "/minecraft:execute as @s in " + world.getWorld().getKey() + " run tp " + x + " " + (128) + " " + z)); // Folia - region threading - avoid sync load here
                         sender.sendMessage(message);
                     });
             } else {
diff --git a/src/main/java/io/papermc/paper/command/subcommands/HeapDumpCommand.java b/src/main/java/io/papermc/paper/command/subcommands/HeapDumpCommand.java
index cd2e4d792e972b8bf1e07b8961594a670ae949cf..3ab8dbf2768a4ef8fb53af6f5431f7f6afe6d168 100644
--- a/src/main/java/io/papermc/paper/command/subcommands/HeapDumpCommand.java
+++ b/src/main/java/io/papermc/paper/command/subcommands/HeapDumpCommand.java
@@ -18,7 +18,9 @@ import static net.kyori.adventure.text.format.NamedTextColor.YELLOW;
 public final class HeapDumpCommand implements PaperSubcommand {
     @Override
     public boolean execute(final CommandSender sender, final String subCommand, final String[] args) {
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         this.dumpHeap(sender);
+        }); // Folia - region threading
         return true;
     }
 
diff --git a/src/main/java/io/papermc/paper/command/subcommands/ReloadCommand.java b/src/main/java/io/papermc/paper/command/subcommands/ReloadCommand.java
index bd68139ae635f2ad7ec8e7a21e0056a139c4c62e..48a43341b17247355a531164019d5cc9c5555f26 100644
--- a/src/main/java/io/papermc/paper/command/subcommands/ReloadCommand.java
+++ b/src/main/java/io/papermc/paper/command/subcommands/ReloadCommand.java
@@ -16,7 +16,9 @@ import static net.kyori.adventure.text.format.NamedTextColor.RED;
 public final class ReloadCommand implements PaperSubcommand {
     @Override
     public boolean execute(final CommandSender sender, final String subCommand, final String[] args) {
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         this.doReload(sender);
+        }); // Folia - region threading
         return true;
     }
 
diff --git a/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java b/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
index 30fe1c0645a07d663b08c0f988a1ab3a750bf7c4..e45e2303ac69ce3a158bebb52bc8cbd96ceb3f71 100644
--- a/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
+++ b/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
@@ -346,4 +346,18 @@ public class GlobalConfiguration extends ConfigurationPart {
         public boolean disableChorusPlantUpdates = false;
         public boolean disableMushroomBlockUpdates = false;
     }
+
+    // Folia start - threaded regions
+    public ThreadedRegions threadedRegions;
+    public class ThreadedRegions extends ConfigurationPart {
+
+        public int threads = -1;
+        public int gridExponent = 2;
+
+        @PostProcess
+        public void postProcess() {
+            io.papermc.paper.threadedregions.TickRegions.init(this);
+        }
+    }
+    // Folia end - threaded regions
 }
diff --git a/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java b/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java
index d3fdf62912d190f8b468b77230a927023c361074..17b538ee7591a75a5fc7e797c73e7730652fed69 100644
--- a/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java
+++ b/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java
@@ -475,6 +475,14 @@ public class WorldConfiguration extends ConfigurationPart {
     public Chunks chunks;
 
     public class Chunks extends ConfigurationPart {
+
+        // Folia start - region threading - force prevent moving into unloaded chunks
+        @PostProcess
+        public void postProcess() {
+            this.preventMovingIntoUnloadedChunks = true;
+        }
+        // Folia end - region threading - force prevent moving into unloaded chunks
+
         public AutosavePeriod autoSaveInterval = AutosavePeriod.def();
         public int maxAutoSaveChunksPerTick = 24;
         public int fixedChunkInhabitedTime = -1;
diff --git a/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java b/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java
index eedbf46e04b5ae420f9bedcbc2bbb10643ba7e22..afc9c6e6e8bc4a4706474134dae5484459531226 100644
--- a/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java
+++ b/src/main/java/io/papermc/paper/plugin/manager/PaperPluginInstanceManager.java
@@ -242,12 +242,7 @@ class PaperPluginInstanceManager {
                 + pluginName + " (Is it up to date?)", ex, plugin); // Paper
         }
 
-        try {
-            this.server.getScheduler().cancelTasks(plugin);
-        } catch (Throwable ex) {
-            this.handlePluginException("Error occurred (in the plugin loader) while cancelling tasks for "
-                + pluginName + " (Is it up to date?)", ex, plugin); // Paper
-        }
+        // Folia - region threading
 
         // Paper start - Folia schedulers
         try {
diff --git a/src/main/java/io/papermc/paper/threadedregions/RegionShutdownThread.java b/src/main/java/io/papermc/paper/threadedregions/RegionShutdownThread.java
new file mode 100644
index 0000000000000000000000000000000000000000..3f3fd8b1881106f893ffb677272e50d77cbb6626
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionShutdownThread.java
@@ -0,0 +1,175 @@
+package io.papermc.paper.threadedregions;
+
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.util.TickThread;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.ChunkPos;
+import org.slf4j.Logger;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+public final class RegionShutdownThread extends TickThread {
+
+    private static final Logger LOGGER = LogUtils.getClassLogger();
+
+    ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> shuttingDown;
+
+    public RegionShutdownThread(final String name) {
+        super(name);
+        this.setUncaughtExceptionHandler((thread, thr) -> {
+            LOGGER.error("Error shutting down server", thr);
+        });
+    }
+
+    static ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> getRegion() {
+        final Thread currentThread = Thread.currentThread();
+        if (currentThread instanceof RegionShutdownThread shutdownThread) {
+            return shutdownThread.shuttingDown;
+        }
+        return null;
+    }
+
+
+    static RegionizedWorldData getWorldData() {
+        final Thread currentThread = Thread.currentThread();
+        if (currentThread instanceof RegionShutdownThread shutdownThread) {
+            // no fast path for shutting down
+            if (shutdownThread.shuttingDown != null) {
+                return shutdownThread.shuttingDown.getData().world.worldRegionData.get();
+            }
+        }
+        return null;
+    }
+
+    // The region shutdown thread bypasses all tick thread checks, which will allow us to execute global saves
+    // it will not however let us perform arbitrary sync loads, arbitrary world state lookups simply because
+    // the data required to do that is regionised, and we can only access it when we OWN the region, and we do not.
+    // Thus, the only operation that the shutdown thread will perform
+
+    private void saveLevelData(final ServerLevel world) {
+        try {
+            world.saveLevelData(false);
+        } catch (final Throwable thr) {
+            LOGGER.error("Failed to save level data for " + world.getWorld().getName(), thr);
+        }
+    }
+
+    private void finishTeleportations(final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region,
+                                      final ServerLevel world) {
+        try {
+            this.shuttingDown = region;
+            final List<ServerLevel.PendingTeleport> pendingTeleports = world.removeAllRegionTeleports();
+            if (pendingTeleports.isEmpty()) {
+                return;
+            }
+            final ChunkPos center = region.getCenterChunk();
+            LOGGER.info("Completing " + pendingTeleports.size() + " pending teleports in region around chunk " + center + " in world '" + region.regioniser.world.getWorld().getName() + "'");
+            for (final ServerLevel.PendingTeleport pendingTeleport : pendingTeleports) {
+                LOGGER.info("Completing teleportation to target position " + pendingTeleport.to());
+
+                // first, add entities to entity chunk so that they will be saved
+                for (final Entity.EntityTreeNode node : pendingTeleport.rootVehicle().getFullTree()) {
+                    // assume that world and position are set to destination here
+                    node.root.setLevel(world); // in case the pending teleport is from a portal before it finds the exact destination
+                    world.getEntityLookup().addEntityForShutdownTeleportComplete(node.root);
+                }
+
+                // then, rebuild the passenger tree so that when saving only the root vehicle will be written - and if
+                // there are any player passengers, that the later player saving will save the tree
+                pendingTeleport.rootVehicle().restore();
+
+                // now we are finished
+                LOGGER.info("Completed teleportation to target position " + pendingTeleport.to());
+            }
+        } catch (final Throwable thr) {
+            LOGGER.error("Failed to complete pending teleports", thr);
+        } finally {
+            this.shuttingDown = null;
+        }
+    }
+
+    private void saveRegionChunks(final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region,
+                                  final boolean last) {
+        ChunkPos center = null;
+        try {
+            this.shuttingDown = region;
+            center = region.getCenterChunk();
+            LOGGER.info("Saving chunks around region around chunk " + center + " in world '" + region.regioniser.world.getWorld().getName() + "'");
+            region.regioniser.world.chunkTaskScheduler.chunkHolderManager.close(true, true, false, last, false);
+        } catch (final Throwable thr) {
+            LOGGER.error("Failed to save chunks for region around chunk " + center + " in world '" + region.regioniser.world.getWorld().getName() + "'", thr);
+        } finally {
+            this.shuttingDown = null;
+        }
+    }
+
+    private void haltChunkSystem(final ServerLevel world) {
+        try {
+            world.chunkTaskScheduler.chunkHolderManager.close(false, true, true, false, false);
+        } catch (final Throwable thr) {
+            LOGGER.error("Failed to halt chunk system for world '" + world.getWorld().getName() + "'", thr);
+        }
+    }
+
+    private void haltWorldNoRegions(final ServerLevel world) {
+        try {
+            world.chunkTaskScheduler.chunkHolderManager.close(true, true, true, true, false);
+        } catch (final Throwable thr) {
+            LOGGER.error("Failed to close world '" + world.getWorld().getName() + "' with no regions", thr);
+        }
+    }
+
+    @Override
+    public final void run() {
+        // await scheduler termination
+        LOGGER.info("Awaiting scheduler termination for 60s");
+        if (TickRegions.getScheduler().halt(true, TimeUnit.SECONDS.toNanos(60L))) {
+            LOGGER.info("Scheduler halted");
+        } else {
+            LOGGER.warn("Scheduler did not terminate within 60s, proceeding with shutdown anyways");
+            TickRegions.getScheduler().dumpAliveThreadTraces("Did not shut down in time");
+        }
+
+        MinecraftServer.getServer().stopServer(); // stop part 1: most logic, kicking players, plugins, etc
+        // halt all chunk systems first so that any in-progress chunk generation stops
+        LOGGER.info("Halting chunk systems");
+        for (final ServerLevel world : MinecraftServer.getServer().getAllLevels()) {
+            try {
+                world.chunkTaskScheduler.halt(false, 0L);
+            } catch (final Throwable throwable) {
+                LOGGER.error("Failed to soft halt chunk system for world '" + world.getWorld().getName() + "'", throwable);
+            }
+        }
+        for (final ServerLevel world : MinecraftServer.getServer().getAllLevels()) {
+            this.haltChunkSystem(world);
+        }
+        LOGGER.info("Halted chunk systems");
+        for (final ServerLevel world : MinecraftServer.getServer().getAllLevels()) {
+            final List<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>>
+                regions = new ArrayList<>();
+            world.regioniser.computeForAllRegionsUnsynchronised(regions::add);
+
+            for (int i = 0, len = regions.size(); i < len; ++i) {
+                final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region = regions.get(i);
+                this.finishTeleportations(region, world);
+            }
+
+            for (int i = 0, len = regions.size(); i < len; ++i) {
+                final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region = regions.get(i);
+                this.saveRegionChunks(region, (i + 1) == len);
+            }
+
+            this.saveLevelData(world);
+        }
+        // moved from stop part 1
+        // we need this to be after saving level data, as that will complete any teleportations the player is in
+        LOGGER.info("Saving players");
+        MinecraftServer.getServer().getPlayerList().saveAll();
+
+        MinecraftServer.getServer().stopPart2(); // stop part 2: close other resources (io thread, etc)
+        // done, part 2 should call exit()
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/RegionizedData.java b/src/main/java/io/papermc/paper/threadedregions/RegionizedData.java
new file mode 100644
index 0000000000000000000000000000000000000000..1f48ada99d6d24880f9bda1cd05d41a4562e42f5
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionizedData.java
@@ -0,0 +1,235 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.util.Validate;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
+import net.minecraft.server.level.ServerLevel;
+import javax.annotation.Nullable;
+import java.util.function.Supplier;
+
+/**
+ * Use to manage data that needs to be regionised.
+ * <p>
+ *     <b>Note:</b> that unlike {@link ThreadLocal}, regionised data is not deleted once the {@code RegionizedData} object is GC'd.
+ *     The data is held in reference to the world it resides in.
+ * </p>
+ * <P>
+ *     <b>Note:</b> Keep in mind that when regionised ticking is disabled, the entire server is considered a single region.
+ *     That is, the data may or may not cross worlds. As such, the {@code RegionizedData} object must be instanced
+ *     per world when appropriate, as it is no longer guaranteed that separate worlds contain separate regions.
+ *     See below for more details on instancing per world.
+ * </P>
+ * <p>
+ *     Regionised data may be <b>world-checked</b>. That is, {@link #get()} may throw an exception if the current
+ *     region's world does not match the {@code RegionizedData}'s world. Consider the usages of {@code RegionizedData} below
+ *     see why the behavior may or may not be desirable:
+ *     <pre>
+ *         {@code
+ *         public class EntityTickList {
+ *             private final List<Entity> entities = new ArrayList<>();
+ *
+ *             public void addEntity(Entity e) {
+ *                 this.entities.add(e);
+ *             }
+ *
+ *             public void removeEntity(Entity e) {
+ *                 this.entities.remove(e);
+ *             }
+ *         }
+ *
+ *         public class World {
+ *
+ *             // callback is left out of this example
+ *             // note: world != null here
+ *             public final RegionizedData<EntityTickList> entityTickLists =
+ *                 new RegionizedData<>(this, () -> new EntityTickList(), ...);
+ *
+ *             public void addTickingEntity(Entity e) {
+ *                 // What we expect here is that this world is the
+ *                 // current ticking region's world.
+ *                 // If that is true, then calling this.entityTickLists.get()
+ *                 // will retrieve the current region's EntityTickList
+ *                 // for this world, which is fine since the current
+ *                 // region is contained within this world.
+ *
+ *                 // But if the current region's world is not this world,
+ *                 // and if the world check is disabled, then we will actually
+ *                 // retrieve _this_ world's EntityTickList for the region,
+ *                 // and NOT the EntityTickList for the region's world.
+ *                 // This is because the RegionizedData object is instantiated
+ *                 // per world.
+ *                 this.entityTickLists.get().addEntity(e);
+ *             }
+ *         }
+ *
+ *         public class TickTimes {
+ *
+ *             private final List<Long> tickTimesNS = new ArrayList<>();
+ *
+ *             public void completeTick(long timeNS) {
+ *                 this.tickTimesNS.add(timeNS);
+ *             }
+ *
+ *             public double getAverageTickLengthMS() {
+ *                 double sum = 0.0;
+ *                 for (long time : tickTimesNS) {
+ *                     sum += (double)time;
+ *                 }
+ *                 return (sum / this.tickTimesNS.size()) / 1.0E6; // 1ms = 1 million ns
+ *             }
+ *         }
+ *
+ *         public class Server {
+ *             public final List<World> worlds = ...;
+ *
+ *             // callback is left out of this example
+ *             // note: world == null here, because this RegionizedData object
+ *             // is not instantiated per world, but rather globally.
+ *             public final RegionizedData<TickTimes> tickTimes =
+ *                  new RegionizedData<>(null, () -> new TickTimes(), ...);
+ *         }
+ *         }
+ *     </pre>
+ *     In general, it is advised that if a RegionizedData object is instantiated <i>per world</i>, that world checking
+ *     is enabled for it by passing the world to the constructor.
+ * </p>
+ */
+public final class RegionizedData<T> {
+
+    private final ServerLevel world;
+    private final Supplier<T> initialValueSupplier;
+    private final RegioniserCallback<T> callback;
+
+    /**
+     * Creates a regionised data holder. The provided initial value supplier may not be null, and it must
+     * never produce {@code null} values.
+     * <p>
+     *     Note that the supplier or regioniser callback may be used while the region lock is held, so any blocking
+     *     operations may deadlock the entire server and as such the function should be completely non-blocking
+     *     and must complete in a timely manner.
+     * </p>
+     * <p>
+     *     If the provided world is {@code null}, then the world checks are disabled. The world should only ever
+     *     be {@code null} if the data is specifically not specific to worlds. For example, using {@code null}
+     *     for an entity tick list is invalid since the entities are tied to a world <b>and</b> region,
+     *     however using {@code null} for tasks to run at the end of a tick is valid since the tasks are tied to
+     *     region <b>only</b>.
+     * </p>
+     * @param world The world in which the region data resides.
+     * @param supplier Initial value supplier used to lazy initialise region data.
+     * @param callback Region callback to manage this regionised data.
+     */
+    public RegionizedData(final ServerLevel world, final Supplier<T> supplier, final RegioniserCallback<T> callback) {
+        this.world = world;
+        this.initialValueSupplier = Validate.notNull(supplier, "Supplier may not be null.");
+        this.callback = Validate.notNull(callback, "Regioniser callback may not be null.");
+    }
+
+    T createNewValue() {
+        return Validate.notNull(this.initialValueSupplier.get(), "Initial value supplier may not return null");
+    }
+
+    RegioniserCallback<T> getCallback() {
+        return this.callback;
+    }
+
+    /**
+     * Returns the current data type for the current ticking region. If there is no region, returns {@code null}.
+     * @return the current data type for the current ticking region. If there is no region, returns {@code null}.
+     * @throws IllegalStateException If the following are true: The server is in region ticking mode,
+     *                               this {@code RegionizedData}'s world is not {@code null},
+     *                               and the current ticking region's world does not match this {@code RegionizedData}'s world.
+     */
+    public @Nullable T get() {
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+
+        if (region == null) {
+            return null;
+        }
+
+        if (this.world != null && this.world != region.getData().world) {
+            throw new IllegalStateException("World check failed: expected world: " + this.world.getWorld().getKey() + ", region world: " + region.getData().world.getWorld().getKey());
+        }
+
+        return region.getData().getOrCreateRegionizedData(this);
+    }
+
+    /**
+     * Class responsible for handling merge / split requests from the regioniser.
+     * <p>
+     *     It is critical to note that each function is called while holding the region lock.
+     * </p>
+     */
+    public static interface RegioniserCallback<T> {
+
+        /**
+         * Completely merges the data in {@code from} to {@code into}.
+         * <p>
+         *     <b>Calculating Tick Offsets:</b>
+         *     Sometimes data stores absolute tick deadlines, and since regions tick independently, absolute deadlines
+         *     are not comparable across regions. Consider absolute deadlines {@code deadlineFrom, deadlineTo} in
+         *     regions {@code from} and {@code into} respectively. We can calculate the relative deadline for the from
+         *     region with {@code relFrom = deadlineFrom - currentTickFrom}. Then, we can use the same equation for
+         *     computing the absolute deadline in region {@code into} that has the same relative deadline as {@code from}
+         *     as {@code deadlineTo = relFrom + currentTickTo}. By substituting {@code relFrom} as {@code deadlineFrom - currentTickFrom},
+         *     we finally have that {@code deadlineTo = deadlineFrom + (currentTickTo - currentTickFrom)} and
+         *     that we can use an offset {@code fromTickOffset = currentTickTo - currentTickFrom} to calculate
+         *     {@code deadlineTo} as {@code deadlineTo = deadlineFrom + fromTickOffset}.
+         * </p>
+         * <p>
+         *     <b>Critical Notes:</b>
+         *     <li>
+         *         <ul>
+         *             This function is called while the region lock is held, so any blocking operations may
+         *             deadlock the entire server and as such the function should be completely non-blocking and must complete
+         *             in a timely manner.
+         *         </ul>
+         *         <ul>
+         *             This function may not throw any exceptions, or the server will be left in an unrecoverable state.
+         *         </ul>
+         *     </li>
+         * </p>
+         *
+         * @param from The data to merge from.
+         * @param into The data to merge into.
+         * @param fromTickOffset The addend to absolute tick deadlines stored in the {@code from} region to adjust to the into region.
+         */
+        public void merge(final T from, final T into, final long fromTickOffset);
+
+        /**
+         * Splits the data in {@code from} into {@code dataSet}.
+         * <p>
+         *     The chunk coordinate to region section coordinate bit shift amount is provided in {@code chunkToRegionShift}.
+         *     To convert from chunk coordinates to region coordinates and keys, see the code below:
+         *     <pre>
+         *         {@code
+         *         int chunkX = ...;
+         *         int chunkZ = ...;
+         *
+         *         int regionSectionX = chunkX >> chunkToRegionShift;
+         *         int regionSectionZ = chunkZ >> chunkToRegionShift;
+         *         long regionSectionKey = io.papermc.paper.util.CoordinateUtils.getChunkKey(regionSectionX, regionSectionZ);
+         *         }
+         *     </pre>
+         * </p>
+         * <p>
+         *     The {@code regionToData} hashtable provides a lookup from {@code regionSectionKey} (see above) to the
+         *     data that is owned by the region which occupies the region section.
+         * </p>
+         * <p>
+         *     Unlike {@link #merge(Object, Object, long)}, there is no absolute tick offset provided. This is because
+         *     the new regions formed from the split will start at the same tick number, and so no adjustment is required.
+         * </p>
+         *
+         * @param from The data to split from.
+         * @param chunkToRegionShift The signed right-shift value used to convert chunk coordinates into region section coordinates.
+         * @param regionToData Lookup hash table from region section key to .
+         * @param dataSet The data set to split into.
+         */
+        public void split(
+            final T from, final int chunkToRegionShift,
+            final Long2ReferenceOpenHashMap<T> regionToData, final ReferenceOpenHashSet<T> dataSet
+        );
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/RegionizedServer.java b/src/main/java/io/papermc/paper/threadedregions/RegionizedServer.java
new file mode 100644
index 0000000000000000000000000000000000000000..fc3d332aa1c1d469cedfe2aaa7102dcd78e25642
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionizedServer.java
@@ -0,0 +1,455 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue;
+import ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.threadedregions.scheduler.FoliaGlobalRegionScheduler;
+import io.papermc.paper.util.TickThread;
+import net.minecraft.CrashReport;
+import net.minecraft.ReportedException;
+import net.minecraft.network.Connection;
+import net.minecraft.network.PacketListener;
+import net.minecraft.network.PacketSendListener;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.MutableComponent;
+import net.minecraft.network.protocol.common.ClientboundDisconnectPacket;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.dedicated.DedicatedServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import net.minecraft.world.level.GameRules;
+import org.bukkit.Bukkit;
+import org.slf4j.Logger;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.BooleanSupplier;
+
+public final class RegionizedServer {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+    private static final RegionizedServer INSTANCE = new RegionizedServer();
+
+    public final RegionizedTaskQueue taskQueue = new RegionizedTaskQueue();
+
+    private final CopyOnWriteArrayList<ServerLevel> worlds = new CopyOnWriteArrayList<>();
+    private final CopyOnWriteArrayList<Connection> connections = new CopyOnWriteArrayList<>();
+
+    private final MultiThreadedQueue<Runnable> globalTickQueue = new MultiThreadedQueue<>();
+
+    private final GlobalTickTickHandle tickHandle = new GlobalTickTickHandle(this);
+
+    public static RegionizedServer getInstance() {
+        return INSTANCE;
+    }
+
+    public void addConnection(final Connection conn) {
+        this.connections.add(conn);
+    }
+
+    public boolean removeConnection(final Connection conn) {
+        return this.connections.remove(conn);
+    }
+
+    public void addWorld(final ServerLevel world) {
+        this.worlds.add(world);
+    }
+
+    public void init() {
+        // call init event _before_ scheduling anything
+        new RegionizedServerInitEvent().callEvent();
+
+        // now we can schedule
+        this.tickHandle.setInitialStart(System.nanoTime() + TickRegionScheduler.TIME_BETWEEN_TICKS);
+        TickRegions.getScheduler().scheduleRegion(this.tickHandle);
+        TickRegions.getScheduler().init();
+    }
+
+    public void invalidateStatus() {
+        this.lastServerStatus = 0L;
+    }
+
+    public void addTaskWithoutNotify(final Runnable run) {
+        this.globalTickQueue.add(run);
+    }
+
+    public void addTask(final Runnable run) {
+        this.addTaskWithoutNotify(run);
+        TickRegions.getScheduler().setHasTasks(this.tickHandle);
+    }
+
+    /**
+     * Returns the current tick of the region ticking.
+     * @throws IllegalStateException If there is no current region.
+     */
+    public static long getCurrentTick() throws IllegalStateException {
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            if (TickThread.isShutdownThread()) {
+                return 0L;
+            }
+            throw new IllegalStateException("No currently ticking region");
+        }
+        return region.getData().getCurrentTick();
+    }
+
+    public static boolean isGlobalTickThread() {
+        return INSTANCE.tickHandle == TickRegionScheduler.getCurrentTickingTask();
+    }
+
+    public static void ensureGlobalTickThread(final String reason) {
+        if (!isGlobalTickThread()) {
+            throw new IllegalStateException(reason);
+        }
+    }
+
+    public static TickRegionScheduler.RegionScheduleHandle getGlobalTickData() {
+        return INSTANCE.tickHandle;
+    }
+
+    private static final class GlobalTickTickHandle extends TickRegionScheduler.RegionScheduleHandle {
+
+        private final RegionizedServer server;
+
+        private final AtomicBoolean scheduled = new AtomicBoolean();
+        private final AtomicBoolean ticking = new AtomicBoolean();
+
+        public GlobalTickTickHandle(final RegionizedServer server) {
+            super(null, SchedulerThreadPool.DEADLINE_NOT_SET);
+            this.server = server;
+        }
+
+        /**
+         * Only valid to call BEFORE scheduled!!!!
+         */
+        final void setInitialStart(final long start) {
+            if (this.scheduled.getAndSet(true)) {
+                throw new IllegalStateException("Double scheduling global tick");
+            }
+            this.updateScheduledStart(start);
+        }
+
+        @Override
+        protected boolean tryMarkTicking() {
+            return !this.ticking.getAndSet(true);
+        }
+
+        @Override
+        protected boolean markNotTicking() {
+            return this.ticking.getAndSet(false);
+        }
+
+        @Override
+        protected void tickRegion(final int tickCount, final long startTime, final long scheduledEnd) {
+            this.drainTasks();
+            this.server.globalTick(tickCount);
+        }
+
+        private void drainTasks() {
+            while (this.runOneTask());
+        }
+
+        private boolean runOneTask() {
+            final Runnable run = this.server.globalTickQueue.poll();
+            if (run == null) {
+                return false;
+            }
+
+            // TODO try catch?
+            run.run();
+
+            return true;
+        }
+
+        @Override
+        protected boolean runRegionTasks(final BooleanSupplier canContinue) {
+            do {
+                if (!this.runOneTask()) {
+                    return false;
+                }
+            } while (canContinue.getAsBoolean());
+
+            return true;
+        }
+
+        @Override
+        protected boolean hasIntermediateTasks() {
+            return !this.server.globalTickQueue.isEmpty();
+        }
+    }
+
+    private long lastServerStatus;
+    private long tickCount;
+
+    /*
+    private final java.util.Random random = new java.util.Random(4L);
+    private final List<io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.SingleUserAreaMap<Void>> walkers =
+        new java.util.ArrayList<>();
+    static final int PLAYERS = 500;
+    static final int RAD_BLOCKS = 1000;
+    static final int RAD = RAD_BLOCKS >> 4;
+    static final int RAD_BIG_BLOCKS = 100_000;
+    static final int RAD_BIG = RAD_BIG_BLOCKS >> 4;
+    static final int VD = 4 + 12;
+    static final int BIG_PLAYERS = 250;
+    static final double WALK_CHANCE = 0.3;
+    static final double TP_CHANCE = 0.2;
+    static final double TASK_CHANCE = 0.2;
+
+    private ServerLevel getWorld() {
+        return this.worlds.get(0);
+    }
+
+    private void init2() {
+        for (int i = 0; i < PLAYERS; ++i) {
+            int rad = i < BIG_PLAYERS ? RAD_BIG : RAD;
+            int posX = this.random.nextInt(-rad, rad + 1);
+            int posZ = this.random.nextInt(-rad, rad + 1);
+
+            io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.SingleUserAreaMap<Void> map = new io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.SingleUserAreaMap<>(null) {
+                @Override
+                protected void addCallback(Void parameter, int chunkX, int chunkZ) {
+                    ServerLevel world = RegionizedServer.this.getWorld();
+                    if (RegionizedServer.this.random.nextDouble() <= TASK_CHANCE) {
+                        RegionizedServer.this.taskQueue.queueChunkTask(world, chunkX, chunkZ, () -> {
+                            RegionizedServer.this.taskQueue.queueChunkTask(world, chunkX, chunkZ, () -> {});
+                        });
+                    }
+                    world.chunkTaskScheduler.chunkHolderManager.addTicketAtLevel(
+                        net.minecraft.server.level.TicketType.PLAYER, chunkX, chunkZ, io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL, new net.minecraft.world.level.ChunkPos(posX, posZ)
+                    );
+                }
+
+                @Override
+                protected void removeCallback(Void parameter, int chunkX, int chunkZ) {
+                    ServerLevel world = RegionizedServer.this.getWorld();
+                    if (RegionizedServer.this.random.nextDouble() <= TASK_CHANCE) {
+                        RegionizedServer.this.taskQueue.queueChunkTask(world, chunkX, chunkZ, () -> {
+                            RegionizedServer.this.taskQueue.queueChunkTask(world, chunkX, chunkZ, () -> {});
+                        });
+                    }
+                    world.chunkTaskScheduler.chunkHolderManager.removeTicketAtLevel(
+                        net.minecraft.server.level.TicketType.PLAYER, chunkX, chunkZ, io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL, new net.minecraft.world.level.ChunkPos(posX, posZ)
+                    );
+                }
+            };
+
+            map.add(posX, posZ, VD);
+
+            walkers.add(map);
+        }
+    }
+
+    private void randomWalk() {
+        if (this.walkers.isEmpty()) {
+            this.init2();
+            return;
+        }
+
+        for (int i = 0; i < PLAYERS; ++i) {
+            if (this.random.nextDouble() > WALK_CHANCE) {
+                continue;
+            }
+
+            io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.SingleUserAreaMap<Void> map = this.walkers.get(i);
+
+            int updateX = this.random.nextInt(-1, 2);
+            int updateZ = this.random.nextInt(-1, 2);
+
+            map.update(map.lastChunkX + updateX, map.lastChunkZ + updateZ, VD);
+        }
+
+        for (int i = 0; i < PLAYERS; ++i) {
+            if (random.nextDouble() >= TP_CHANCE) {
+                continue;
+            }
+
+            int rad = i < BIG_PLAYERS ? RAD_BIG : RAD;
+            int posX = random.nextInt(-rad, rad + 1);
+            int posZ = random.nextInt(-rad, rad + 1);
+
+            io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.SingleUserAreaMap<Void> map = walkers.get(i);
+
+            map.update(posX, posZ, VD);
+        }
+    }
+     */
+
+    private void globalTick(final int tickCount) {
+        /*
+        if (false) {
+            io.papermc.paper.threadedregions.ThreadedTicketLevelPropagator.main(null);
+        }
+        this.randomWalk();
+         */
+        ++this.tickCount;
+        // expire invalid click command callbacks
+        io.papermc.paper.adventure.providers.ClickCallbackProviderImpl.CALLBACK_MANAGER.handleQueue((int)this.tickCount);
+
+        // scheduler
+        ((FoliaGlobalRegionScheduler)Bukkit.getGlobalRegionScheduler()).tick();
+
+        // commands
+        ((DedicatedServer)MinecraftServer.getServer()).handleConsoleInputs();
+
+        // needs
+        // player ping sample
+        // world global tick
+        // connection tick
+
+        // tick player ping sample
+        this.tickPlayerSample();
+
+        // tick worlds
+        for (final ServerLevel world : this.worlds) {
+            this.globalTick(world, tickCount);
+        }
+
+        // tick connections
+        this.tickConnections();
+
+        // player list
+        MinecraftServer.getServer().getPlayerList().tick();
+    }
+
+    private void tickPlayerSample() {
+        final MinecraftServer mcServer = MinecraftServer.getServer();
+
+        final long currtime = System.nanoTime();
+
+        // player ping sample
+        // copied from MinecraftServer#tickServer
+        // note: we need to reorder setPlayers to be the last operation it does, rather than the first to avoid publishing
+        // an uncomplete status
+        if (currtime - this.lastServerStatus >= MinecraftServer.STATUS_EXPIRE_TIME_NANOS) {
+            this.lastServerStatus = currtime;
+            mcServer.rebuildServerStatus();
+        }
+    }
+
+    public static boolean isNotOwnedByGlobalRegion(final Connection conn) {
+        final PacketListener packetListener = conn.getPacketListener();
+
+        if (packetListener instanceof ServerGamePacketListenerImpl gamePacketListener) {
+            return !gamePacketListener.waitingForSwitchToConfig;
+        }
+
+        if (conn.getPacketListener() instanceof net.minecraft.server.network.ServerConfigurationPacketListenerImpl configurationPacketListener) {
+            return configurationPacketListener.switchToMain;
+        }
+
+        return false;
+    }
+
+    private void tickConnections() {
+        final List<Connection> connections = new ArrayList<>(this.connections);
+        Collections.shuffle(connections); // shuffle to prevent people from "gaming" the server by re-logging
+        for (final Connection conn : connections) {
+            if (!conn.becomeActive()) {
+                continue;
+            }
+
+            if (isNotOwnedByGlobalRegion(conn)) {
+                // we actually require that the owning regions remove the connection for us, as it is possible
+                // that ownership is transferred back to us
+                continue;
+            }
+
+            if (!conn.isConnected()) {
+                this.removeConnection(conn);
+                conn.handleDisconnection();
+                continue;
+            }
+
+            try {
+                conn.tick();
+            } catch (final Exception exception) {
+                if (conn.isMemoryConnection()) {
+                    throw new ReportedException(CrashReport.forThrowable(exception, "Ticking memory connection"));
+                }
+
+                LOGGER.warn("Failed to handle packet for {}", conn.getLoggableAddress(MinecraftServer.getServer().logIPs()), exception);
+                MutableComponent ichatmutablecomponent = Component.literal("Internal server error");
+
+                conn.send(new ClientboundDisconnectPacket(ichatmutablecomponent), PacketSendListener.thenRun(() -> {
+                    conn.disconnect(ichatmutablecomponent);
+                }));
+                conn.setReadOnly();
+                continue;
+            }
+        }
+    }
+
+    // A global tick only updates things like weather / worldborder, basically anything in the world that is
+    // NOT tied to a specific region, but rather shared amongst all of them.
+    private void globalTick(final ServerLevel world, final int tickCount) {
+        // needs
+        // worldborder tick
+        // advancing the weather cycle
+        // sleep status thing
+        // updating sky brightness
+        // time ticking (game time + daylight), plus PrimayLevelDat#getScheduledEvents ticking
+
+        // Typically, we expect there to be a running region to drain a world's global chunk tasks. However,
+        // this may not be the case - and thus, only the global tick thread can do anything.
+        world.taskQueueRegionData.drainGlobalChunkTasks();
+
+        // worldborder tick
+        this.tickWorldBorder(world);
+
+        // weather cycle
+        this.advanceWeatherCycle(world);
+
+        // sleep status
+        this.checkNightSkip(world);
+
+        // update raids
+        this.updateRaids(world);
+
+        // sky brightness
+        this.updateSkyBrightness(world);
+
+        // time ticking (TODO API synchronisation?)
+        this.tickTime(world, tickCount);
+
+        world.updateTickData();
+
+        world.chunkTaskScheduler.chunkHolderManager.processTicketUpdates(); // required to eventually process ticket updates
+    }
+
+    private void updateRaids(final ServerLevel world) {
+        world.getRaids().globalTick();
+    }
+
+    private void checkNightSkip(final ServerLevel world) {
+        world.tickSleep();
+    }
+
+    private void advanceWeatherCycle(final ServerLevel world) {
+        world.advanceWeatherCycle();
+    }
+
+    private void updateSkyBrightness(final ServerLevel world) {
+        world.updateSkyBrightness();
+    }
+
+    private void tickWorldBorder(final ServerLevel world) {
+        world.getWorldBorder().tick();
+    }
+
+    private void tickTime(final ServerLevel world, final int tickCount) {
+        if (world.tickTime) {
+            if (world.levelData.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT)) {
+                world.setDayTime(world.levelData.getDayTime() + (long)tickCount);
+            }
+            world.serverLevelData.setGameTime(world.serverLevelData.getGameTime() + (long)tickCount);
+        }
+    }
+
+    public static final record WorldLevelData(ServerLevel world, long nonRedstoneGameTime, long dayTime) {
+
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/RegionizedTaskQueue.java b/src/main/java/io/papermc/paper/threadedregions/RegionizedTaskQueue.java
new file mode 100644
index 0000000000000000000000000000000000000000..98ddb674b63a4777a98152ea960debf48aa2bc35
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionizedTaskQueue.java
@@ -0,0 +1,768 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue;
+import ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor;
+import ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable;
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import io.papermc.paper.chunk.system.scheduling.ChunkHolderManager;
+import io.papermc.paper.util.CoordinateUtils;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.Reference2ReferenceMap;
+import it.unimi.dsi.fastutil.objects.Reference2ReferenceOpenHashMap;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.TicketType;
+import net.minecraft.util.Unit;
+import java.lang.invoke.VarHandle;
+import java.util.ArrayDeque;
+import java.util.Iterator;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.ReentrantLock;
+
+public final class RegionizedTaskQueue {
+
+    private static final TicketType<Unit> TASK_QUEUE_TICKET = TicketType.create("task_queue_ticket", (a, b) -> 0);
+
+    public PrioritisedExecutor.PrioritisedTask createChunkTask(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                               final Runnable run) {
+        return new PrioritisedQueue.ChunkBasedPriorityTask(world.taskQueueRegionData, chunkX, chunkZ, true, run, PrioritisedExecutor.Priority.NORMAL);
+    }
+
+    public PrioritisedExecutor.PrioritisedTask createChunkTask(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                               final Runnable run, final PrioritisedExecutor.Priority priority) {
+        return new PrioritisedQueue.ChunkBasedPriorityTask(world.taskQueueRegionData, chunkX, chunkZ, true, run, priority);
+    }
+
+    public PrioritisedExecutor.PrioritisedTask createTickTaskQueue(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                                   final Runnable run) {
+        return new PrioritisedQueue.ChunkBasedPriorityTask(world.taskQueueRegionData, chunkX, chunkZ, false, run, PrioritisedExecutor.Priority.NORMAL);
+    }
+
+    public PrioritisedExecutor.PrioritisedTask createTickTaskQueue(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                                   final Runnable run, final PrioritisedExecutor.Priority priority) {
+        return new PrioritisedQueue.ChunkBasedPriorityTask(world.taskQueueRegionData, chunkX, chunkZ, false, run, priority);
+    }
+
+    public PrioritisedExecutor.PrioritisedTask queueChunkTask(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                              final Runnable run) {
+        return this.queueChunkTask(world, chunkX, chunkZ, run, PrioritisedExecutor.Priority.NORMAL);
+    }
+
+    public PrioritisedExecutor.PrioritisedTask queueChunkTask(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                              final Runnable run, final PrioritisedExecutor.Priority priority) {
+        final PrioritisedExecutor.PrioritisedTask ret = this.createChunkTask(world, chunkX, chunkZ, run, priority);
+        ret.queue();
+        return ret;
+    }
+
+    public PrioritisedExecutor.PrioritisedTask queueTickTaskQueue(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                                  final Runnable run) {
+        return this.queueTickTaskQueue(world, chunkX, chunkZ, run, PrioritisedExecutor.Priority.NORMAL);
+    }
+
+    public PrioritisedExecutor.PrioritisedTask queueTickTaskQueue(final ServerLevel world, final int chunkX, final int chunkZ,
+                                                                  final Runnable run, final PrioritisedExecutor.Priority priority) {
+        final PrioritisedExecutor.PrioritisedTask ret = this.createTickTaskQueue(world, chunkX, chunkZ, run, priority);
+        ret.queue();
+        return ret;
+    }
+
+    public static final class WorldRegionTaskData {
+        private final ServerLevel world;
+        private final MultiThreadedQueue<Runnable> globalChunkTask = new MultiThreadedQueue<>();
+        private final java.util.concurrent.ConcurrentHashMap<io.papermc.paper.chunk.system.io.RegionFileIOThread.ChunkCoordinate, AtomicLong> referenceCounters = new java.util.concurrent.ConcurrentHashMap<>(); // Folia - use area based lock to reduce contention
+
+        public WorldRegionTaskData(final ServerLevel world) {
+            this.world = world;
+        }
+
+        private boolean executeGlobalChunkTask() {
+            final Runnable run = this.globalChunkTask.poll();
+            if (run != null) {
+                run.run();
+                return true;
+            }
+            return false;
+        }
+
+        public void drainGlobalChunkTasks() {
+            while (this.executeGlobalChunkTask());
+        }
+
+        public void pushGlobalChunkTask(final Runnable run) {
+            this.globalChunkTask.add(run);
+        }
+
+        private PrioritisedQueue getQueue(final boolean synchronise, final int chunkX, final int chunkZ, final boolean isChunkTask) {
+            final ThreadedRegionizer<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regioniser = this.world.regioniser;
+            final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region
+                = synchronise ? regioniser.getRegionAtSynchronised(chunkX, chunkZ) : regioniser.getRegionAtUnsynchronised(chunkX, chunkZ);
+            if (region == null) {
+                return null;
+            }
+            final RegionTaskQueueData taskQueueData = region.getData().getTaskQueueData();
+            return (isChunkTask ? taskQueueData.chunkQueue : taskQueueData.tickTaskQueue);
+        }
+
+        private void removeTicket(final long coord) {
+            this.world.chunkTaskScheduler.chunkHolderManager.removeTicketAtLevel(
+                TASK_QUEUE_TICKET, coord, ChunkHolderManager.MAX_TICKET_LEVEL, Unit.INSTANCE
+            );
+        }
+
+        private void addTicket(final long coord) {
+            this.world.chunkTaskScheduler.chunkHolderManager.addTicketAtLevel(
+                TASK_QUEUE_TICKET, coord, ChunkHolderManager.MAX_TICKET_LEVEL, Unit.INSTANCE
+            );
+        }
+
+        // Folia start - use area based lock to reduce contention
+        private void processTicketUpdates(final long coord) {
+            this.world.chunkTaskScheduler.chunkHolderManager.processTicketUpdates(CoordinateUtils.getChunkX(coord), CoordinateUtils.getChunkZ(coord));
+        }
+        // Folia end - use area based lock to reduce contention
+
+        private void decrementReference(final AtomicLong reference, final long coord) {
+            final long val = reference.decrementAndGet();
+            if (val == 0L) {
+                final int chunkX = CoordinateUtils.getChunkX(coord); // Folia - use area based lock to reduce contention
+                final int chunkZ = CoordinateUtils.getChunkZ(coord); // Folia - use area based lock to reduce contention
+                final io.papermc.paper.chunk.system.io.RegionFileIOThread.ChunkCoordinate key = new io.papermc.paper.chunk.system.io.RegionFileIOThread.ChunkCoordinate(coord); // Folia - use area based lock to reduce contention
+                final ca.spottedleaf.concurrentutil.lock.ReentrantAreaLock.Node ticketLock = this.world.chunkTaskScheduler.chunkHolderManager.ticketLockArea.lock(chunkX, chunkZ); // Folia - use area based lock to reduce contention
+                try {
+                    if (this.referenceCounters.remove(key, reference)) { // Folia - use area based lock to reduce contention
+                        WorldRegionTaskData.this.removeTicket(coord);
+                    } // else: race condition, something replaced our reference - not our issue anymore
+                } finally {
+                    this.world.chunkTaskScheduler.chunkHolderManager.ticketLockArea.unlock(ticketLock); // Folia - use area based lock to reduce contention
+                }
+            } else if (val < 0L) {
+                throw new IllegalStateException("Reference count < 0: " + val);
+            }
+        }
+
+        private AtomicLong incrementReference(final long coord) {
+            final io.papermc.paper.chunk.system.io.RegionFileIOThread.ChunkCoordinate key = new io.papermc.paper.chunk.system.io.RegionFileIOThread.ChunkCoordinate(coord); // Folia - use area based lock to reduce contention
+            final AtomicLong ret = this.referenceCounters.get(key); // Folia - use area based lock to reduce contention
+            if (ret != null) {
+                // try to fast acquire counter
+                int failures = 0;
+                for (long curr = ret.get();;) {
+                    if (curr == 0L) {
+                        // failed to fast acquire as reference expired
+                        break;
+                    }
+
+                    for (int i = 0; i < failures; ++i) {
+                        ConcurrentUtil.backoff();
+                    }
+
+                    if (curr == (curr = ret.compareAndExchange(curr, curr + 1L))) {
+                        return ret;
+                    }
+
+                    ++failures;
+                }
+            }
+
+            // slow acquire
+            final int chunkX = CoordinateUtils.getChunkX(coord); // Folia - use area based lock to reduce contention
+            final int chunkZ = CoordinateUtils.getChunkZ(coord); // Folia - use area based lock to reduce contention
+            final ca.spottedleaf.concurrentutil.lock.ReentrantAreaLock.Node ticketLock = this.world.chunkTaskScheduler.chunkHolderManager.ticketLockArea.lock(chunkX, chunkZ); // Folia - use area based lock to reduce contention
+            final AtomicLong ret2;
+            final boolean processTicketUpdates;
+            try {
+                final AtomicLong replace = new AtomicLong(1L);
+                final AtomicLong valueInMap = this.referenceCounters.putIfAbsent(key, replace); // Folia - use area based lock to reduce contention
+                if (valueInMap == null) {
+                    // replaced, we should usually be here
+                    this.addTicket(coord);
+                    ret2 = replace;
+                    processTicketUpdates = true;
+                } else {
+                    processTicketUpdates = false;
+                    int failures = 0;
+                    for (long curr = valueInMap.get();;) {
+                        if (curr == 0L) {
+                            // don't need to add ticket here, since ticket is only removed during the lock
+                            // we just need to replace the value in the map so that the thread removing fails and doesn't
+                            // remove the ticket (see decrementReference)
+                            this.referenceCounters.put(key, replace); // Folia - use area based lock to reduce contention
+                            ret2 = replace;
+                            break;
+                        }
+
+                        for (int i = 0; i < failures; ++i) {
+                            ConcurrentUtil.backoff();
+                        }
+
+                        if (curr == (curr = valueInMap.compareAndExchange(curr, curr + 1L))) {
+                            // acquired
+                            ret2 = valueInMap;
+                            break;
+                        }
+
+                        ++failures;
+                    }
+                }
+            } finally {
+                this.world.chunkTaskScheduler.chunkHolderManager.ticketLockArea.unlock(ticketLock); // Folia - use area based lock to reduce contention
+            }
+
+            if (processTicketUpdates) {
+                this.processTicketUpdates(coord);
+            }
+
+            return ret2;
+        }
+    }
+
+    public static final class RegionTaskQueueData {
+        private final PrioritisedQueue tickTaskQueue = new PrioritisedQueue();
+        private final PrioritisedQueue chunkQueue = new PrioritisedQueue();
+        private final WorldRegionTaskData worldRegionTaskData;
+
+        public RegionTaskQueueData(final WorldRegionTaskData worldRegionTaskData) {
+            this.worldRegionTaskData = worldRegionTaskData;
+        }
+
+        void mergeInto(final RegionTaskQueueData into) {
+            this.tickTaskQueue.mergeInto(into.tickTaskQueue);
+            this.chunkQueue.mergeInto(into.chunkQueue);
+        }
+
+        public boolean executeTickTask() {
+            return this.tickTaskQueue.executeTask();
+        }
+
+        public boolean executeChunkTask() {
+            return this.worldRegionTaskData.executeGlobalChunkTask() || this.chunkQueue.executeTask();
+        }
+
+        void split(final ThreadedRegionizer<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regioniser,
+                   final Long2ReferenceOpenHashMap<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>> into) {
+            this.tickTaskQueue.split(
+                false, regioniser, into
+            );
+            this.chunkQueue.split(
+                true, regioniser, into
+            );
+        }
+
+        public void drainTasks() {
+            final PrioritisedQueue tickTaskQueue = this.tickTaskQueue;
+            final PrioritisedQueue chunkTaskQueue = this.chunkQueue;
+
+            int allowedTickTasks = tickTaskQueue.getScheduledTasks();
+            int allowedChunkTasks = chunkTaskQueue.getScheduledTasks();
+
+            boolean executeTickTasks = allowedTickTasks > 0;
+            boolean executeChunkTasks = allowedChunkTasks > 0;
+            boolean executeGlobalTasks = true;
+
+            do {
+                executeTickTasks = executeTickTasks && allowedTickTasks-- > 0 && tickTaskQueue.executeTask();
+                executeChunkTasks = executeChunkTasks && allowedChunkTasks-- > 0 && chunkTaskQueue.executeTask();
+                executeGlobalTasks = executeGlobalTasks && this.worldRegionTaskData.executeGlobalChunkTask();
+            } while (executeTickTasks | executeChunkTasks | executeGlobalTasks);
+
+            if (allowedChunkTasks > 0) {
+                // if we executed chunk tasks, we should try to process ticket updates for full status changes
+                this.worldRegionTaskData.world.chunkTaskScheduler.chunkHolderManager.processTicketUpdates();
+            }
+        }
+
+        public boolean hasTasks() {
+            return !this.tickTaskQueue.isEmpty() || !this.chunkQueue.isEmpty();
+        }
+    }
+
+    static final class PrioritisedQueue {
+        private final ArrayDeque<ChunkBasedPriorityTask>[] queues = new ArrayDeque[PrioritisedExecutor.Priority.TOTAL_SCHEDULABLE_PRIORITIES]; {
+            for (int i = 0; i < PrioritisedExecutor.Priority.TOTAL_SCHEDULABLE_PRIORITIES; ++i) {
+                this.queues[i] = new ArrayDeque<>();
+            }
+        }
+        private boolean isDestroyed;
+
+        public int getScheduledTasks() {
+            synchronized (this) {
+                int ret = 0;
+
+                for (final ArrayDeque<ChunkBasedPriorityTask> queue : this.queues) {
+                    ret += queue.size();
+                }
+
+                return ret;
+            }
+        }
+
+        public boolean isEmpty() {
+            final ArrayDeque<ChunkBasedPriorityTask>[] queues = this.queues;
+            final int max = PrioritisedExecutor.Priority.IDLE.priority;
+            synchronized (this) {
+                for (int i = 0; i <= max; ++i) {
+                    if (!queues[i].isEmpty()) {
+                        return false;
+                    }
+                }
+                return true;
+            }
+        }
+
+        public void mergeInto(final PrioritisedQueue target) {
+            synchronized (this) {
+                this.isDestroyed = true;
+                mergeInto(target, this.queues);
+            }
+        }
+
+        private static void mergeInto(final PrioritisedQueue target, final ArrayDeque<ChunkBasedPriorityTask>[] thisQueues) {
+            synchronized (target) {
+                final ArrayDeque<ChunkBasedPriorityTask>[] otherQueues = target.queues;
+                for (int i = 0; i < thisQueues.length; ++i) {
+                    final ArrayDeque<ChunkBasedPriorityTask> fromQ = thisQueues[i];
+                    final ArrayDeque<ChunkBasedPriorityTask> intoQ = otherQueues[i];
+
+                    // it is possible for another thread to queue tasks into the target queue before we do
+                    // since only the ticking region can poll, we don't have to worry about it when they are being queued -
+                    // but when we are merging, we need to ensure order is maintained (notwithstanding priority changes)
+                    // we can ensure order is maintained by adding all of the tasks from the fromQ into the intoQ at the
+                    // front of the queue, but we need to use descending iterator to ensure we do not reverse
+                    // the order of elements from fromQ
+                    for (final Iterator<ChunkBasedPriorityTask> iterator = fromQ.descendingIterator(); iterator.hasNext();) {
+                        intoQ.addFirst(iterator.next());
+                    }
+                }
+            }
+        }
+
+        // into is a map of section coordinate to region
+        public void split(final boolean isChunkData,
+                          final ThreadedRegionizer<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regioniser,
+                          final Long2ReferenceOpenHashMap<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>> into) {
+            final Reference2ReferenceOpenHashMap<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, ArrayDeque<ChunkBasedPriorityTask>[]>
+                split = new Reference2ReferenceOpenHashMap<>();
+            final int shift = regioniser.sectionChunkShift;
+            synchronized (this) {
+                this.isDestroyed = true;
+                // like mergeTarget, we need to be careful about insertion order so we can maintain order when splitting
+
+                // first, build the targets
+                final ArrayDeque<ChunkBasedPriorityTask>[] thisQueues = this.queues;
+                for (int i = 0; i < thisQueues.length; ++i) {
+                    final ArrayDeque<ChunkBasedPriorityTask> fromQ = thisQueues[i];
+
+                    for (final ChunkBasedPriorityTask task : fromQ) {
+                        final int sectionX = task.chunkX >> shift;
+                        final int sectionZ = task.chunkZ >> shift;
+                        final long sectionKey = CoordinateUtils.getChunkKey(sectionX, sectionZ);
+                        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>
+                            region = into.get(sectionKey);
+                        if (region == null) {
+                            throw new IllegalStateException();
+                        }
+
+                        split.computeIfAbsent(region, (keyInMap) -> {
+                            final ArrayDeque<ChunkBasedPriorityTask>[] ret = new ArrayDeque[PrioritisedExecutor.Priority.TOTAL_SCHEDULABLE_PRIORITIES];
+
+                            for (int k = 0; k < ret.length; ++k) {
+                                ret[k] = new ArrayDeque<>();
+                            }
+
+                            return ret;
+                        })[i].add(task);
+                    }
+                }
+
+                // merge the targets into their queues
+                for (final Iterator<Reference2ReferenceMap.Entry<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, ArrayDeque<ChunkBasedPriorityTask>[]>>
+                     iterator = split.reference2ReferenceEntrySet().fastIterator();
+                     iterator.hasNext();) {
+                    final Reference2ReferenceMap.Entry<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, ArrayDeque<ChunkBasedPriorityTask>[]>
+                        entry = iterator.next();
+                    final RegionTaskQueueData taskQueueData = entry.getKey().getData().getTaskQueueData();
+                    mergeInto(isChunkData ? taskQueueData.chunkQueue : taskQueueData.tickTaskQueue, entry.getValue());
+                }
+            }
+        }
+
+        /**
+         * returns null if the task cannot be scheduled, returns false if this task queue is dead, and returns true
+         * if the task was added
+         */
+        private Boolean tryPush(final ChunkBasedPriorityTask task) {
+            final ArrayDeque<ChunkBasedPriorityTask>[] queues = this.queues;
+            synchronized (this) {
+                final PrioritisedExecutor.Priority priority = task.getPriority();
+                if (priority == PrioritisedExecutor.Priority.COMPLETING) {
+                    return null;
+                }
+                if (this.isDestroyed) {
+                    return Boolean.FALSE;
+                }
+                queues[priority.priority].addLast(task);
+                return Boolean.TRUE;
+            }
+        }
+
+        private boolean executeTask() {
+            final ArrayDeque<ChunkBasedPriorityTask>[] queues = this.queues;
+            final int max = PrioritisedExecutor.Priority.IDLE.priority;
+            ChunkBasedPriorityTask task = null;
+            AtomicLong referenceCounter = null;
+            synchronized (this) {
+                if (this.isDestroyed) {
+                    throw new IllegalStateException("Attempting to poll from dead queue");
+                }
+
+                search_loop:
+                for (int i = 0; i <= max; ++i) {
+                    final ArrayDeque<ChunkBasedPriorityTask> queue = queues[i];
+                    while ((task = queue.pollFirst()) != null) {
+                        if ((referenceCounter = task.trySetCompleting(i)) != null) {
+                            break search_loop;
+                        }
+                    }
+                }
+            }
+
+            if (task == null) {
+                return false;
+            }
+
+            try {
+                task.executeInternal();
+            } finally {
+                task.world.decrementReference(referenceCounter, task.sectionLowerLeftCoord);
+            }
+
+            return true;
+        }
+
+        private static final class ChunkBasedPriorityTask implements PrioritisedExecutor.PrioritisedTask {
+
+            private static final AtomicLong REFERENCE_COUNTER_NOT_SET = new AtomicLong(-1L);
+
+            private final WorldRegionTaskData world;
+            private final int chunkX;
+            private final int chunkZ;
+            private final long sectionLowerLeftCoord; // chunk coordinate
+            private final boolean isChunkTask;
+
+            private volatile AtomicLong referenceCounter;
+            private static final VarHandle REFERENCE_COUNTER_HANDLE = ConcurrentUtil.getVarHandle(ChunkBasedPriorityTask.class, "referenceCounter", AtomicLong.class);
+            private Runnable run;
+            private volatile PrioritisedExecutor.Priority priority;
+            private static final VarHandle PRIORITY_HANDLE = ConcurrentUtil.getVarHandle(ChunkBasedPriorityTask.class, "priority", PrioritisedExecutor.Priority.class);
+
+            ChunkBasedPriorityTask(final WorldRegionTaskData world, final int chunkX, final int chunkZ, final boolean isChunkTask,
+                                   final Runnable run, final PrioritisedExecutor.Priority priority) {
+                this.world = world;
+                this.chunkX = chunkX;
+                this.chunkZ = chunkZ;
+                this.isChunkTask = isChunkTask;
+                this.run = run;
+                this.setReferenceCounterPlain(REFERENCE_COUNTER_NOT_SET);
+                this.setPriorityPlain(priority);
+
+                final int regionShift = world.world.regioniser.sectionChunkShift;
+                final int regionMask = (1 << regionShift) - 1;
+
+                this.sectionLowerLeftCoord = CoordinateUtils.getChunkKey(chunkX & ~regionMask, chunkZ & ~regionMask);
+            }
+
+            private PrioritisedExecutor.Priority getPriorityVolatile() {
+                return (PrioritisedExecutor.Priority)PRIORITY_HANDLE.getVolatile(this);
+            }
+
+            private void setPriorityPlain(final PrioritisedExecutor.Priority priority) {
+                PRIORITY_HANDLE.set(this, priority);
+            }
+
+            private void setPriorityVolatile(final PrioritisedExecutor.Priority priority) {
+                PRIORITY_HANDLE.setVolatile(this, priority);
+            }
+
+            private PrioritisedExecutor.Priority compareAndExchangePriority(final PrioritisedExecutor.Priority expect, final PrioritisedExecutor.Priority update) {
+                return (PrioritisedExecutor.Priority)PRIORITY_HANDLE.compareAndExchange(this, expect, update);
+            }
+
+            private void setReferenceCounterPlain(final AtomicLong value) {
+                REFERENCE_COUNTER_HANDLE.set(this, value);
+            }
+
+            private AtomicLong getReferenceCounterVolatile() {
+                return (AtomicLong)REFERENCE_COUNTER_HANDLE.get(this);
+            }
+
+            private AtomicLong compareAndExchangeReferenceCounter(final AtomicLong expect, final AtomicLong update) {
+                return (AtomicLong)REFERENCE_COUNTER_HANDLE.compareAndExchange(this, expect, update);
+            }
+
+            private void executeInternal() {
+                try {
+                    this.run.run();
+                } finally {
+                    this.run = null;
+                }
+            }
+
+            private void cancelInternal() {
+                this.run = null;
+            }
+
+            private boolean tryComplete(final boolean cancel) {
+                int failures = 0;
+                for (AtomicLong curr = this.getReferenceCounterVolatile();;) {
+                    if (curr == null) {
+                        return false;
+                    }
+
+                    for (int i = 0; i < failures; ++i) {
+                        ConcurrentUtil.backoff();
+                    }
+
+                    if (curr != (curr = this.compareAndExchangeReferenceCounter(curr, null))) {
+                        ++failures;
+                        continue;
+                    }
+
+                    // we have the reference count, we win no matter what.
+                    this.setPriorityVolatile(PrioritisedExecutor.Priority.COMPLETING);
+
+                    try {
+                        if (cancel) {
+                            this.cancelInternal();
+                        } else {
+                            this.executeInternal();
+                        }
+                    } finally {
+                        if (curr != REFERENCE_COUNTER_NOT_SET) {
+                            this.world.decrementReference(curr, this.sectionLowerLeftCoord);
+                        }
+                    }
+
+                    return true;
+                }
+            }
+
+            @Override
+            public boolean queue() {
+                if (this.getReferenceCounterVolatile() != REFERENCE_COUNTER_NOT_SET) {
+                    return false;
+                }
+
+                final AtomicLong referenceCounter = this.world.incrementReference(this.sectionLowerLeftCoord);
+                if (this.compareAndExchangeReferenceCounter(REFERENCE_COUNTER_NOT_SET, referenceCounter) != REFERENCE_COUNTER_NOT_SET) {
+                    // we don't expect race conditions here, so it is OK if we have to needlessly reference count
+                    this.world.decrementReference(referenceCounter, this.sectionLowerLeftCoord);
+                    return false;
+                }
+
+                boolean synchronise = false;
+                for (;;) {
+                    // we need to synchronise for repeated operations so that we guarantee that we do not retrieve
+                    // the same queue again, as the region lock will be given to us only when the merge/split operation
+                    // is done
+                    final PrioritisedQueue queue = this.world.getQueue(synchronise, this.chunkX, this.chunkZ, this.isChunkTask);
+
+                    if (queue == null) {
+                        if (!synchronise) {
+                            // may be incorrectly null when unsynchronised
+                            synchronise = true;
+                            continue;
+                        }
+                        // may have been cancelled before we got to the queue
+                        if (this.getReferenceCounterVolatile() != null) {
+                            throw new IllegalStateException("Expected null ref count when queue does not exist");
+                        }
+                        // the task never could be polled from the queue, so we return false
+                        // don't decrement reference count, as we were certainly cancelled by another thread, which
+                        // will decrement the reference count
+                        return false;
+                    }
+
+                    synchronise = true;
+
+                    final Boolean res = queue.tryPush(this);
+                    if (res == null) {
+                        // we were cancelled
+                        // don't decrement reference count, as we were certainly cancelled by another thread, which
+                        // will decrement the reference count
+                        return false;
+                    }
+
+                    if (!res.booleanValue()) {
+                        // failed, try again
+                        continue;
+                    }
+
+                    // successfully queued
+                    return true;
+                }
+            }
+
+            private AtomicLong trySetCompleting(final int minPriority) {
+                // first, try to set priority to EXECUTING
+                for (PrioritisedExecutor.Priority curr = this.getPriorityVolatile();;) {
+                    if (curr.isLowerPriority(minPriority)) {
+                        return null;
+                    }
+
+                    if (curr == (curr = this.compareAndExchangePriority(curr, PrioritisedExecutor.Priority.COMPLETING))) {
+                        break;
+                    } // else: continue
+                }
+
+                for (AtomicLong curr = this.getReferenceCounterVolatile();;) {
+                    if (curr == null) {
+                        // something acquired before us
+                        return null;
+                    }
+
+                    if (curr == REFERENCE_COUNTER_NOT_SET) {
+                        throw new IllegalStateException();
+                    }
+
+                    if (curr != (curr = this.compareAndExchangeReferenceCounter(curr, null))) {
+                        continue;
+                    }
+                    return curr;
+                }
+            }
+
+            private void updatePriorityInQueue() {
+                boolean synchronise = false;
+                for (;;) {
+                    final AtomicLong referenceCount = this.getReferenceCounterVolatile();
+                    if (referenceCount == REFERENCE_COUNTER_NOT_SET || referenceCount == null) {
+                        // cancelled or not queued
+                        return;
+                    }
+
+                    if (this.getPriorityVolatile() == PrioritisedExecutor.Priority.COMPLETING) {
+                        // cancelled
+                        return;
+                    }
+
+                    // we need to synchronise for repeated operations so that we guarantee that we do not retrieve
+                    // the same queue again, as the region lock will be given to us only when the merge/split operation
+                    // is done
+                    final PrioritisedQueue queue = this.world.getQueue(synchronise, this.chunkX, this.chunkZ, this.isChunkTask);
+
+                    if (queue == null) {
+                        if (!synchronise) {
+                            // may be incorrectly null when unsynchronised
+                            continue;
+                        }
+                        // must have been removed
+                        return;
+                    }
+
+                    synchronise = true;
+
+                    final Boolean res = queue.tryPush(this);
+                    if (res == null) {
+                        // we were cancelled
+                        return;
+                    }
+
+                    if (!res.booleanValue()) {
+                        // failed, try again
+                        continue;
+                    }
+
+                    // successfully queued
+                    return;
+                }
+            }
+
+            @Override
+            public PrioritisedExecutor.Priority getPriority() {
+                return this.getPriorityVolatile();
+            }
+
+            @Override
+            public boolean lowerPriority(final PrioritisedExecutor.Priority priority) {
+                int failures = 0;
+                for (PrioritisedExecutor.Priority curr = this.getPriorityVolatile();;) {
+                    if (curr == PrioritisedExecutor.Priority.COMPLETING) {
+                        return false;
+                    }
+
+                    if (curr.isLowerOrEqualPriority(priority)) {
+                        return false;
+                    }
+
+                    for (int i = 0; i < failures; ++i) {
+                        ConcurrentUtil.backoff();
+                    }
+
+                    if (curr == (curr = this.compareAndExchangePriority(curr, priority))) {
+                        this.updatePriorityInQueue();
+                        return true;
+                    }
+                    ++failures;
+                }
+            }
+
+            @Override
+            public boolean setPriority(final PrioritisedExecutor.Priority priority) {
+                int failures = 0;
+                for (PrioritisedExecutor.Priority curr = this.getPriorityVolatile();;) {
+                    if (curr == PrioritisedExecutor.Priority.COMPLETING) {
+                        return false;
+                    }
+
+                    if (curr == priority) {
+                        return false;
+                    }
+
+                    for (int i = 0; i < failures; ++i) {
+                        ConcurrentUtil.backoff();
+                    }
+
+                    if (curr == (curr = this.compareAndExchangePriority(curr, priority))) {
+                        this.updatePriorityInQueue();
+                        return true;
+                    }
+                    ++failures;
+                }
+            }
+
+            @Override
+            public boolean raisePriority(final PrioritisedExecutor.Priority priority) {
+                int failures = 0;
+                for (PrioritisedExecutor.Priority curr = this.getPriorityVolatile();;) {
+                    if (curr == PrioritisedExecutor.Priority.COMPLETING) {
+                        return false;
+                    }
+
+                    if (curr.isHigherOrEqualPriority(priority)) {
+                        return false;
+                    }
+
+                    for (int i = 0; i < failures; ++i) {
+                        ConcurrentUtil.backoff();
+                    }
+
+                    if (curr == (curr = this.compareAndExchangePriority(curr, priority))) {
+                        this.updatePriorityInQueue();
+                        return true;
+                    }
+                    ++failures;
+                }
+            }
+
+            @Override
+            public boolean execute() {
+                return this.tryComplete(false);
+            }
+
+            @Override
+            public boolean cancel() {
+                return this.tryComplete(true);
+            }
+        }
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/RegionizedWorldData.java b/src/main/java/io/papermc/paper/threadedregions/RegionizedWorldData.java
new file mode 100644
index 0000000000000000000000000000000000000000..e91df1496889b15041a297f243d7cfe7c78f1f6c
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionizedWorldData.java
@@ -0,0 +1,792 @@
+package io.papermc.paper.threadedregions;
+
+import com.destroystokyo.paper.util.maplist.ReferenceList;
+import com.destroystokyo.paper.util.misc.PlayerAreaMap;
+import com.destroystokyo.paper.util.misc.PooledLinkedHashSets;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.chunk.system.scheduling.ChunkHolderManager;
+import io.papermc.paper.util.CoordinateUtils;
+import io.papermc.paper.util.TickThread;
+import io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet;
+import io.papermc.paper.util.player.NearbyPlayers;
+import it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceMap;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
+import net.minecraft.CrashReport;
+import net.minecraft.ReportedException;
+import net.minecraft.core.BlockPos;
+import net.minecraft.network.Connection;
+import net.minecraft.network.PacketSendListener;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.MutableComponent;
+import net.minecraft.network.protocol.common.ClientboundDisconnectPacket;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import net.minecraft.util.VisibleForDebug;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.Mob;
+import net.minecraft.world.entity.ai.village.VillageSiege;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.level.BlockEventData;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Explosion;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.NaturalSpawner;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.RedStoneWireBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.entity.TickingBlockEntity;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.material.Fluid;
+import net.minecraft.world.level.redstone.CollectingNeighborUpdater;
+import net.minecraft.world.level.redstone.NeighborUpdater;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.ticks.LevelTicks;
+import org.bukkit.craftbukkit.block.CraftBlockState;
+import org.bukkit.craftbukkit.util.UnsafeList;
+import org.slf4j.Logger;
+import javax.annotation.Nullable;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+public final class RegionizedWorldData {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    public static final RegionizedData.RegioniserCallback<RegionizedWorldData> REGION_CALLBACK = new RegionizedData.RegioniserCallback<>() {
+        @Override
+        public void merge(final RegionizedWorldData from, final RegionizedWorldData into, final long fromTickOffset) {
+            // connections
+            for (final Connection conn : from.connections) {
+                into.connections.add(conn);
+            }
+            // time
+            final long fromRedstoneTimeOffset = into.redstoneTime - from.redstoneTime;
+            // entities
+            for (final ServerPlayer player : from.localPlayers) {
+                into.localPlayers.add(player);
+                into.nearbyPlayers.addPlayer(player);
+            }
+            for (final Entity entity : from.allEntities) {
+                into.allEntities.add(entity);
+                entity.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+            }
+            for (final Entity entity : from.loadedEntities) {
+                into.loadedEntities.add(entity);
+            }
+            for (final Entity entity : from.toProcessTrackingUnloading) {
+                into.toProcessTrackingUnloading.add(entity);
+            }
+            for (final Iterator<Entity> iterator = from.entityTickList.unsafeIterator(); iterator.hasNext();) {
+                into.entityTickList.add(iterator.next());
+            }
+            for (final Iterator<Mob> iterator = from.navigatingMobs.unsafeIterator(); iterator.hasNext();) {
+                into.navigatingMobs.add(iterator.next());
+            }
+            // block ticking
+            into.blockEvents.addAll(from.blockEvents);
+            // ticklists use game time
+            from.blockLevelTicks.merge(into.blockLevelTicks, fromRedstoneTimeOffset);
+            from.fluidLevelTicks.merge(into.fluidLevelTicks, fromRedstoneTimeOffset);
+
+            // tile entity ticking
+            for (final TickingBlockEntity tileEntityWrapped : from.pendingBlockEntityTickers) {
+                into.pendingBlockEntityTickers.add(tileEntityWrapped);
+                final BlockEntity tileEntity = tileEntityWrapped.getTileEntity();
+                if (tileEntity != null) {
+                    tileEntity.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+                }
+            }
+            for (final TickingBlockEntity tileEntityWrapped : from.blockEntityTickers) {
+                into.blockEntityTickers.add(tileEntityWrapped);
+                final BlockEntity tileEntity = tileEntityWrapped.getTileEntity();
+                if (tileEntity != null) {
+                    tileEntity.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+                }
+            }
+
+            // ticking chunks
+            for (final Iterator<LevelChunk> iterator = from.entityTickingChunks.unsafeIterator(); iterator.hasNext();) {
+                into.entityTickingChunks.add(iterator.next());
+            }
+            for (final Iterator<LevelChunk> iterator = from.tickingChunks.unsafeIterator(); iterator.hasNext();) {
+                into.tickingChunks.add(iterator.next());
+            }
+            // redstone torches
+            if (from.redstoneUpdateInfos != null && !from.redstoneUpdateInfos.isEmpty()) {
+                if (into.redstoneUpdateInfos == null) {
+                    into.redstoneUpdateInfos = new ArrayDeque<>();
+                }
+                for (final net.minecraft.world.level.block.RedstoneTorchBlock.Toggle info : from.redstoneUpdateInfos) {
+                    info.offsetTime(fromRedstoneTimeOffset);
+                    into.redstoneUpdateInfos.add(info);
+                }
+            }
+            // light chunks being worked on
+            into.chunksBeingWorkedOn.putAll(from.chunksBeingWorkedOn);
+            // mob spawning
+            into.catSpawnerNextTick = Math.max(from.catSpawnerNextTick, into.catSpawnerNextTick);
+            into.patrolSpawnerNextTick = Math.max(from.patrolSpawnerNextTick, into.patrolSpawnerNextTick);
+            into.phantomSpawnerNextTick = Math.max(from.phantomSpawnerNextTick, into.phantomSpawnerNextTick);
+            if (from.wanderingTraderTickDelay != Integer.MIN_VALUE && into.wanderingTraderTickDelay != Integer.MIN_VALUE) {
+                into.wanderingTraderTickDelay = Math.max(from.wanderingTraderTickDelay, into.wanderingTraderTickDelay);
+                into.wanderingTraderSpawnDelay = Math.max(from.wanderingTraderSpawnDelay, into.wanderingTraderSpawnDelay);
+                into.wanderingTraderSpawnChance = Math.max(from.wanderingTraderSpawnChance, into.wanderingTraderSpawnChance);
+            }
+        }
+
+        @Override
+        public void split(final RegionizedWorldData from, final int chunkToRegionShift,
+                          final Long2ReferenceOpenHashMap<RegionizedWorldData> regionToData,
+                          final ReferenceOpenHashSet<RegionizedWorldData> dataSet) {
+            // connections
+            for (final Connection conn : from.connections) {
+                final ServerPlayer player = conn.getPlayer();
+                final ChunkPos pos = player.chunkPosition();
+                // Note: It is impossible for an entity in the world to _not_ be in an entity chunk, which means
+                // the chunk holder must _exist_, and so the region section exists.
+                regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift))
+                    .connections.add(conn);
+            }
+            // entities
+            for (final ServerPlayer player : from.localPlayers) {
+                final ChunkPos pos = player.chunkPosition();
+                // Note: It is impossible for an entity in the world to _not_ be in an entity chunk, which means
+                // the chunk holder must _exist_, and so the region section exists.
+                final RegionizedWorldData into = regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift));
+                into.localPlayers.add(player);
+                into.nearbyPlayers.addPlayer(player);
+            }
+            for (final Entity entity : from.allEntities) {
+                final ChunkPos pos = entity.chunkPosition();
+                // Note: It is impossible for an entity in the world to _not_ be in an entity chunk, which means
+                // the chunk holder must _exist_, and so the region section exists.
+                final RegionizedWorldData into = regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift));
+                into.allEntities.add(entity);
+                // Note: entityTickList is a subset of allEntities
+                if (from.entityTickList.contains(entity)) {
+                    into.entityTickList.add(entity);
+                }
+                // Note: loadedEntities is a subset of allEntities
+                if (from.loadedEntities.contains(entity)) {
+                    into.loadedEntities.add(entity);
+                }
+                // Note: toProcessTrackingUnloading is not a subset of allEntities, but for the cases where it is not
+                // do not matter as the tracker removal is handled
+                if (from.toProcessTrackingUnloading.contains(entity)) {
+                    into.toProcessTrackingUnloading.add(entity);
+                }
+                // Note: navigatingMobs is a subset of allEntities
+                if (entity instanceof Mob mob && from.navigatingMobs.contains(mob)) {
+                    into.navigatingMobs.add(mob);
+                }
+            }
+            // block ticking
+            for (final BlockEventData blockEventData : from.blockEvents) {
+                final BlockPos pos = blockEventData.pos();
+                final int chunkX = pos.getX() >> 4;
+                final int chunkZ = pos.getZ() >> 4;
+
+                final RegionizedWorldData into = regionToData.get(CoordinateUtils.getChunkKey(chunkX >> chunkToRegionShift, chunkZ >> chunkToRegionShift));
+                // Unlike entities, the chunk holder is not guaranteed to exist for block events, because the block events
+                // is just some list. So if it unloads, I guess it's just lost.
+                if (into != null) {
+                    into.blockEvents.add(blockEventData);
+                }
+            }
+
+            final Long2ReferenceOpenHashMap<LevelTicks<Block>> levelTicksBlockRegionData = new Long2ReferenceOpenHashMap<>(regionToData.size(), 0.75f);
+            final Long2ReferenceOpenHashMap<LevelTicks<Fluid>> levelTicksFluidRegionData = new Long2ReferenceOpenHashMap<>(regionToData.size(), 0.75f);
+
+            for (final Iterator<Long2ReferenceMap.Entry<RegionizedWorldData>> iterator = regionToData.long2ReferenceEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Long2ReferenceMap.Entry<RegionizedWorldData> entry = iterator.next();
+                final long key = entry.getLongKey();
+                final RegionizedWorldData worldData = entry.getValue();
+
+                levelTicksBlockRegionData.put(key, worldData.blockLevelTicks);
+                levelTicksFluidRegionData.put(key, worldData.fluidLevelTicks);
+            }
+
+            from.blockLevelTicks.split(chunkToRegionShift, levelTicksBlockRegionData);
+            from.fluidLevelTicks.split(chunkToRegionShift, levelTicksFluidRegionData);
+
+            // tile entity ticking
+            for (final TickingBlockEntity tileEntity : from.pendingBlockEntityTickers) {
+                final BlockPos pos = tileEntity.getPos();
+                final int chunkX = pos.getX() >> 4;
+                final int chunkZ = pos.getZ() >> 4;
+
+                final RegionizedWorldData into = regionToData.get(CoordinateUtils.getChunkKey(chunkX >> chunkToRegionShift, chunkZ >> chunkToRegionShift));
+                if (into != null) {
+                    into.pendingBlockEntityTickers.add(tileEntity);
+                } // else: when a chunk unloads, it does not actually _remove_ the tile entity from the list, it just gets
+                  //       marked as removed. So if there is no section, it's probably removed!
+            }
+            for (final TickingBlockEntity tileEntity : from.blockEntityTickers) {
+                final BlockPos pos = tileEntity.getPos();
+                final int chunkX = pos.getX() >> 4;
+                final int chunkZ = pos.getZ() >> 4;
+
+                final RegionizedWorldData into = regionToData.get(CoordinateUtils.getChunkKey(chunkX >> chunkToRegionShift, chunkZ >> chunkToRegionShift));
+                if (into != null) {
+                    into.blockEntityTickers.add(tileEntity);
+                } // else: when a chunk unloads, it does not actually _remove_ the tile entity from the list, it just gets
+                  //       marked as removed. So if there is no section, it's probably removed!
+            }
+            // time
+            for (final RegionizedWorldData regionizedWorldData : dataSet) {
+                regionizedWorldData.redstoneTime = from.redstoneTime;
+            }
+            // ticking chunks
+            for (final Iterator<LevelChunk> iterator = from.entityTickingChunks.unsafeIterator(); iterator.hasNext();) {
+                final LevelChunk levelChunk = iterator.next();
+                final ChunkPos pos = levelChunk.getPos();
+
+                // Impossible for get() to return null, as the chunk is entity ticking - thus the chunk holder is loaded
+                regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift))
+                    .entityTickingChunks.add(levelChunk);
+            }
+            for (final Iterator<LevelChunk> iterator = from.tickingChunks.unsafeIterator(); iterator.hasNext();) {
+                final LevelChunk levelChunk = iterator.next();
+                final ChunkPos pos = levelChunk.getPos();
+
+                // Impossible for get() to return null, as the chunk is entity ticking - thus the chunk holder is loaded
+                regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift))
+                    .tickingChunks.add(levelChunk);
+            }
+            // redstone torches
+            if (from.redstoneUpdateInfos != null && !from.redstoneUpdateInfos.isEmpty()) {
+                for (final net.minecraft.world.level.block.RedstoneTorchBlock.Toggle info : from.redstoneUpdateInfos) {
+                    final BlockPos pos = info.pos;
+
+                    final RegionizedWorldData worldData = regionToData.get(CoordinateUtils.getChunkKey((pos.getX() >> 4) >> chunkToRegionShift, (pos.getZ() >> 4) >> chunkToRegionShift));
+                    if (worldData != null) {
+                        if (worldData.redstoneUpdateInfos == null) {
+                            worldData.redstoneUpdateInfos = new ArrayDeque<>();
+                        }
+                        worldData.redstoneUpdateInfos.add(info);
+                    } // else: chunk unloaded
+                }
+            }
+            // light chunks being worked on
+            for (final Iterator<Long2IntOpenHashMap.Entry> iterator = from.chunksBeingWorkedOn.long2IntEntrySet().fastIterator(); iterator.hasNext();) {
+                final Long2IntOpenHashMap.Entry entry = iterator.next();
+                final long pos = entry.getLongKey();
+                final int chunkX = CoordinateUtils.getChunkX(pos);
+                final int chunkZ = CoordinateUtils.getChunkZ(pos);
+                final int value = entry.getIntValue();
+
+                // should never be null, as it is a reference counter for ticket
+                regionToData.get(CoordinateUtils.getChunkKey(chunkX >> chunkToRegionShift, chunkZ >> chunkToRegionShift)).chunksBeingWorkedOn.put(pos, value);
+            }
+            // mob spawning
+            for (final RegionizedWorldData regionizedWorldData : dataSet) {
+                regionizedWorldData.catSpawnerNextTick = from.catSpawnerNextTick;
+                regionizedWorldData.patrolSpawnerNextTick = from.patrolSpawnerNextTick;
+                regionizedWorldData.phantomSpawnerNextTick = from.phantomSpawnerNextTick;
+                regionizedWorldData.wanderingTraderTickDelay = from.wanderingTraderTickDelay;
+                regionizedWorldData.wanderingTraderSpawnChance = from.wanderingTraderSpawnChance;
+                regionizedWorldData.wanderingTraderSpawnDelay = from.wanderingTraderSpawnDelay;
+                regionizedWorldData.villageSiegeState = new VillageSiegeState(); // just re set it, as the spawn pos will be invalid
+            }
+        }
+    };
+
+    public final ServerLevel world;
+
+    private RegionizedServer.WorldLevelData tickData;
+
+    // connections
+    public final List<Connection> connections = new ArrayList<>();
+
+    // misc. fields
+    private boolean isHandlingTick;
+
+    public void setHandlingTick(final boolean to) {
+        this.isHandlingTick = to;
+    }
+
+    public boolean isHandlingTick() {
+        return this.isHandlingTick;
+    }
+
+    // entities
+    private final List<ServerPlayer> localPlayers = new ArrayList<>();
+    private final NearbyPlayers nearbyPlayers;
+    private final ReferenceList<Entity> allEntities = new ReferenceList<>();
+    private final ReferenceList<Entity> loadedEntities = new ReferenceList<>();
+    private final ReferenceList<Entity> toProcessTrackingUnloading = new ReferenceList<>();
+    private final IteratorSafeOrderedReferenceSet<Entity> entityTickList = new IteratorSafeOrderedReferenceSet<>();
+    private final IteratorSafeOrderedReferenceSet<Mob> navigatingMobs = new IteratorSafeOrderedReferenceSet<>();
+
+    // block ticking
+    private final ObjectLinkedOpenHashSet<BlockEventData> blockEvents = new ObjectLinkedOpenHashSet<>();
+    private final LevelTicks<Block> blockLevelTicks;
+    private final LevelTicks<Fluid> fluidLevelTicks;
+
+    // tile entity ticking
+    private final List<TickingBlockEntity> pendingBlockEntityTickers = new ArrayList<>();
+    private final List<TickingBlockEntity> blockEntityTickers = new ArrayList<>();
+    private boolean tickingBlockEntities;
+
+    // time
+    private long redstoneTime = 1L;
+
+    public long getRedstoneGameTime() {
+        return this.redstoneTime;
+    }
+
+    public void setRedstoneGameTime(final long to) {
+        this.redstoneTime = to;
+    }
+
+    // ticking chunks
+    private final IteratorSafeOrderedReferenceSet<LevelChunk> entityTickingChunks = new IteratorSafeOrderedReferenceSet<>();
+    private final IteratorSafeOrderedReferenceSet<LevelChunk> tickingChunks = new IteratorSafeOrderedReferenceSet<>();
+    private final IteratorSafeOrderedReferenceSet<LevelChunk> chunks = new IteratorSafeOrderedReferenceSet<>();
+
+    // Paper/CB api hook misc
+    // don't bother to merge/split these, no point
+    // From ServerLevel
+    public boolean hasPhysicsEvent = true; // Paper
+    public boolean hasEntityMoveEvent = false; // Paper
+    // Paper start - Optimize Hoppers
+    public boolean skipPullModeEventFire = false;
+    public boolean skipPushModeEventFire = false;
+    public boolean skipHopperEvents = false;
+    // Paper end - Optimize Hoppers
+    public long lastMidTickExecuteFailure;
+    public long lastMidTickExecute;
+    // From Level
+    public boolean populating;
+    public final NeighborUpdater neighborUpdater;
+    public boolean preventPoiUpdated = false; // CraftBukkit - SPIGOT-5710
+    public boolean captureBlockStates = false;
+    public boolean captureTreeGeneration = false;
+    public final Map<BlockPos, CraftBlockState> capturedBlockStates = new java.util.LinkedHashMap<>(); // Paper
+    public final Map<BlockPos, BlockEntity> capturedTileEntities = new java.util.LinkedHashMap<>(); // Paper
+    public List<ItemEntity> captureDrops;
+    // Paper start
+    public int wakeupInactiveRemainingAnimals;
+    public int wakeupInactiveRemainingFlying;
+    public int wakeupInactiveRemainingMonsters;
+    public int wakeupInactiveRemainingVillagers;
+    // Paper end
+    public final TempCollisionList<AABB> tempCollisionList = new TempCollisionList<>();
+    public final TempCollisionList<Entity> tempEntitiesList = new TempCollisionList<>();
+    public int currentPrimedTnt = 0; // Spigot
+    @Nullable
+    @VisibleForDebug
+    public NaturalSpawner.SpawnState lastSpawnState;
+    public boolean shouldSignal = true;
+    public final Map<Explosion.CacheKey, Float> explosionDensityCache = new HashMap<>(64, 0.25f);
+
+    // not transient
+    public java.util.ArrayDeque<net.minecraft.world.level.block.RedstoneTorchBlock.Toggle> redstoneUpdateInfos;
+    public final Long2IntOpenHashMap chunksBeingWorkedOn = new Long2IntOpenHashMap();
+
+    public static final class TempCollisionList<T> {
+        final UnsafeList<T> list = new UnsafeList<>(64);
+        boolean inUse;
+
+        public UnsafeList<T> get() {
+            if (this.inUse) {
+                return new UnsafeList<>(16);
+            }
+            this.inUse = true;
+            return this.list;
+        }
+
+        public void ret(List<T> list) {
+            if (list != this.list) {
+                return;
+            }
+
+            ((UnsafeList)list).setSize(0);
+            this.inUse = false;
+        }
+
+        public void reset() {
+            this.list.completeReset();
+        }
+    }
+    public void resetCollisionLists() {
+        this.tempCollisionList.reset();
+        this.tempEntitiesList.reset();
+    }
+
+    // Mob spawning
+    private final PooledLinkedHashSets<ServerPlayer> pooledHashSets = new PooledLinkedHashSets<>();
+    public final PlayerAreaMap mobSpawnMap = new PlayerAreaMap(this.pooledHashSets);
+    public int catSpawnerNextTick = 0;
+    public int patrolSpawnerNextTick = 0;
+    public int phantomSpawnerNextTick = 0;
+    public int wanderingTraderTickDelay = Integer.MIN_VALUE;
+    public int wanderingTraderSpawnDelay;
+    public int wanderingTraderSpawnChance;
+    public VillageSiegeState villageSiegeState = new VillageSiegeState();
+
+    public static final class VillageSiegeState {
+        public boolean hasSetupSiege;
+        public VillageSiege.State siegeState = VillageSiege.State.SIEGE_DONE;
+        public int zombiesToSpawn;
+        public int nextSpawnTime;
+        public int spawnX;
+        public int spawnY;
+        public int spawnZ;
+    }
+    // Redstone
+    public final alternate.current.wire.WireHandler wireHandler;
+    public final com.destroystokyo.paper.util.RedstoneWireTurbo turbo;
+
+    public RegionizedWorldData(final ServerLevel world) {
+        this.world = world;
+        this.blockLevelTicks = new LevelTicks<>(world::isPositionTickingWithEntitiesLoaded, world.getProfilerSupplier(), world, true);
+        this.fluidLevelTicks = new LevelTicks<>(world::isPositionTickingWithEntitiesLoaded, world.getProfilerSupplier(), world, false);
+        this.neighborUpdater = new CollectingNeighborUpdater(world, world.neighbourUpdateMax);
+        this.nearbyPlayers = new NearbyPlayers(world);
+        this.wireHandler = new alternate.current.wire.WireHandler(world);
+        this.turbo = new com.destroystokyo.paper.util.RedstoneWireTurbo((RedStoneWireBlock)Blocks.REDSTONE_WIRE);
+
+        // tasks may be drained before the region ticks, so we must set up the tick data early just in case
+        this.updateTickData();
+    }
+
+    public void checkWorld(final Level against) {
+        if (this.world != against) {
+            throw new IllegalStateException("World mismatch: expected " + this.world.getWorld().getName() + " but got " + (against == null ? "null" : against.getWorld().getName()));
+        }
+    }
+
+    public RegionizedServer.WorldLevelData getTickData() {
+        return this.tickData;
+    }
+
+    private long lagCompensationTick;
+
+    public long getLagCompensationTick() {
+        return this.lagCompensationTick;
+    }
+
+    public void updateTickData() {
+        this.tickData = this.world.tickData;
+        this.hasPhysicsEvent = org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper
+        this.hasEntityMoveEvent = io.papermc.paper.event.entity.EntityMoveEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper
+        this.skipHopperEvents = this.world.paperConfig().hopper.disableMoveEvent || org.bukkit.event.inventory.InventoryMoveItemEvent.getHandlerList().getRegisteredListeners().length == 0; // Paper
+        // always subtract from server init so that the tick starts at zero, allowing us to cast to int without much worry
+        this.lagCompensationTick = (System.nanoTime() - MinecraftServer.SERVER_INIT) / TickRegionScheduler.TIME_BETWEEN_TICKS;
+    }
+
+    public NearbyPlayers getNearbyPlayers() {
+        return this.nearbyPlayers;
+    }
+
+    private static void cleanUpConnection(final Connection conn) {
+        // note: ALL connections HERE have a player
+        final ServerPlayer player = conn.getPlayer();
+        // now that the connection is removed, we can allow this region to die
+        player.serverLevel().chunkSource.removeTicketAtLevel(
+            ServerGamePacketListenerImpl.DISCONNECT_TICKET, player.connection.disconnectPos,
+            ChunkHolderManager.MAX_TICKET_LEVEL,
+            player.connection.disconnectTicketId
+        );
+    }
+
+    // connections
+    public void tickConnections() {
+        final List<Connection> connections = new ArrayList<>(this.connections);
+        Collections.shuffle(connections);
+        for (final Connection conn : connections) {
+            if (!conn.isConnected()) {
+                conn.handleDisconnection();
+                // global tick thread will not remove connections not owned by it, so we need to
+                RegionizedServer.getInstance().removeConnection(conn);
+                this.connections.remove(conn);
+                cleanUpConnection(conn);
+                continue;
+            }
+            if (!this.connections.contains(conn)) {
+                // removed by connection tick?
+                continue;
+            }
+
+            try {
+                conn.tick();
+            } catch (final Exception exception) {
+                if (conn.isMemoryConnection()) {
+                    throw new ReportedException(CrashReport.forThrowable(exception, "Ticking memory connection"));
+                }
+
+                LOGGER.warn("Failed to handle packet for {}", conn.getLoggableAddress(MinecraftServer.getServer().logIPs()), exception);
+                MutableComponent ichatmutablecomponent = Component.literal("Internal server error");
+
+                conn.send(new ClientboundDisconnectPacket(ichatmutablecomponent), PacketSendListener.thenRun(() -> {
+                    conn.disconnect(ichatmutablecomponent);
+                }));
+                conn.setReadOnly();
+                continue;
+            }
+        }
+    }
+
+    // entities hooks
+    public int getEntityCount() {
+        return this.allEntities.size();
+    }
+
+    public int getPlayerCount() {
+        return this.localPlayers.size();
+    }
+
+    public Iterable<Entity> getLocalEntities() {
+        return this.allEntities;
+    }
+
+    public Entity[] getLocalEntitiesCopy() {
+        return Arrays.copyOf(this.allEntities.getRawData(), this.allEntities.size(), Entity[].class);
+    }
+
+    public List<ServerPlayer> getLocalPlayers() {
+        return this.localPlayers;
+    }
+
+    public void addLoadedEntity(final Entity entity) {
+        if (this.loadedEntities.add(entity)) {
+            this.toProcessTrackingUnloading.remove(entity);
+        }
+    }
+
+    public boolean hasLoadedEntity(final Entity entity) {
+        return this.loadedEntities.contains(entity);
+    }
+
+    public void removeLoadedEntity(final Entity entity) {
+        if (this.loadedEntities.remove(entity)) {
+            this.toProcessTrackingUnloading.add(entity);
+        }
+    }
+
+    public Iterable<Entity> getLoadedEntities() {
+        return this.loadedEntities;
+    }
+
+    public Entity[] takeTrackingUnloads() {
+        final Entity[] ret = Arrays.copyOf(this.toProcessTrackingUnloading.getRawData(), this.toProcessTrackingUnloading.size(), Entity[].class);
+
+        this.toProcessTrackingUnloading.clear();
+
+        return ret;
+    }
+
+    public void addEntityTickingEntity(final Entity entity) {
+        if (!TickThread.isTickThreadFor(entity)) {
+            throw new IllegalArgumentException("Entity " + entity + " is not under this region's control");
+        }
+        this.entityTickList.add(entity);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public boolean hasEntityTickingEntity(final Entity entity) {
+        return this.entityTickList.contains(entity);
+    }
+
+    public void removeEntityTickingEntity(final Entity entity) {
+        if (!TickThread.isTickThreadFor(entity)) {
+            throw new IllegalArgumentException("Entity " + entity + " is not under this region's control");
+        }
+        this.entityTickList.remove(entity);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public void forEachTickingEntity(final Consumer<Entity> action) {
+        final IteratorSafeOrderedReferenceSet.Iterator<Entity> iterator = this.entityTickList.iterator();
+        try {
+            while (iterator.hasNext()) {
+                action.accept(iterator.next());
+            }
+        } finally {
+            iterator.finishedIterating();
+        }
+    }
+
+    public void addEntity(final Entity entity) {
+        if (!TickThread.isTickThreadFor(this.world, entity.chunkPosition())) {
+            throw new IllegalArgumentException("Entity " + entity + " is not under this region's control");
+        }
+        if (this.allEntities.add(entity)) {
+            if (entity instanceof ServerPlayer player) {
+                this.localPlayers.add(player);
+                this.nearbyPlayers.addPlayer(player);
+            }
+            TickRegions.RegionStats.updateCurrentRegion();
+        }
+    }
+
+    public boolean hasEntity(final Entity entity) {
+        return this.allEntities.contains(entity);
+    }
+
+    public void removeEntity(final Entity entity) {
+        if (!TickThread.isTickThreadFor(entity)) {
+            throw new IllegalArgumentException("Entity " + entity + " is not under this region's control");
+        }
+        if (this.allEntities.remove(entity)) {
+            if (entity instanceof ServerPlayer player) {
+                this.localPlayers.remove(player);
+                this.nearbyPlayers.removePlayer(player);
+            }
+            TickRegions.RegionStats.updateCurrentRegion();
+        }
+    }
+
+    public void addNavigatingMob(final Mob mob) {
+        if (!TickThread.isTickThreadFor(mob)) {
+            throw new IllegalArgumentException("Entity " + mob + " is not under this region's control");
+        }
+        this.navigatingMobs.add(mob);
+    }
+
+    public void removeNavigatingMob(final Mob mob) {
+        if (!TickThread.isTickThreadFor(mob)) {
+            throw new IllegalArgumentException("Entity " + mob + " is not under this region's control");
+        }
+        this.navigatingMobs.remove(mob);
+    }
+
+    public Iterator<Mob> getNavigatingMobs() {
+        return this.navigatingMobs.unsafeIterator();
+    }
+
+    // block ticking hooks
+    // Since block event data does not require chunk holders to be created for the chunk they reside in,
+    // it's not actually guaranteed that when merging / splitting data that we actually own the data...
+    // Note that we can only ever not own the event data when the chunk unloads, and so I've decided to
+    // make the code easier by simply discarding it in such an event
+    public void pushBlockEvent(final BlockEventData blockEventData) {
+        TickThread.ensureTickThread(this.world, blockEventData.pos(), "Cannot queue block even data async");
+        this.blockEvents.add(blockEventData);
+    }
+
+    public void pushBlockEvents(final Collection<? extends BlockEventData> blockEvents) {
+        for (final BlockEventData blockEventData : blockEvents) {
+            this.pushBlockEvent(blockEventData);
+        }
+    }
+
+    public void removeIfBlockEvents(final Predicate<? super BlockEventData> predicate) {
+        for (final Iterator<BlockEventData> iterator = this.blockEvents.iterator(); iterator.hasNext();) {
+            final BlockEventData blockEventData = iterator.next();
+            if (predicate.test(blockEventData)) {
+                iterator.remove();
+            }
+        }
+    }
+
+    public BlockEventData removeFirstBlockEvent() {
+        BlockEventData ret;
+        while (!this.blockEvents.isEmpty()) {
+            ret = this.blockEvents.removeFirst();
+            if (TickThread.isTickThreadFor(this.world, ret.pos())) {
+                return ret;
+            } // else: chunk must have been unloaded
+        }
+
+        return null;
+    }
+
+    public LevelTicks<Block> getBlockLevelTicks() {
+        return this.blockLevelTicks;
+    }
+
+    public LevelTicks<Fluid> getFluidLevelTicks() {
+        return this.fluidLevelTicks;
+    }
+
+    // tile entity ticking
+    public void addBlockEntityTicker(final TickingBlockEntity ticker) {
+        TickThread.ensureTickThread(this.world, ticker.getPos(), "Tile entity must be owned by current region");
+
+        (this.tickingBlockEntities ? this.pendingBlockEntityTickers : this.blockEntityTickers).add(ticker);
+    }
+
+    public void seTtickingBlockEntities(final boolean to) {
+        this.tickingBlockEntities = true;
+    }
+
+    public List<TickingBlockEntity> getBlockEntityTickers() {
+        return this.blockEntityTickers;
+    }
+
+    public void pushPendingTickingBlockEntities() {
+        if (!this.pendingBlockEntityTickers.isEmpty()) {
+            this.blockEntityTickers.addAll(this.pendingBlockEntityTickers);
+            this.pendingBlockEntityTickers.clear();
+        }
+    }
+
+    // ticking chunks
+    public void addEntityTickingChunk(final LevelChunk levelChunk) {
+        this.entityTickingChunks.add(levelChunk);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public void removeEntityTickingChunk(final LevelChunk levelChunk) {
+        this.entityTickingChunks.remove(levelChunk);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public IteratorSafeOrderedReferenceSet<LevelChunk> getEntityTickingChunks() {
+        return this.entityTickingChunks;
+    }
+
+    public void addTickingChunk(final LevelChunk levelChunk) {
+        this.tickingChunks.add(levelChunk);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public void removeTickingChunk(final LevelChunk levelChunk) {
+        this.tickingChunks.remove(levelChunk);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public IteratorSafeOrderedReferenceSet<LevelChunk> getTickingChunks() {
+        return this.tickingChunks;
+    }
+
+    public void addChunk(final LevelChunk levelChunk) {
+        this.chunks.add(levelChunk);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public void removeChunk(final LevelChunk levelChunk) {
+        this.chunks.remove(levelChunk);
+        TickRegions.RegionStats.updateCurrentRegion();
+    }
+
+    public IteratorSafeOrderedReferenceSet<LevelChunk> getChunks() {
+        return this.chunks;
+    }
+
+    public int getEntityTickingChunkCount() {
+        return this.entityTickingChunks.size();
+    }
+
+    public int getChunkCount() {
+        return this.chunks.size();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/Schedule.java b/src/main/java/io/papermc/paper/threadedregions/Schedule.java
new file mode 100644
index 0000000000000000000000000000000000000000..112d24a93bddf3d81c9176c05340c94ecd1a40a3
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/Schedule.java
@@ -0,0 +1,91 @@
+package io.papermc.paper.threadedregions;
+
+/**
+ * A Schedule is an object that can be used to maintain a periodic schedule for an event of interest.
+ */
+public final class Schedule {
+
+    private long lastPeriod;
+
+    /**
+     * Initialises a schedule with the provided period.
+     * @param firstPeriod The last time an event of interest occurred.
+     * @see #setLastPeriod(long)
+     */
+    public Schedule(final long firstPeriod) {
+        this.lastPeriod = firstPeriod;
+    }
+
+    /**
+     * Updates the last period to the specified value. This call sets the last "time" the event
+     * of interest took place at. Thus, the value returned by {@link #getDeadline(long)} is
+     * the provided time plus the period length provided to {@code getDeadline}.
+     * @param value The value to set the last period to.
+     */
+    public void setLastPeriod(final long value) {
+        this.lastPeriod = value;
+    }
+
+    /**
+     * Returns the last time the event of interest should have taken place.
+     */
+    public long getLastPeriod() {
+        return this.lastPeriod;
+    }
+
+    /**
+     * Returns the number of times the event of interest should have taken place between the last
+     * period and the provided time given the period between each event.
+     * @param periodLength The length of the period between events in ns.
+     * @param time The provided time.
+     */
+    public int getPeriodsAhead(final long periodLength, final long time) {
+        final long difference = time - this.lastPeriod;
+        final int ret = (int)(Math.abs(difference) / periodLength);
+        return difference >= 0 ? ret : -ret;
+    }
+
+    /**
+     * Returns the next starting deadline for the event of interest to take place,
+     * given the provided period length.
+     * @param periodLength The provided period length.
+     */
+    public long getDeadline(final long periodLength) {
+        return this.lastPeriod + periodLength;
+    }
+
+    /**
+     * Adjusts the last period so that the next starting deadline returned is the next period specified,
+     * given the provided period length.
+     * @param nextPeriod The specified next starting deadline.
+     * @param periodLength The specified period length.
+     */
+    public void setNextPeriod(final long nextPeriod, final long periodLength) {
+        this.lastPeriod = nextPeriod - periodLength;
+    }
+
+    /**
+     * Increases the last period by the specified number of periods and period length.
+     * The specified number of periods may be < 0, in which case the last period
+     * will decrease.
+     * @param periods The specified number of periods.
+     * @param periodLength The specified period length.
+     */
+    public void advanceBy(final int periods, final long periodLength) {
+        this.lastPeriod += (long)periods * periodLength;
+    }
+
+    /**
+     * Sets the last period so that it is the specified number of periods ahead
+     * given the specified time and period length.
+     * @param periodsToBeAhead Specified number of periods to be ahead by.
+     * @param periodLength The specified period length.
+     * @param time The specified time.
+     */
+    public void setPeriodsAhead(final int periodsToBeAhead, final long periodLength, final long time) {
+        final int periodsAhead = this.getPeriodsAhead(periodLength, time);
+        final int periodsToAdd = periodsToBeAhead - periodsAhead;
+
+        this.lastPeriod -= (long)periodsToAdd * periodLength;
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/TeleportUtils.java b/src/main/java/io/papermc/paper/threadedregions/TeleportUtils.java
new file mode 100644
index 0000000000000000000000000000000000000000..7b31c4ea6d01f936271bdadc3626201dcf32a683
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/TeleportUtils.java
@@ -0,0 +1,70 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.completable.Completable;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.phys.Vec3;
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.event.player.PlayerTeleportEvent;
+import java.util.function.Consumer;
+
+public final class TeleportUtils {
+
+    public static void teleport(final Entity from, final boolean useFromRootVehicle, final Entity to, final Float yaw, final Float pitch,
+                                final long teleportFlags, final PlayerTeleportEvent.TeleportCause cause, final Consumer<Entity> onComplete) {
+        // retrieve coordinates
+        final Completable<Location> positionCompletable = new Completable<>();
+
+        positionCompletable.addWaiter(
+            (final Location loc, final Throwable thr) -> {
+                if (loc == null) {
+                    if (onComplete != null) {
+                        onComplete.accept(null);
+                    }
+                    return;
+                }
+                final boolean scheduled = from.getBukkitEntity().taskScheduler.schedule(
+                    (final Entity realFrom) -> {
+                        final Vec3 pos = new Vec3(
+                            loc.getX(), loc.getY(), loc.getZ()
+                        );
+                        (useFromRootVehicle ? realFrom.getRootVehicle() : realFrom).teleportAsync(
+                            ((CraftWorld)loc.getWorld()).getHandle(), pos, null, null, null,
+                            cause, teleportFlags, onComplete
+                        );
+                    },
+                    (final Entity retired) -> {
+                        if (onComplete != null) {
+                            onComplete.accept(null);
+                        }
+                    },
+                    1L
+                );
+                if (!scheduled) {
+                    if (onComplete != null) {
+                        onComplete.accept(null);
+                    }
+                }
+            }
+        );
+
+        final boolean scheduled = to.getBukkitEntity().taskScheduler.schedule(
+            (final Entity target) -> {
+                positionCompletable.complete(target.getBukkitEntity().getLocation());
+            },
+            (final Entity retired) -> {
+                if (onComplete != null) {
+                    onComplete.accept(null);
+                }
+            },
+            1L
+        );
+        if (!scheduled) {
+            if (onComplete != null) {
+                onComplete.accept(null);
+            }
+        }
+    }
+
+    private TeleportUtils() {}
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/ThreadedRegionizer.java b/src/main/java/io/papermc/paper/threadedregions/ThreadedRegionizer.java
new file mode 100644
index 0000000000000000000000000000000000000000..531aa50f2c84e13358e8918bb0c15ea3cd036cb5
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/ThreadedRegionizer.java
@@ -0,0 +1,1405 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable;
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import com.destroystokyo.paper.util.SneakyThrow;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.util.CoordinateUtils;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.longs.LongArrayList;
+import it.unimi.dsi.fastutil.longs.LongComparator;
+import it.unimi.dsi.fastutil.longs.LongIterator;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.ChunkPos;
+import org.slf4j.Logger;
+import java.lang.invoke.VarHandle;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.StampedLock;
+import java.util.function.BooleanSupplier;
+import java.util.function.Consumer;
+
+public final class ThreadedRegionizer<R extends ThreadedRegionizer.ThreadedRegionData<R, S>, S extends ThreadedRegionizer.ThreadedRegionSectionData> {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    public final int regionSectionChunkSize;
+    public final int sectionChunkShift;
+    public final int minSectionRecalcCount;
+    public final int emptySectionCreateRadius;
+    public final int regionSectionMergeRadius;
+    public final double maxDeadRegionPercent;
+    public final ServerLevel world;
+
+    private final SWMRLong2ObjectHashTable<ThreadedRegionSection<R, S>> sections = new SWMRLong2ObjectHashTable<>();
+    private final SWMRLong2ObjectHashTable<ThreadedRegion<R, S>> regionsById = new SWMRLong2ObjectHashTable<>();
+    private final RegionCallbacks<R, S> callbacks;
+    private final StampedLock regionLock = new StampedLock();
+    private Thread writeLockOwner;
+
+    /*
+    static final record Operation(String type, int chunkX, int chunkZ) {}
+    private final MultiThreadedQueue<Operation> ops = new MultiThreadedQueue<>();
+     */
+
+    /*
+     * See REGION_LOGIC.md for complete details on what this class is doing
+     */
+
+    public ThreadedRegionizer(final int minSectionRecalcCount, final double maxDeadRegionPercent,
+                              final int emptySectionCreateRadius, final int regionSectionMergeRadius,
+                              final int regionSectionChunkShift, final ServerLevel world,
+                              final RegionCallbacks<R, S> callbacks) {
+        if (emptySectionCreateRadius <= 0) {
+            throw new IllegalStateException("Region section create radius must be > 0");
+        }
+        if (regionSectionMergeRadius <= 0) {
+            throw new IllegalStateException("Region section merge radius must be > 0");
+        }
+        this.regionSectionChunkSize = 1 << regionSectionChunkShift;
+        this.sectionChunkShift = regionSectionChunkShift;
+        this.minSectionRecalcCount = Math.max(2, minSectionRecalcCount);
+        this.maxDeadRegionPercent = maxDeadRegionPercent;
+        this.emptySectionCreateRadius = emptySectionCreateRadius;
+        this.regionSectionMergeRadius = regionSectionMergeRadius;
+        this.world = world;
+        this.callbacks = callbacks;
+        //this.loadTestData();
+    }
+
+    /*
+    private static String substr(String val, String prefix, int from) {
+        int idx = val.indexOf(prefix, from) + prefix.length();
+        int idx2 = val.indexOf(',', idx);
+        if (idx2 == -1) {
+            idx2 = val.indexOf(']', idx);
+        }
+        return val.substring(idx, idx2);
+    }
+
+    private void loadTestData() {
+        if (true) {
+            return;
+        }
+        try {
+            final JsonArray arr = JsonParser.parseReader(new FileReader("test.json")).getAsJsonArray();
+
+            List<Operation> ops = new ArrayList<>();
+
+            for (JsonElement elem : arr) {
+                JsonObject obj = elem.getAsJsonObject();
+                String val = obj.get("value").getAsString();
+
+                String type = substr(val, "type=", 0);
+                String x = substr(val, "chunkX=", 0);
+                String z = substr(val, "chunkZ=", 0);
+
+                ops.add(new Operation(type, Integer.parseInt(x), Integer.parseInt(z)));
+            }
+
+            for (Operation op : ops) {
+                switch (op.type) {
+                    case "add": {
+                        this.addChunk(op.chunkX, op.chunkZ);
+                        break;
+                    }
+                    case "remove": {
+                        this.removeChunk(op.chunkX, op.chunkZ);
+                        break;
+                    }
+                    case "mark_ticking": {
+                        this.sections.get(CoordinateUtils.getChunkKey(op.chunkX, op.chunkZ)).region.tryMarkTicking();
+                        break;
+                    }
+                    case "rel_region": {
+                        if (this.sections.get(CoordinateUtils.getChunkKey(op.chunkX, op.chunkZ)).region.state == ThreadedRegion.STATE_TICKING) {
+                            this.sections.get(CoordinateUtils.getChunkKey(op.chunkX, op.chunkZ)).region.markNotTicking();
+                        }
+                        break;
+                    }
+                }
+            }
+
+        } catch (final Exception ex) {
+            throw new IllegalStateException(ex);
+        }
+    }
+     */
+
+    public void acquireReadLock() {
+        this.regionLock.readLock();
+    }
+
+    public void releaseReadLock() {
+        this.regionLock.tryUnlockRead();
+    }
+
+    private void acquireWriteLock() {
+        final Thread currentThread = Thread.currentThread();
+        if (this.writeLockOwner == currentThread) {
+            throw new IllegalStateException("Cannot recursively operate in the regioniser");
+        }
+        this.regionLock.writeLock();
+        this.writeLockOwner = currentThread;
+    }
+
+    private void releaseWriteLock() {
+        this.writeLockOwner = null;
+        this.regionLock.tryUnlockWrite();
+    }
+
+    private void onRegionCreate(final ThreadedRegion<R, S> region) {
+        final ThreadedRegion<R, S> conflict;
+        if ((conflict = this.regionsById.putIfAbsent(region.id, region)) != null) {
+            throw new IllegalStateException("Region " + region + " is already mapped to " + conflict);
+        }
+    }
+
+    private void onRegionDestroy(final ThreadedRegion<R, S> region) {
+        final ThreadedRegion<R, S> removed = this.regionsById.remove(region.id);
+        if (removed != region) {
+            throw new IllegalStateException("Expected to remove " + region + ", but removed " + removed);
+        }
+    }
+
+    public int getSectionCoordinate(final int chunkCoordinate) {
+        return chunkCoordinate >> this.sectionChunkShift;
+    }
+
+    public long getSectionKey(final BlockPos pos) {
+        return CoordinateUtils.getChunkKey((pos.getX() >> 4) >> this.sectionChunkShift, (pos.getZ() >> 4) >> this.sectionChunkShift);
+    }
+
+    public long getSectionKey(final ChunkPos pos) {
+        return CoordinateUtils.getChunkKey(pos.x >> this.sectionChunkShift, pos.z >> this.sectionChunkShift);
+    }
+
+    public long getSectionKey(final Entity entity) {
+        final ChunkPos pos = entity.chunkPosition();
+        return CoordinateUtils.getChunkKey(pos.x >> this.sectionChunkShift, pos.z >> this.sectionChunkShift);
+    }
+
+    public void computeForAllRegions(final Consumer<? super ThreadedRegion<R, S>> consumer) {
+        this.regionLock.readLock();
+        try {
+            this.regionsById.forEachValue(consumer);
+        } finally {
+            this.regionLock.tryUnlockRead();
+        }
+    }
+
+    public void computeForAllRegionsUnsynchronised(final Consumer<? super ThreadedRegion<R, S>> consumer) {
+        this.regionsById.forEachValue(consumer);
+    }
+
+    public int computeForRegions(final int fromChunkX, final int fromChunkZ, final int toChunkX, final int toChunkZ,
+                                  final Consumer<Set<ThreadedRegion<R, S>>> consumer) {
+        final int shift = this.sectionChunkShift;
+        final int fromSectionX = fromChunkX >> shift;
+        final int fromSectionZ = fromChunkZ >> shift;
+        final int toSectionX = toChunkX >> shift;
+        final int toSectionZ = toChunkZ >> shift;
+        this.acquireWriteLock();
+        try {
+            final ReferenceOpenHashSet<ThreadedRegion<R, S>> set = new ReferenceOpenHashSet<>();
+
+            for (int currZ = fromSectionZ; currZ <= toSectionZ; ++currZ) {
+                for (int currX = fromSectionX; currX <= toSectionX; ++currX) {
+                    final ThreadedRegionSection<R, S> section = this.sections.get(CoordinateUtils.getChunkKey(currX, currZ));
+                    if (section != null) {
+                        set.add(section.getRegionPlain());
+                    }
+                }
+            }
+
+            consumer.accept(set);
+
+            return set.size();
+        } finally {
+            this.releaseWriteLock();
+        }
+    }
+
+    public ThreadedRegion<R, S> getRegionAtUnsynchronised(final int chunkX, final int chunkZ) {
+        final int sectionX = chunkX >> this.sectionChunkShift;
+        final int sectionZ = chunkZ >> this.sectionChunkShift;
+        final long sectionKey = CoordinateUtils.getChunkKey(sectionX, sectionZ);
+
+        final ThreadedRegionSection<R, S> section = this.sections.get(sectionKey);
+
+        return section == null ? null : section.getRegion();
+    }
+
+    public ThreadedRegion<R, S> getRegionAtSynchronised(final int chunkX, final int chunkZ) {
+        final int sectionX = chunkX >> this.sectionChunkShift;
+        final int sectionZ = chunkZ >> this.sectionChunkShift;
+        final long sectionKey = CoordinateUtils.getChunkKey(sectionX, sectionZ);
+
+        // try an optimistic read
+        {
+            final long readAttempt = this.regionLock.tryOptimisticRead();
+            final ThreadedRegionSection<R, S> optimisticSection = this.sections.get(sectionKey);
+            final ThreadedRegion<R, S> optimisticRet =
+                optimisticSection == null ? null : optimisticSection.getRegionPlain();
+            if (this.regionLock.validate(readAttempt)) {
+                return optimisticRet;
+            }
+        }
+
+        // failed, fall back to acquiring the lock
+        this.regionLock.readLock();
+        try {
+            final ThreadedRegionSection<R, S> section = this.sections.get(sectionKey);
+
+            return section == null ? null : section.getRegionPlain();
+        } finally {
+            this.regionLock.tryUnlockRead();
+        }
+    }
+
+    /**
+     * Adds a chunk to the regioniser. Note that it is illegal to add a chunk unless
+     * addChunk has not been called for it or removeChunk has been previously called.
+     *
+     * <p>
+     * Note that it is illegal to additionally call addChunk or removeChunk for the same
+     * region section in parallel.
+     * </p>
+     */
+    public void addChunk(final int chunkX, final int chunkZ) {
+        final int sectionX = chunkX >> this.sectionChunkShift;
+        final int sectionZ = chunkZ >> this.sectionChunkShift;
+        final long sectionKey = CoordinateUtils.getChunkKey(sectionX, sectionZ);
+
+        // Given that for each section, no addChunk/removeChunk can occur in parallel,
+        // we can avoid the lock IF the section exists AND it has a non-zero chunk count.
+        {
+            final ThreadedRegionSection<R, S> existing = this.sections.get(sectionKey);
+            if (existing != null && !existing.isEmpty()) {
+                existing.addChunk(chunkX, chunkZ);
+                return;
+            } // else: just acquire the write lock
+        }
+
+        this.acquireWriteLock();
+        try {
+            ThreadedRegionSection<R, S> section = this.sections.get(sectionKey);
+
+            List<ThreadedRegionSection<R, S>> newSections = new ArrayList<>();
+
+            if (section == null) {
+                // no section at all
+                section = new ThreadedRegionSection<>(sectionX, sectionZ, this, chunkX, chunkZ);
+                this.sections.put(sectionKey, section);
+                newSections.add(section);
+            } else {
+                section.addChunk(chunkX, chunkZ);
+            }
+            // due to the fast check from above, we know the section is empty whether we needed to create it or not
+
+            // enforce the adjacency invariant by creating / updating neighbour sections
+            final int createRadius = this.emptySectionCreateRadius;
+            final int searchRadius = createRadius + this.regionSectionMergeRadius;
+            ReferenceOpenHashSet<ThreadedRegion<R, S>> nearbyRegions = null;
+            for (int dx = -searchRadius; dx <= searchRadius; ++dx) {
+                for (int dz = -searchRadius; dz <= searchRadius; ++dz) {
+                    if ((dx | dz) == 0) {
+                        continue;
+                    }
+                    final int squareDistance = Math.max(Math.abs(dx), Math.abs(dz));
+                    final boolean inCreateRange = squareDistance <= createRadius;
+
+                    final int neighbourX = dx + sectionX;
+                    final int neighbourZ = dz + sectionZ;
+                    final long neighbourKey = CoordinateUtils.getChunkKey(neighbourX, neighbourZ);
+
+                    ThreadedRegionSection<R, S> neighbourSection = this.sections.get(neighbourKey);
+
+                    if (neighbourSection != null) {
+                        if (nearbyRegions == null) {
+                            nearbyRegions = new ReferenceOpenHashSet<>(((searchRadius * 2 + 1) * (searchRadius * 2 + 1)) >> 1);
+                        }
+                        nearbyRegions.add(neighbourSection.getRegionPlain());
+                    }
+
+                    if (!inCreateRange) {
+                        continue;
+                    }
+
+                    // we need to ensure the section exists
+                    if (neighbourSection != null) {
+                        // nothing else to do
+                        neighbourSection.incrementNonEmptyNeighbours();
+                        continue;
+                    }
+                    neighbourSection = new ThreadedRegionSection<>(neighbourX, neighbourZ, this, 1);
+                    if (null != this.sections.put(neighbourKey, neighbourSection)) {
+                        throw new IllegalStateException("Failed to insert new section");
+                    }
+                    newSections.add(neighbourSection);
+                }
+            }
+
+            if (newSections.isEmpty()) {
+                // if we didn't add any sections, then we don't need to merge any regions or create a region
+                return;
+            }
+
+            final ThreadedRegion<R, S> regionOfInterest;
+            final boolean regionOfInterestAlive;
+            if (nearbyRegions == null) {
+                // we can simply create a new region, don't have neighbours to worry about merging into
+                regionOfInterest = new ThreadedRegion<>(this);
+                regionOfInterestAlive = true;
+
+                for (int i = 0, len = newSections.size(); i < len; ++i) {
+                    regionOfInterest.addSection(newSections.get(i));
+                }
+
+                // only call create callback after adding sections
+                regionOfInterest.onCreate();
+            } else {
+                // need to merge the regions
+                ThreadedRegion<R, S> firstUnlockedRegion = null;
+
+                for (final ThreadedRegion<R, S> region : nearbyRegions) {
+                    if (region.isTicking()) {
+                        continue;
+                    }
+                    firstUnlockedRegion = region;
+                    if (firstUnlockedRegion.state == ThreadedRegion.STATE_READY && (!firstUnlockedRegion.mergeIntoLater.isEmpty() || !firstUnlockedRegion.expectingMergeFrom.isEmpty())) {
+                        throw new IllegalStateException("Illegal state for unlocked region " + firstUnlockedRegion);
+                    }
+                    break;
+                }
+
+                if (firstUnlockedRegion != null) {
+                    regionOfInterest = firstUnlockedRegion;
+                } else {
+                    regionOfInterest = new ThreadedRegion<>(this);
+                }
+
+                for (int i = 0, len = newSections.size(); i < len; ++i) {
+                    regionOfInterest.addSection(newSections.get(i));
+                }
+
+                // only call create callback after adding sections
+                if (firstUnlockedRegion == null) {
+                    regionOfInterest.onCreate();
+                }
+
+                if (firstUnlockedRegion != null && nearbyRegions.size() == 1) {
+                    // nothing to do further, no need to merge anything
+                    return;
+                }
+
+                // we need to now tell all the other regions to merge into the region we just created,
+                // and to merge all the ones we can immediately
+
+                for (final ThreadedRegion<R, S> region : nearbyRegions) {
+                    if (region == regionOfInterest) {
+                        continue;
+                    }
+
+                    if (!region.killAndMergeInto(regionOfInterest)) {
+                        // note: the region may already be a merge target
+                        regionOfInterest.mergeIntoLater(region);
+                    }
+                }
+
+                if (firstUnlockedRegion != null && firstUnlockedRegion.state == ThreadedRegion.STATE_READY) {
+                    // we need to retire this region if the merges added other pending merges
+                    if (!firstUnlockedRegion.mergeIntoLater.isEmpty() || !firstUnlockedRegion.expectingMergeFrom.isEmpty()) {
+                        firstUnlockedRegion.state = ThreadedRegion.STATE_TRANSIENT;
+                        this.callbacks.onRegionInactive(firstUnlockedRegion);
+                    }
+                }
+
+                // need to set alive if we created it and there are no pending merges
+                regionOfInterestAlive = firstUnlockedRegion == null && regionOfInterest.mergeIntoLater.isEmpty() && regionOfInterest.expectingMergeFrom.isEmpty();
+            }
+
+            if (regionOfInterestAlive) {
+                regionOfInterest.state = ThreadedRegion.STATE_READY;
+                if (!regionOfInterest.mergeIntoLater.isEmpty() || !regionOfInterest.expectingMergeFrom.isEmpty()) {
+                    throw new IllegalStateException("Should not happen on region " + this);
+                }
+                this.callbacks.onRegionActive(regionOfInterest);
+            }
+
+            if (regionOfInterest.state == ThreadedRegion.STATE_READY) {
+                if (!regionOfInterest.mergeIntoLater.isEmpty() || !regionOfInterest.expectingMergeFrom.isEmpty()) {
+                    throw new IllegalStateException("Should not happen on region " + this);
+                }
+            }
+        } catch (final Throwable throwable) {
+            LOGGER.error("Failed to add chunk (" + chunkX + "," + chunkZ + ")", throwable);
+            SneakyThrow.sneaky(throwable);
+            return; // unreachable
+        } finally {
+            this.releaseWriteLock();
+        }
+    }
+
+    public void removeChunk(final int chunkX, final int chunkZ) {
+        final int sectionX = chunkX >> this.sectionChunkShift;
+        final int sectionZ = chunkZ >> this.sectionChunkShift;
+        final long sectionKey = CoordinateUtils.getChunkKey(sectionX, sectionZ);
+
+        // Given that for each section, no addChunk/removeChunk can occur in parallel,
+        // we can avoid the lock IF the section exists AND it has a chunk count > 1
+        final ThreadedRegionSection<R, S> section = this.sections.get(sectionKey);
+        if (section == null) {
+            throw new IllegalStateException("Chunk (" + chunkX + "," + chunkZ + ") has no section");
+        }
+        if (!section.hasOnlyOneChunk()) {
+            // chunk will not go empty, so we don't need to acquire the lock
+            section.removeChunk(chunkX, chunkZ);
+            return;
+        }
+
+        this.acquireWriteLock();
+        try {
+            section.removeChunk(chunkX, chunkZ);
+
+            final int searchRadius = this.emptySectionCreateRadius;
+            for (int dx = -searchRadius; dx <= searchRadius; ++dx) {
+                for (int dz = -searchRadius; dz <= searchRadius; ++dz) {
+                    if ((dx | dz) == 0) {
+                        continue;
+                    }
+
+                    final int neighbourX = dx + sectionX;
+                    final int neighbourZ = dz + sectionZ;
+                    final long neighbourKey = CoordinateUtils.getChunkKey(neighbourX, neighbourZ);
+
+                    final ThreadedRegionSection<R, S> neighbourSection = this.sections.get(neighbourKey);
+
+                    // should be non-null here always
+                    neighbourSection.decrementNonEmptyNeighbours();
+                }
+            }
+        } catch (final Throwable throwable) {
+            LOGGER.error("Failed to add chunk (" + chunkX + "," + chunkZ + ")", throwable);
+            SneakyThrow.sneaky(throwable);
+            return; // unreachable
+        } finally {
+            this.releaseWriteLock();
+        }
+    }
+
+    // must hold regionLock
+    private void onRegionRelease(final ThreadedRegion<R, S> region) {
+        if (!region.mergeIntoLater.isEmpty()) {
+            throw new IllegalStateException("Region " + region + " should not have any regions to merge into!");
+        }
+
+        final boolean hasExpectingMerges = !region.expectingMergeFrom.isEmpty();
+
+        // is this region supposed to merge into any other region?
+        if (hasExpectingMerges) {
+            // merge the regions into this one
+            final ReferenceOpenHashSet<ThreadedRegion<R, S>> expectingMergeFrom = region.expectingMergeFrom.clone();
+            for (final ThreadedRegion<R, S> mergeFrom : expectingMergeFrom) {
+                if (!mergeFrom.killAndMergeInto(region)) {
+                    throw new IllegalStateException("Merge from region " + mergeFrom + " should be killable! Trying to merge into " + region);
+                }
+            }
+
+            if (!region.expectingMergeFrom.isEmpty()) {
+                throw new IllegalStateException("Region " + region + " should no longer have merge requests after mering from " + expectingMergeFrom);
+            }
+
+            if (!region.mergeIntoLater.isEmpty()) {
+                // There is another nearby ticking region that we need to merge into
+                region.state = ThreadedRegion.STATE_TRANSIENT;
+                this.callbacks.onRegionInactive(region);
+                // return to avoid removing dead sections or splitting, these actions will be performed
+                // by the region we merge into
+                return;
+            }
+        }
+
+        // now check whether we need to recalculate regions
+        final boolean removeDeadSections = hasExpectingMerges || region.hasNoAliveSections()
+            || (region.sectionByKey.size() >= this.minSectionRecalcCount && region.getDeadSectionPercent() >= this.maxDeadRegionPercent);
+        final boolean removedDeadSections = removeDeadSections && !region.deadSections.isEmpty();
+        if (removeDeadSections) {
+            // kill dead sections
+            for (final ThreadedRegionSection<R, S> deadSection : region.deadSections) {
+                final long key = CoordinateUtils.getChunkKey(deadSection.sectionX, deadSection.sectionZ);
+
+                if (!deadSection.isEmpty()) {
+                    throw new IllegalStateException("Dead section '" + deadSection.toStringWithRegion() + "' is marked dead but has chunks!");
+                }
+                if (deadSection.hasNonEmptyNeighbours()) {
+                    throw new IllegalStateException("Dead section '" + deadSection.toStringWithRegion() + "' is marked dead but has non-empty neighbours!");
+                }
+                if (!region.sectionByKey.remove(key, deadSection)) {
+                    throw new IllegalStateException("Region " + region + " has inconsistent state, it should contain section " + deadSection);
+                }
+                if (this.sections.remove(key) != deadSection) {
+                    throw new IllegalStateException("Cannot remove dead section '" +
+                        deadSection.toStringWithRegion() + "' from section state! State at section coordinate: " + this.sections.get(key));
+                }
+            }
+            region.deadSections.clear();
+        }
+
+        // if we removed dead sections, we should check if the region can be split into smaller ones
+        // otherwise, the region remains alive
+        if (!removedDeadSections) {
+            // didn't remove dead sections, don't check for split
+            region.state = ThreadedRegion.STATE_READY;
+            if (!region.expectingMergeFrom.isEmpty() || !region.mergeIntoLater.isEmpty()) {
+                throw new IllegalStateException("Illegal state " + region);
+            }
+            return;
+        }
+
+        // first, we need to build copy of coordinate->section map of all sections in recalculate
+        final Long2ReferenceOpenHashMap<ThreadedRegionSection<R, S>> recalculateSections = region.sectionByKey.clone();
+
+        if (recalculateSections.isEmpty()) {
+            // looks like the region's sections were all dead, and now there is no region at all
+            region.state = ThreadedRegion.STATE_DEAD;
+            region.onRemove(true);
+            return;
+        }
+
+        // merge radius is max, since recalculateSections includes the dead or empty sections
+        final int mergeRadius = Math.max(this.regionSectionMergeRadius, this.emptySectionCreateRadius);
+
+        final List<List<ThreadedRegionSection<R, S>>> newRegions = new ArrayList<>();
+        while (!recalculateSections.isEmpty()) {
+            // select any section, then BFS around it to find all of its neighbours to form a region
+            // once no more neighbours are found, the region is complete
+            final List<ThreadedRegionSection<R, S>> currRegion = new ArrayList<>();
+            final Iterator<ThreadedRegionSection<R, S>> firstIterator = recalculateSections.values().iterator();
+
+            currRegion.add(firstIterator.next());
+            firstIterator.remove();
+            search_loop:
+            for (int idx = 0; idx < currRegion.size(); ++idx) {
+                final ThreadedRegionSection<R, S> curr = currRegion.get(idx);
+                final int centerX = curr.sectionX;
+                final int centerZ = curr.sectionZ;
+
+                // find neighbours in radius
+                for (int dz = -mergeRadius; dz <= mergeRadius; ++dz) {
+                    for (int dx = -mergeRadius; dx <= mergeRadius; ++dx) {
+                        if ((dx | dz) == 0) {
+                            continue;
+                        }
+
+                        final ThreadedRegionSection<R, S> section = recalculateSections.remove(CoordinateUtils.getChunkKey(dx + centerX, dz + centerZ));
+                        if (section == null) {
+                            continue;
+                        }
+
+                        currRegion.add(section);
+
+                        if (recalculateSections.isEmpty()) {
+                            // no point in searching further
+                            break search_loop;
+                        }
+                    }
+                }
+            }
+
+            newRegions.add(currRegion);
+        }
+
+        // now we have split the regions into separate parts, we can split recalculate
+
+        if (newRegions.size() == 1) {
+            // no need to split anything, we're done here
+            region.state = ThreadedRegion.STATE_READY;
+            if (!region.expectingMergeFrom.isEmpty() || !region.mergeIntoLater.isEmpty()) {
+                throw new IllegalStateException("Illegal state " + region);
+            }
+            return;
+        }
+
+        final List<ThreadedRegion<R, S>> newRegionObjects = new ArrayList<>(newRegions.size());
+        for (int i = 0, len = newRegions.size(); i < len; ++i) {
+            newRegionObjects.add(new ThreadedRegion<>(this));
+        }
+
+        this.callbacks.preSplit(region, newRegionObjects);
+
+        // need to split the region, so we need to kill the old one first
+        region.state = ThreadedRegion.STATE_DEAD;
+        region.onRemove(true);
+
+        // create new regions
+        final Long2ReferenceOpenHashMap<ThreadedRegion<R, S>> newRegionsMap = new Long2ReferenceOpenHashMap<>();
+        final ReferenceOpenHashSet<ThreadedRegion<R, S>> newRegionsSet = new ReferenceOpenHashSet<>(newRegionObjects);
+
+        for (int i = 0, len = newRegions.size(); i < len; i++) {
+            final List<ThreadedRegionSection<R, S>> sections = newRegions.get(i);
+            final ThreadedRegion<R, S> newRegion = newRegionObjects.get(i);
+
+            for (final ThreadedRegionSection<R, S> section : sections) {
+                section.setRegionRelease(null);
+                newRegion.addSection(section);
+                final ThreadedRegion<R, S> curr = newRegionsMap.putIfAbsent(section.sectionKey, newRegion);
+                if (curr != null) {
+                    throw new IllegalStateException("Expected no region at " + section + ", but got " + curr + ", should have put " + newRegion);
+                }
+            }
+        }
+
+        region.split(newRegionsMap, newRegionsSet);
+
+        // only after invoking data callbacks
+
+        for (final ThreadedRegion<R, S> newRegion : newRegionsSet) {
+            newRegion.state = ThreadedRegion.STATE_READY;
+            if (!newRegion.expectingMergeFrom.isEmpty() || !newRegion.mergeIntoLater.isEmpty()) {
+                throw new IllegalStateException("Illegal state " + newRegion);
+            }
+            newRegion.onCreate();
+            this.callbacks.onRegionActive(newRegion);
+        }
+    }
+
+    public static final class ThreadedRegion<R extends ThreadedRegionData<R, S>, S extends ThreadedRegionSectionData> {
+
+        private static final AtomicLong REGION_ID_GENERATOR = new AtomicLong();
+
+        private static final int STATE_TRANSIENT     = 0;
+        private static final int STATE_READY         = 1;
+        private static final int STATE_TICKING       = 2;
+        private static final int STATE_DEAD          = 3;
+
+        public final long id;
+
+        private int state;
+
+        private final Long2ReferenceOpenHashMap<ThreadedRegionSection<R, S>> sectionByKey = new Long2ReferenceOpenHashMap<>();
+        private final ReferenceOpenHashSet<ThreadedRegionSection<R, S>> deadSections = new ReferenceOpenHashSet<>();
+
+        public final ThreadedRegionizer<R, S> regioniser;
+
+        private final R data;
+
+        private final ReferenceOpenHashSet<ThreadedRegion<R, S>> mergeIntoLater = new ReferenceOpenHashSet<>();
+        private final ReferenceOpenHashSet<ThreadedRegion<R, S>> expectingMergeFrom = new ReferenceOpenHashSet<>();
+
+        public ThreadedRegion(final ThreadedRegionizer<R, S> regioniser) {
+            this.regioniser = regioniser;
+            this.id = REGION_ID_GENERATOR.getAndIncrement();
+            this.state = STATE_TRANSIENT;
+            this.data = regioniser.callbacks.createNewData(this);
+        }
+
+        public LongArrayList getOwnedSections() {
+            final boolean lock = this.regioniser.writeLockOwner != Thread.currentThread();
+            if (lock) {
+                this.regioniser.regionLock.readLock();
+            }
+            try {
+                final LongArrayList ret = new LongArrayList(this.sectionByKey.size());
+                ret.addAll(this.sectionByKey.keySet());
+
+                return ret;
+            } finally {
+                if (lock) {
+                    this.regioniser.regionLock.tryUnlockRead();
+                }
+            }
+        }
+
+        /**
+         * returns an iterator directly over the sections map. This is only to be used by a thread which is _ticking_
+         * 'this' region.
+         */
+        public LongIterator getOwnedSectionsUnsynchronised() {
+            return this.sectionByKey.keySet().iterator();
+        }
+
+        public LongArrayList getOwnedChunks() {
+            final boolean lock = this.regioniser.writeLockOwner != Thread.currentThread();
+            if (lock) {
+                this.regioniser.regionLock.readLock();
+            }
+            try {
+                final LongArrayList ret = new LongArrayList();
+                for (final ThreadedRegionSection<R, S> section : this.sectionByKey.values()) {
+                    ret.addAll(section.getChunks());
+                }
+
+                return ret;
+            } finally {
+                if (lock) {
+                    this.regioniser.regionLock.tryUnlockRead();
+                }
+            }
+        }
+
+        public Long getCenterSection() {
+            final LongArrayList sections = this.getOwnedSections();
+
+            final LongComparator comparator = (final long k1, final long k2) -> {
+                final int x1 = CoordinateUtils.getChunkX(k1);
+                final int x2 = CoordinateUtils.getChunkX(k2);
+
+                final int z1 = CoordinateUtils.getChunkZ(x1);
+                final int z2 = CoordinateUtils.getChunkZ(x2);
+
+                final int zCompare = Integer.compare(z1, z2);
+                if (zCompare != 0) {
+                    return zCompare;
+                }
+
+                return Integer.compare(x1, x2);
+            };
+
+            // note: regions don't always have a chunk section at this point, because the region may have been killed
+            if (sections.isEmpty()) {
+                return null;
+            }
+
+            sections.sort(comparator);
+
+            return Long.valueOf(sections.getLong(sections.size() >> 1));
+        }
+
+        public ChunkPos getCenterChunk() {
+            final LongArrayList chunks = this.getOwnedChunks();
+
+            final LongComparator comparator = (final long k1, final long k2) -> {
+                final int x1 = CoordinateUtils.getChunkX(k1);
+                final int x2 = CoordinateUtils.getChunkX(k2);
+
+                final int z1 = CoordinateUtils.getChunkZ(k1);
+                final int z2 = CoordinateUtils.getChunkZ(k2);
+
+                final int zCompare = Integer.compare(z1, z2);
+                if (zCompare != 0) {
+                    return zCompare;
+                }
+
+                return Integer.compare(x1, x2);
+            };
+            chunks.sort(comparator);
+
+            // note: regions don't always have a chunk at this point, because the region may have been killed
+            if (chunks.isEmpty()) {
+                return null;
+            }
+
+            final long middle = chunks.getLong(chunks.size() >> 1);
+
+            return new ChunkPos(CoordinateUtils.getChunkX(middle), CoordinateUtils.getChunkZ(middle));
+        }
+
+        private void onCreate() {
+            this.regioniser.onRegionCreate(this);
+            this.regioniser.callbacks.onRegionCreate(this);
+        }
+
+        private void onRemove(final boolean wasActive) {
+            if (wasActive) {
+                this.regioniser.callbacks.onRegionInactive(this);
+            }
+            this.regioniser.callbacks.onRegionDestroy(this);
+            this.regioniser.onRegionDestroy(this);
+        }
+
+        private final boolean hasNoAliveSections() {
+            return this.deadSections.size() == this.sectionByKey.size();
+        }
+
+        private final double getDeadSectionPercent() {
+            return (double)this.deadSections.size() / (double)this.sectionByKey.size();
+        }
+
+        private void split(final Long2ReferenceOpenHashMap<ThreadedRegion<R, S>> into, final ReferenceOpenHashSet<ThreadedRegion<R, S>> regions) {
+            if (this.data != null) {
+                this.data.split(this.regioniser, into, regions);
+            }
+        }
+
+        boolean killAndMergeInto(final ThreadedRegion<R, S> mergeTarget) {
+            if (this.state == STATE_TICKING) {
+                return false;
+            }
+
+            this.regioniser.callbacks.preMerge(this, mergeTarget);
+
+            this.tryKill();
+
+            this.mergeInto(mergeTarget);
+
+            return true;
+        }
+
+        private void mergeInto(final ThreadedRegion<R, S> mergeTarget) {
+            if (this == mergeTarget) {
+                throw new IllegalStateException("Cannot merge a region onto itself");
+            }
+            if (!this.isDead()) {
+                throw new IllegalStateException("Source region is not dead! Source " + this + ", target " + mergeTarget);
+            } else if (mergeTarget.isDead()) {
+                throw new IllegalStateException("Target region is dead! Source " + this + ", target " + mergeTarget);
+            }
+
+            for (final ThreadedRegionSection<R, S> section : this.sectionByKey.values()) {
+                section.setRegionRelease(null);
+                mergeTarget.addSection(section);
+            }
+            for (final ThreadedRegionSection<R, S> deadSection : this.deadSections) {
+                if (this.sectionByKey.get(deadSection.sectionKey) != deadSection) {
+                    throw new IllegalStateException("Source region does not even contain its own dead sections! Missing " + deadSection + " from region " + this);
+                }
+                if (!mergeTarget.deadSections.add(deadSection)) {
+                    throw new IllegalStateException("Merge target contains dead section from source! Has " + deadSection + " from region " + this);
+                }
+            }
+
+            // forward merge expectations
+            for (final ThreadedRegion<R, S> region : this.expectingMergeFrom) {
+                if (!region.mergeIntoLater.remove(this)) {
+                    throw new IllegalStateException("Region " + region + " was not supposed to merge into " + this + "?");
+                }
+                if (region != mergeTarget) {
+                    region.mergeIntoLater(mergeTarget);
+                }
+            }
+
+            // forward merge into
+            for (final ThreadedRegion<R, S> region : this.mergeIntoLater) {
+                if (!region.expectingMergeFrom.remove(this)) {
+                    throw new IllegalStateException("Region " + this + " was not supposed to merge into " + region + "?");
+                }
+                if (region != mergeTarget) {
+                    mergeTarget.mergeIntoLater(region);
+                }
+            }
+
+            // finally, merge data
+            if (this.data != null) {
+                this.data.mergeInto(mergeTarget);
+            }
+        }
+
+        private void mergeIntoLater(final ThreadedRegion<R, S> region) {
+            if (region.isDead()) {
+                throw new IllegalStateException("Trying to merge later into a dead region: " + region);
+            }
+            final boolean add1, add2;
+            if ((add1 = this.mergeIntoLater.add(region)) != (add2 = region.expectingMergeFrom.add(this))) {
+                throw new IllegalStateException("Inconsistent state between target merge " + region + " and this " + this + ": add1,add2:" + add1 + "," + add2);
+            }
+        }
+
+        private boolean tryKill() {
+            switch (this.state) {
+                case STATE_TRANSIENT: {
+                    this.state = STATE_DEAD;
+                    this.onRemove(false);
+                    return true;
+                }
+                case STATE_READY: {
+                    this.state = STATE_DEAD;
+                    this.onRemove(true);
+                    return true;
+                }
+                case STATE_TICKING: {
+                    return false;
+                }
+                case STATE_DEAD: {
+                    throw new IllegalStateException("Already dead");
+                }
+                default: {
+                    throw new IllegalStateException("Unknown state: " + this.state);
+                }
+            }
+        }
+
+        private boolean isDead() {
+            return this.state == STATE_DEAD;
+        }
+
+        private boolean isTicking() {
+            return this.state == STATE_TICKING;
+        }
+
+        private void removeDeadSection(final ThreadedRegionSection<R, S> section) {
+            this.deadSections.remove(section);
+        }
+
+        private void addDeadSection(final ThreadedRegionSection<R, S> section) {
+            this.deadSections.add(section);
+        }
+
+        private void addSection(final ThreadedRegionSection<R, S> section) {
+            if (section.getRegionPlain() != null) {
+                throw new IllegalStateException("Section already has region");
+            }
+            if (this.sectionByKey.putIfAbsent(section.sectionKey, section) != null) {
+                throw new IllegalStateException("Already have section " + section + ", mapped to " + this.sectionByKey.get(section.sectionKey));
+            }
+            section.setRegionRelease(this);
+        }
+
+        public R getData() {
+            return this.data;
+        }
+
+        public boolean tryMarkTicking(final BooleanSupplier abort) {
+            this.regioniser.acquireWriteLock();
+            try {
+                if (this.state != STATE_READY || abort.getAsBoolean()) {
+                    return false;
+                }
+
+                if (!this.mergeIntoLater.isEmpty() || !this.expectingMergeFrom.isEmpty()) {
+                    throw new IllegalStateException("Region " + this + " should not be ready");
+                }
+
+                this.state = STATE_TICKING;
+                return true;
+            } finally {
+                this.regioniser.releaseWriteLock();
+            }
+        }
+
+        public boolean markNotTicking() {
+            this.regioniser.acquireWriteLock();
+            try {
+                if (this.state != STATE_TICKING) {
+                    throw new IllegalStateException("Attempting to release non-locked state");
+                }
+
+                this.regioniser.onRegionRelease(this);
+
+                return this.state == STATE_READY;
+            } catch (final Throwable throwable) {
+                LOGGER.error("Failed to acquire region " + this, throwable);
+                SneakyThrow.sneaky(throwable);
+                return false; // unreachable
+            } finally {
+                this.regioniser.releaseWriteLock();
+            }
+        }
+
+        @Override
+        public String toString() {
+            final StringBuilder ret = new StringBuilder(128);
+
+            ret.append("ThreadedRegion{");
+            ret.append("state=").append(this.state).append(',');
+            // To avoid recursion in toString, maybe fix later?
+            //ret.append("mergeIntoLater=").append(this.mergeIntoLater).append(',');
+            //ret.append("expectingMergeFrom=").append(this.expectingMergeFrom).append(',');
+
+            ret.append("sectionCount=").append(this.sectionByKey.size()).append(',');
+            ret.append("sections=[");
+            for (final Iterator<ThreadedRegionSection<R, S>> iterator = this.sectionByKey.values().iterator(); iterator.hasNext();) {
+                final ThreadedRegionSection<R, S> section = iterator.next();
+
+                ret.append(section.toString());
+                if (iterator.hasNext()) {
+                    ret.append(',');
+                }
+            }
+            ret.append(']');
+
+            ret.append('}');
+            return ret.toString();
+        }
+    }
+
+    public static final class ThreadedRegionSection<R extends ThreadedRegionData<R, S>, S extends ThreadedRegionSectionData> {
+
+        public final int sectionX;
+        public final int sectionZ;
+        public final long sectionKey;
+        private final long[] chunksBitset;
+        private int chunkCount;
+        private int nonEmptyNeighbours;
+
+        private ThreadedRegion<R, S> region;
+        private static final VarHandle REGION_HANDLE = ConcurrentUtil.getVarHandle(ThreadedRegionSection.class, "region", ThreadedRegion.class);
+
+        public final ThreadedRegionizer<R, S> regioniser;
+
+        private final int regionChunkShift;
+        private final int regionChunkMask;
+
+        private final S data;
+
+        private ThreadedRegion<R, S> getRegionPlain() {
+            return (ThreadedRegion<R, S>)REGION_HANDLE.get(this);
+        }
+
+        private ThreadedRegion<R, S> getRegionAcquire() {
+            return (ThreadedRegion<R, S>)REGION_HANDLE.getAcquire(this);
+        }
+
+        private void setRegionRelease(final ThreadedRegion<R, S> value) {
+            REGION_HANDLE.setRelease(this, value);
+        }
+
+        // creates an empty section with zero non-empty neighbours
+        private ThreadedRegionSection(final int sectionX, final int sectionZ, final ThreadedRegionizer<R, S> regioniser) {
+            this.sectionX = sectionX;
+            this.sectionZ = sectionZ;
+            this.sectionKey = CoordinateUtils.getChunkKey(sectionX, sectionZ);
+            this.chunksBitset = new long[Math.max(1, regioniser.regionSectionChunkSize * regioniser.regionSectionChunkSize / Long.SIZE)];
+            this.regioniser = regioniser;
+            this.regionChunkShift = regioniser.sectionChunkShift;
+            this.regionChunkMask = regioniser.regionSectionChunkSize - 1;
+            this.data = regioniser.callbacks
+                .createNewSectionData(sectionX, sectionZ, this.regionChunkShift);
+        }
+
+        // creates a section with an initial chunk with zero non-empty neighbours
+        private ThreadedRegionSection(final int sectionX, final int sectionZ, final ThreadedRegionizer<R, S> regioniser,
+                                      final int chunkXInit, final int chunkZInit) {
+            this(sectionX, sectionZ, regioniser);
+
+            final int initIndex = this.getChunkIndex(chunkXInit, chunkZInit);
+            this.chunkCount = 1;
+            this.chunksBitset[initIndex >>> 6] = 1L << (initIndex & (Long.SIZE - 1)); // index / Long.SIZE
+        }
+
+        // creates an empty section with the specified number of non-empty neighbours
+        private ThreadedRegionSection(final int sectionX, final int sectionZ, final ThreadedRegionizer<R, S> regioniser,
+                                      final int nonEmptyNeighbours) {
+            this(sectionX, sectionZ, regioniser);
+
+            this.nonEmptyNeighbours = nonEmptyNeighbours;
+        }
+
+        public LongArrayList getChunks() {
+            final LongArrayList ret = new LongArrayList();
+
+            if (this.chunkCount == 0) {
+                return ret;
+            }
+
+            final int shift = this.regionChunkShift;
+            final int mask = this.regionChunkMask;
+            final int offsetX = this.sectionX << shift;
+            final int offsetZ = this.sectionZ << shift;
+
+            final long[] bitset = this.chunksBitset;
+            for (int arrIdx = 0, arrLen = bitset.length; arrIdx < arrLen; ++arrIdx) {
+                long value = bitset[arrIdx];
+
+                for (int i = 0, bits = Long.bitCount(value); i < bits; ++i) {
+                    final int valueIdx = Long.numberOfTrailingZeros(value);
+                    value ^= io.papermc.paper.util.IntegerUtil.getTrailingBit(value);
+
+                    final int idx = valueIdx | (arrIdx << 6);
+
+                    final int localX = idx & mask;
+                    final int localZ = (idx >>> shift) & mask;
+
+                    ret.add(CoordinateUtils.getChunkKey(localX | offsetX, localZ | offsetZ));
+                }
+            }
+
+            return ret;
+        }
+
+        private boolean isEmpty() {
+            return this.chunkCount == 0;
+        }
+
+        private boolean hasOnlyOneChunk() {
+            return this.chunkCount == 1;
+        }
+
+        public boolean hasNonEmptyNeighbours() {
+            return this.nonEmptyNeighbours != 0;
+        }
+
+        /**
+         * Returns the section data associated with this region section. May be {@code null}.
+         */
+        public S getData() {
+            return this.data;
+        }
+
+        /**
+         * Returns the region that owns this section. Unsynchronised access may produce outdateed or transient results.
+         */
+        public ThreadedRegion<R, S> getRegion() {
+            return this.getRegionAcquire();
+        }
+
+        private int getChunkIndex(final int chunkX, final int chunkZ) {
+            return (chunkX & this.regionChunkMask) | ((chunkZ & this.regionChunkMask) << this.regionChunkShift);
+        }
+
+        private void markAlive() {
+            this.getRegionPlain().removeDeadSection(this);
+        }
+
+        private void markDead() {
+            this.getRegionPlain().addDeadSection(this);
+        }
+
+        private void incrementNonEmptyNeighbours() {
+            if (++this.nonEmptyNeighbours == 1 && this.chunkCount == 0) {
+                this.markAlive();
+            }
+            final int createRadius = this.regioniser.emptySectionCreateRadius;
+            if (this.nonEmptyNeighbours >= ((createRadius * 2 + 1) * (createRadius * 2 + 1))) {
+                throw new IllegalStateException("Non empty neighbours exceeded max value for radius " + createRadius);
+            }
+        }
+
+        private void decrementNonEmptyNeighbours() {
+            if (--this.nonEmptyNeighbours == 0 && this.chunkCount == 0) {
+                this.markDead();
+            }
+            if (this.nonEmptyNeighbours < 0) {
+                throw new IllegalStateException("Non empty neighbours reached zero");
+            }
+        }
+
+        /**
+         * Returns whether the chunk was zero. Effectively returns whether the caller needs to create
+         * dead sections / increase non-empty neighbour count for neighbouring sections.
+         */
+        private boolean addChunk(final int chunkX, final int chunkZ) {
+            final int index = this.getChunkIndex(chunkX, chunkZ);
+            final long bitset = this.chunksBitset[index >>> 6]; // index / Long.SIZE
+            final long after = this.chunksBitset[index >>> 6] = bitset | (1L << (index & (Long.SIZE - 1)));
+            if (after == bitset) {
+                throw new IllegalStateException("Cannot add a chunk to a section which already has the chunk! RegionSection: " + this + ", global chunk: " + new ChunkPos(chunkX, chunkZ).toString());
+            }
+            final boolean notEmpty = ++this.chunkCount == 1;
+            if (notEmpty && this.nonEmptyNeighbours == 0) {
+                this.markAlive();
+            }
+            return notEmpty;
+        }
+
+        /**
+         * Returns whether the chunk count is now zero. Effectively returns whether
+         * the caller needs to decrement the neighbour count for neighbouring sections.
+         */
+        private boolean removeChunk(final int chunkX, final int chunkZ) {
+            final int index = this.getChunkIndex(chunkX, chunkZ);
+            final long before = this.chunksBitset[index >>> 6]; // index / Long.SIZE
+            final long bitset = this.chunksBitset[index >>> 6] = before & ~(1L << (index & (Long.SIZE - 1)));
+            if (before == bitset) {
+                throw new IllegalStateException("Cannot remove a chunk from a section which does not have that chunk! RegionSection: " + this + ", global chunk: " + new ChunkPos(chunkX, chunkZ).toString());
+            }
+            final boolean empty = --this.chunkCount == 0;
+            if (empty && this.nonEmptyNeighbours == 0) {
+                this.markDead();
+            }
+            return empty;
+        }
+
+        @Override
+        public String toString() {
+            return "RegionSection{" +
+                "sectionCoordinate=" + new ChunkPos(this.sectionX, this.sectionZ).toString() + "," +
+                "chunkCount=" + this.chunkCount + "," +
+                "chunksBitset=" + toString(this.chunksBitset) + "," +
+                "nonEmptyNeighbours=" + this.nonEmptyNeighbours + "," +
+                "hash=" + this.hashCode() +
+                "}";
+        }
+
+        public String toStringWithRegion() {
+            return "RegionSection{" +
+                "sectionCoordinate=" + new ChunkPos(this.sectionX, this.sectionZ).toString() + "," +
+                "chunkCount=" + this.chunkCount + "," +
+                "chunksBitset=" + toString(this.chunksBitset) + "," +
+                "hash=" + this.hashCode() + "," +
+                "nonEmptyNeighbours=" + this.nonEmptyNeighbours + "," +
+                "region=" + this.getRegionAcquire() +
+                "}";
+        }
+
+        private static String toString(final long[] array) {
+            final StringBuilder ret = new StringBuilder();
+            final char[] zeros = new char[Long.SIZE / 4];
+            for (final long value : array) {
+                // zero pad the hex string
+                Arrays.fill(zeros, '0');
+                final String string = Long.toHexString(value);
+                System.arraycopy(string.toCharArray(), 0, zeros, zeros.length - string.length(), string.length());
+
+                ret.append(zeros);
+            }
+
+            return ret.toString();
+        }
+    }
+
+    public static interface ThreadedRegionData<R extends ThreadedRegionData<R, S>, S extends ThreadedRegionSectionData> {
+
+        /**
+         * Splits this region data into the specified regions set.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param regioniser Regioniser for which the regions reside in.
+         * @param into A map of region section coordinate key to the region that owns the section.
+         * @param regions The set of regions to split into.
+         */
+        public void split(final ThreadedRegionizer<R, S> regioniser, final Long2ReferenceOpenHashMap<ThreadedRegion<R, S>> into,
+                          final ReferenceOpenHashSet<ThreadedRegion<R, S>> regions);
+
+        /**
+         * Callback to merge {@code this} region data into the specified region. The state of the region is undefined
+         * except that its region data is already created.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param into Specified region.
+         */
+        public void mergeInto(final ThreadedRegion<R, S> into);
+    }
+
+    public static interface ThreadedRegionSectionData {}
+
+    public static interface RegionCallbacks<R extends ThreadedRegionData<R, S>, S extends ThreadedRegionSectionData> {
+
+        /**
+         * Creates new section data for the specified section x and section z.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param sectionX x coordinate of the section.
+         * @param sectionZ z coordinate of the section.
+         * @param sectionShift The signed right shift value that can be applied to any chunk coordinate that
+         *                     produces a section coordinate.
+         * @return New section data, may be {@code null}.
+         */
+        public S createNewSectionData(final int sectionX, final int sectionZ, final int sectionShift);
+
+        /**
+         * Creates new region data for the specified region.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param forRegion The region to create the data for.
+         * @return New region data, may be {@code null}.
+         */
+        public R createNewData(final ThreadedRegion<R, S> forRegion);
+
+        /**
+         * Callback for when a region is created. This is invoked after the region is completely set up,
+         * so its data and owned sections are reliable to inspect.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param region The region that was created.
+         */
+        public void onRegionCreate(final ThreadedRegion<R, S> region);
+
+        /**
+         * Callback for when a region is destroyed. This is invoked before the region is actually destroyed; so
+         * its data and owned sections are reliable to inspect.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param region The region that is about to be destroyed.
+         */
+        public void onRegionDestroy(final ThreadedRegion<R, S> region);
+
+        /**
+         * Callback for when a region is considered "active." An active region x is a non-destroyed region which
+         * is not scheduled to merge into another region y and there are no non-destroyed regions z which are
+         * scheduled to merge into the region x. Equivalently, an active region is not directly adjacent to any
+         * other region considering the regioniser's empty section radius.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param region The region that is now active.
+         */
+        public void onRegionActive(final ThreadedRegion<R, S> region);
+
+        /**
+         * Callback for when a region transistions becomes inactive. An inactive region is non-destroyed, but
+         * has neighbouring adjacent regions considering the regioniser's empty section radius. Effectively,
+         * an inactive region may not tick and needs to be merged into its neighbouring regions.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param region The region that is now inactive.
+         */
+        public void onRegionInactive(final ThreadedRegion<R, S> region);
+
+        /**
+         * Callback for when a region (from) is about to be merged into a target region (into). Note that
+         * {@code from} is still alive and is a distinct region.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param from The region that will be merged into the target.
+         * @param into The target of the merge.
+         */
+        public void preMerge(final ThreadedRegion<R, S> from, final ThreadedRegion<R, S> into);
+
+        /**
+         * Callback for when a region (from) is about to be split into a list of target region (into). Note that
+         * {@code from} is still alive, while the list of target regions are not initialised.
+         * <p>
+         * <b>Note:</b>
+         * </p>
+         * <p>
+         * This function is always called while holding critical locks and as such should not attempt to block on anything, and
+         * should NOT retrieve or modify ANY world state.
+         * </p>
+         * @param from The region that will be merged into the target.
+         * @param into The list of regions to split into.
+         */
+        public void preSplit(final ThreadedRegion<R, S> from, final List<ThreadedRegion<R, S>> into);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/TickData.java b/src/main/java/io/papermc/paper/threadedregions/TickData.java
new file mode 100644
index 0000000000000000000000000000000000000000..29f9fed5f02530b3256e6b993e607d4647daa7b6
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/TickData.java
@@ -0,0 +1,333 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.util.TimeUtil;
+import io.papermc.paper.util.IntervalledCounter;
+import it.unimi.dsi.fastutil.longs.LongArrayList;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public final class TickData {
+
+    private final long interval; // ns
+
+    private final ArrayDeque<TickRegionScheduler.TickTime> timeData = new ArrayDeque<>();
+
+    public TickData(final long intervalNS) {
+        this.interval = intervalNS;
+    }
+
+    public void addDataFrom(final TickRegionScheduler.TickTime time) {
+        final long start = time.tickStart();
+
+        TickRegionScheduler.TickTime first;
+        while ((first = this.timeData.peekFirst()) != null) {
+            // only remove data completely out of window
+            if ((start - first.tickEnd()) <= this.interval) {
+                break;
+            }
+            this.timeData.pollFirst();
+        }
+
+        this.timeData.add(time);
+    }
+
+    // fromIndex inclusive, toIndex exclusive
+    // will throw if arr.length == 0
+    private static double median(final long[] arr, final int fromIndex, final int toIndex) {
+        final int len = toIndex - fromIndex;
+        final int middle = fromIndex + (len >>> 1);
+        if ((len & 1) == 0) {
+            // even, average the two middle points
+            return (double)(arr[middle - 1] + arr[middle]) / 2.0;
+        } else {
+            // odd, just grab the middle
+            return (double)arr[middle];
+        }
+    }
+
+    // will throw if arr.length == 0
+    private static SegmentData computeSegmentData(final long[] arr, final int fromIndex, final int toIndex,
+                                                  final boolean inverse) {
+        final int len = toIndex - fromIndex;
+        long sum = 0L;
+        final double median = median(arr, fromIndex, toIndex);
+        long min = arr[0];
+        long max = arr[0];
+
+        for (int i = fromIndex; i < toIndex; ++i) {
+            final long val = arr[i];
+            sum += val;
+            if (val < min) {
+                min = val;
+            }
+            if (val > max) {
+                max = val;
+            }
+        }
+
+        if (inverse) {
+            // for positive a,b we have that a >= b if and only if 1/a <= 1/b
+            return new SegmentData(
+                len,
+                (double)len / ((double)sum / 1.0E9),
+                1.0E9 / median,
+                1.0E9 / (double)max,
+                1.0E9 / (double)min
+            );
+        } else {
+            return new SegmentData(
+                len,
+                (double)sum / (double)len,
+                median,
+                (double)min,
+                (double)max
+            );
+        }
+    }
+
+    private static SegmentedAverage computeSegmentedAverage(final long[] data, final int allStart, final int allEnd,
+                                                            final int percent99BestStart, final int percent99BestEnd,
+                                                            final int percent95BestStart, final int percent95BestEnd,
+                                                            final int percent1WorstStart, final int percent1WorstEnd,
+                                                            final int percent5WorstStart, final int percent5WorstEnd,
+                                                            final boolean inverse) {
+        return new SegmentedAverage(
+            computeSegmentData(data, allStart, allEnd, inverse),
+            computeSegmentData(data, percent99BestStart, percent99BestEnd, inverse),
+            computeSegmentData(data, percent95BestStart, percent95BestEnd, inverse),
+            computeSegmentData(data, percent1WorstStart, percent1WorstEnd, inverse),
+            computeSegmentData(data, percent5WorstStart, percent5WorstEnd, inverse)
+        );
+    }
+
+    private static record TickInformation(
+        long differenceFromLastTick,
+        long tickTime,
+        long tickTimeCPU
+    ) {}
+
+    // rets null if there is no data
+    public TickReportData generateTickReport(final TickRegionScheduler.TickTime inProgress, final long endTime) {
+        if (this.timeData.isEmpty() && inProgress == null) {
+            return null;
+        }
+
+        final List<TickRegionScheduler.TickTime> allData = new ArrayList<>(this.timeData);
+        if (inProgress != null) {
+            allData.add(inProgress);
+        }
+
+        final long intervalStart = allData.get(0).tickStart();
+        final long intervalEnd = allData.get(allData.size() - 1).tickEnd();
+
+        // to make utilisation accurate, we need to take the total time used over the last interval period -
+        // this means if a tick start before the measurement interval, but ends within the interval, then we
+        // only consider the time it spent ticking inside the interval
+        long totalTimeOverInterval = 0L;
+        long measureStart = endTime - this.interval;
+
+        for (int i = 0, len = allData.size(); i < len; ++i) {
+            final TickRegionScheduler.TickTime time = allData.get(i);
+            if (TimeUtil.compareTimes(time.tickStart(), measureStart) < 0) {
+                final long diff = time.tickEnd() - measureStart;
+                if (diff > 0L) {
+                    totalTimeOverInterval += diff;
+                } // else: the time is entirely out of interval
+            } else {
+                totalTimeOverInterval += time.tickLength();
+            }
+        }
+
+        // we only care about ticks, but because of inbetween tick task execution
+        // there will be data in allData that isn't ticks. But, that data cannot
+        // be ignored since it contributes to utilisation.
+        // So, we will "compact" the data by merging any inbetween tick times
+        // the next tick.
+        // If there is no "next tick", then we will create one.
+        final List<TickInformation> collapsedData = new ArrayList<>();
+        for (int i = 0, len = allData.size(); i < len; ++i) {
+            final List<TickRegionScheduler.TickTime> toCollapse = new ArrayList<>();
+            TickRegionScheduler.TickTime lastTick = null;
+            for (;i < len; ++i) {
+                final TickRegionScheduler.TickTime time = allData.get(i);
+                if (!time.isTickExecution()) {
+                    toCollapse.add(time);
+                    continue;
+                }
+                lastTick = time;
+                break;
+            }
+
+            if (toCollapse.isEmpty()) {
+                // nothing to collapse
+                final TickRegionScheduler.TickTime last = allData.get(i);
+                collapsedData.add(
+                    new TickInformation(
+                        last.differenceFromLastTick(),
+                        last.tickLength(),
+                        last.supportCPUTime() ? last.tickCpuTime() : 0L
+                    )
+                );
+            } else {
+                long totalTickTime = 0L;
+                long totalCpuTime = 0L;
+                for (int k = 0, len2 = collapsedData.size(); k < len2; ++k) {
+                    final TickRegionScheduler.TickTime time = toCollapse.get(k);
+                    totalTickTime += time.tickLength();
+                    totalCpuTime += time.supportCPUTime() ? time.tickCpuTime() : 0L;
+                }
+                if (i < len) {
+                    // we know there is a tick to collapse into
+                    final TickRegionScheduler.TickTime last = allData.get(i);
+                    collapsedData.add(
+                        new TickInformation(
+                            last.differenceFromLastTick(),
+                            last.tickLength() + totalTickTime,
+                            (last.supportCPUTime() ? last.tickCpuTime() : 0L) + totalCpuTime
+                        )
+                    );
+                } else {
+                    // we do not have a tick to collapse into, so we must make one up
+                    // we will assume that the tick is "starting now" and ongoing
+
+                    // compute difference between imaginary tick and last tick
+                    final long differenceBetweenTicks;
+                    if (lastTick != null) {
+                        // we have a last tick, use it
+                        differenceBetweenTicks = lastTick.tickStart();
+                    } else {
+                        // we don't have a last tick, so we must make one up that makes sense
+                        // if the current interval exceeds the max tick time, then use it
+
+                        // Otherwise use the interval length.
+                        // This is how differenceFromLastTick() works on TickTime when there is no previous interval.
+                        differenceBetweenTicks = Math.max(
+                            TickRegionScheduler.TIME_BETWEEN_TICKS, totalTickTime
+                        );
+                    }
+
+                    collapsedData.add(
+                        new TickInformation(
+                            differenceBetweenTicks,
+                            totalTickTime,
+                            totalCpuTime
+                        )
+                    );
+                }
+            }
+        }
+
+
+        final int collectedTicks = collapsedData.size();
+        final long[] tickStartToStartDifferences = new long[collectedTicks];
+        final long[] timePerTickDataRaw = new long[collectedTicks];
+        final long[] missingCPUTimeDataRaw = new long[collectedTicks];
+
+        long totalTimeTicking = 0L;
+
+        int i = 0;
+        for (final TickInformation time : collapsedData) {
+            tickStartToStartDifferences[i] = time.differenceFromLastTick();
+            final long timePerTick = timePerTickDataRaw[i] = time.tickTime();
+            missingCPUTimeDataRaw[i] = Math.max(0L, timePerTick - time.tickTimeCPU());
+
+            ++i;
+
+            totalTimeTicking += timePerTick;
+        }
+
+        Arrays.sort(tickStartToStartDifferences);
+        Arrays.sort(timePerTickDataRaw);
+        Arrays.sort(missingCPUTimeDataRaw);
+
+        // Note: computeSegmentData cannot take start == end
+        final int allStart = 0;
+        final int allEnd = collectedTicks;
+        final int percent95BestStart = 0;
+        final int percent95BestEnd = collectedTicks == 1 ? 1 : (int)(0.95 * collectedTicks);
+        final int percent99BestStart = 0;
+        // (int)(0.99 * collectedTicks) == 0 if collectedTicks = 1, so we need to use 1 to avoid start == end
+        final int percent99BestEnd = collectedTicks == 1 ? 1 : (int)(0.99 * collectedTicks);
+        final int percent1WorstStart = (int)(0.99 * collectedTicks);
+        final int percent1WorstEnd = collectedTicks;
+        final int percent5WorstStart = (int)(0.95 * collectedTicks);
+        final int percent5WorstEnd = collectedTicks;
+
+        final SegmentedAverage tpsData = computeSegmentedAverage(
+            tickStartToStartDifferences,
+            allStart, allEnd,
+            percent99BestStart, percent99BestEnd,
+            percent95BestStart, percent95BestEnd,
+            percent1WorstStart, percent1WorstEnd,
+            percent5WorstStart, percent5WorstEnd,
+            true
+        );
+
+        final SegmentedAverage timePerTickData = computeSegmentedAverage(
+            timePerTickDataRaw,
+            allStart, allEnd,
+            percent99BestStart, percent99BestEnd,
+            percent95BestStart, percent95BestEnd,
+            percent1WorstStart, percent1WorstEnd,
+            percent5WorstStart, percent5WorstEnd,
+            false
+        );
+
+        final SegmentedAverage missingCPUTimeData = computeSegmentedAverage(
+            missingCPUTimeDataRaw,
+            allStart, allEnd,
+            percent99BestStart, percent99BestEnd,
+            percent95BestStart, percent95BestEnd,
+            percent1WorstStart, percent1WorstEnd,
+            percent5WorstStart, percent5WorstEnd,
+            false
+        );
+
+        final double utilisation = (double)totalTimeOverInterval / (double)this.interval;
+
+        return new TickReportData(
+            collectedTicks,
+            intervalStart,
+            intervalEnd,
+            totalTimeTicking,
+            utilisation,
+
+            tpsData,
+            timePerTickData,
+            missingCPUTimeData
+        );
+    }
+
+    public static final record TickReportData(
+        int collectedTicks,
+        long collectedTickIntervalStart,
+        long collectedTickIntervalEnd,
+        long totalTimeTicking,
+        double utilisation,
+
+        SegmentedAverage tpsData,
+        // in ns
+        SegmentedAverage timePerTickData,
+        // in ns
+        SegmentedAverage missingCPUTimeData
+    ) {}
+
+    public static final record SegmentedAverage(
+        SegmentData segmentAll,
+        SegmentData segment99PercentBest,
+        SegmentData segment95PercentBest,
+        SegmentData segment5PercentWorst,
+        SegmentData segment1PercentWorst
+    ) {}
+
+    public static final record SegmentData(
+        int count,
+        double average,
+        double median,
+        double least,
+        double greatest
+    ) {}
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/TickRegionScheduler.java b/src/main/java/io/papermc/paper/threadedregions/TickRegionScheduler.java
new file mode 100644
index 0000000000000000000000000000000000000000..150610d7bf25416dbbde7f003c47da562acc68ba
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/TickRegionScheduler.java
@@ -0,0 +1,565 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool;
+import ca.spottedleaf.concurrentutil.util.TimeUtil;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.util.TickThread;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import org.slf4j.Logger;
+import java.lang.management.ManagementFactory;
+import java.lang.management.ThreadMXBean;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BooleanSupplier;
+
+public final class TickRegionScheduler {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+    private static final ThreadMXBean THREAD_MX_BEAN = ManagementFactory.getThreadMXBean();
+    private static final boolean MEASURE_CPU_TIME;
+    static {
+        MEASURE_CPU_TIME = THREAD_MX_BEAN.isThreadCpuTimeSupported();
+        if (MEASURE_CPU_TIME) {
+            THREAD_MX_BEAN.setThreadCpuTimeEnabled(true);
+        } else {
+            LOGGER.warn("TickRegionScheduler CPU time measurement is not available");
+        }
+    }
+
+    public static final int TICK_RATE = 20;
+    public static final long TIME_BETWEEN_TICKS = 1_000_000_000L / TICK_RATE; // ns
+
+    private final SchedulerThreadPool scheduler;
+
+    public TickRegionScheduler(final int threads) {
+        this.scheduler = new SchedulerThreadPool(threads, new ThreadFactory() {
+            private final AtomicInteger idGenerator = new AtomicInteger();
+
+            @Override
+            public Thread newThread(final Runnable run) {
+                final Thread ret = new TickThreadRunner(run, "Region Scheduler Thread #" + this.idGenerator.getAndIncrement());
+                ret.setUncaughtExceptionHandler(TickRegionScheduler.this::uncaughtException);
+                return ret;
+            }
+        });
+    }
+
+    public int getTotalThreadCount() {
+        return this.scheduler.getThreads().length;
+    }
+
+    private static void setTickingRegion(final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region) {
+        final Thread currThread = Thread.currentThread();
+        if (!(currThread instanceof TickThreadRunner tickThreadRunner)) {
+            throw new IllegalStateException("Must be tick thread runner");
+        }
+        if (region != null && tickThreadRunner.currentTickingRegion != null) {
+            throw new IllegalStateException("Trying to double set ticking region!");
+        }
+        if (region == null && tickThreadRunner.currentTickingRegion == null) {
+            throw new IllegalStateException("Trying to double unset ticking region!");
+        }
+        tickThreadRunner.currentTickingRegion = region;
+        if (region != null) {
+            tickThreadRunner.currentTickingWorldRegionizedData = region.regioniser.world.worldRegionData.get();
+        } else {
+            tickThreadRunner.currentTickingWorldRegionizedData = null;
+        }
+    }
+
+    private static void setTickTask(final SchedulerThreadPool.SchedulableTick task) {
+        final Thread currThread = Thread.currentThread();
+        if (!(currThread instanceof TickThreadRunner tickThreadRunner)) {
+            throw new IllegalStateException("Must be tick thread runner");
+        }
+        if (task != null && tickThreadRunner.currentTickingTask != null) {
+            throw new IllegalStateException("Trying to double set ticking task!");
+        }
+        if (task == null && tickThreadRunner.currentTickingTask == null) {
+            throw new IllegalStateException("Trying to double unset ticking task!");
+        }
+        tickThreadRunner.currentTickingTask = task;
+    }
+
+    /**
+     * Returns the current ticking region, or {@code null} if there is no ticking region.
+     * If this thread is not a TickThread, then returns {@code null}.
+     */
+    public static ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> getCurrentRegion() {
+        final Thread currThread = Thread.currentThread();
+        if (!(currThread instanceof TickThreadRunner tickThreadRunner)) {
+            return RegionShutdownThread.getRegion();
+        }
+        return tickThreadRunner.currentTickingRegion;
+    }
+
+    /**
+     * Returns the current ticking region's world regionised data, or {@code null} if there is no ticking region.
+     * This is a faster alternative to calling the {@link RegionizedData#get()} method.
+     * If this thread is not a TickThread, then returns {@code null}.
+     */
+    public static RegionizedWorldData getCurrentRegionizedWorldData() {
+        final Thread currThread = Thread.currentThread();
+        if (!(currThread instanceof TickThreadRunner tickThreadRunner)) {
+            return RegionShutdownThread.getWorldData();
+        }
+        return tickThreadRunner.currentTickingWorldRegionizedData;
+    }
+
+    /**
+     * Returns the current ticking task, or {@code null} if there is no ticking region.
+     * If this thread is not a TickThread, then returns {@code null}.
+     */
+    public static SchedulerThreadPool.SchedulableTick getCurrentTickingTask() {
+        final Thread currThread = Thread.currentThread();
+        if (!(currThread instanceof TickThreadRunner tickThreadRunner)) {
+            return null;
+        }
+        return tickThreadRunner.currentTickingTask;
+    }
+
+    /**
+     * Schedules the given region
+     * @throws IllegalStateException If the region is already scheduled or is ticking
+     */
+    public void scheduleRegion(final RegionScheduleHandle region) {
+        region.scheduler = this;
+        this.scheduler.schedule(region);
+    }
+
+    /**
+     * Attempts to de-schedule the provided region. If the current region cannot be cancelled for its next tick or task
+     * execution, then it will be cancelled after.
+     */
+    public void descheduleRegion(final RegionScheduleHandle region) {
+        // To avoid acquiring any of the locks the scheduler may be using, we
+        // simply cancel the next action.
+        region.markNonSchedulable();
+    }
+
+    /**
+     * Updates the tick start to the farthest into the future of its current scheduled time and the
+     * provided time.
+     * @return {@code false} if the region was not scheduled or is currently ticking or the specified time is less-than its
+     *                       current start time, {@code true} if the next tick start was adjusted.
+     */
+    public boolean updateTickStartToMax(final RegionScheduleHandle region, final long newStart) {
+        return this.scheduler.updateTickStartToMax(region, newStart);
+    }
+
+    public boolean halt(final boolean sync, final long maxWaitNS) {
+        return this.scheduler.halt(sync, maxWaitNS);
+    }
+
+    void dumpAliveThreadTraces(final String reason) {
+        this.scheduler.dumpAliveThreadTraces(reason);
+    }
+
+    public void setHasTasks(final RegionScheduleHandle region) {
+        this.scheduler.notifyTasks(region);
+    }
+
+    public void init() {
+        this.scheduler.start();
+    }
+
+    private void uncaughtException(final Thread thread, final Throwable thr) {
+        LOGGER.error("Uncaught exception in tick thread \"" + thread.getName() + "\"", thr);
+
+        // prevent further ticks from occurring
+        // we CANNOT sync, because WE ARE ON A SCHEDULER THREAD
+        this.scheduler.halt(false, 0L);
+
+        MinecraftServer.getServer().stopServer();
+    }
+
+    private void regionFailed(final RegionScheduleHandle handle, final boolean executingTasks, final Throwable thr) {
+        // when a region fails, we need to shut down the server gracefully
+
+        // prevent further ticks from occurring
+        // we CANNOT sync, because WE ARE ON A SCHEDULER THREAD
+        this.scheduler.halt(false, 0L);
+
+        final ChunkPos center = handle.region == null ? null : handle.region.region.getCenterChunk();
+        final ServerLevel world = handle.region == null ? null : handle.region.world;
+
+        LOGGER.error("Region #" + (handle.region == null ? -1L : handle.region.id) + " centered at chunk " + center + " in world '" + (world == null ? "null" : world.getWorld().getName()) + "' failed to " + (executingTasks ? "execute tasks" : "tick") + ":", thr);
+
+        MinecraftServer.getServer().stopServer();
+    }
+
+    // By using our own thread object, we can use a field for the current region rather than a ThreadLocal.
+    // This is much faster than a thread local, since the thread local has to use a map lookup.
+    private static final class TickThreadRunner extends TickThread {
+
+        private ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> currentTickingRegion;
+        private RegionizedWorldData currentTickingWorldRegionizedData;
+        private SchedulerThreadPool.SchedulableTick currentTickingTask;
+
+        public TickThreadRunner(final Runnable run, final String name) {
+            super(run, name);
+        }
+    }
+
+    public static abstract class RegionScheduleHandle extends SchedulerThreadPool.SchedulableTick {
+
+        protected long currentTick;
+        protected long lastTickStart;
+
+        protected final TickData tickTimes5s;
+        protected final TickData tickTimes15s;
+        protected final TickData tickTimes1m;
+        protected final TickData tickTimes5m;
+        protected final TickData tickTimes15m;
+        protected TickTime currentTickData;
+        protected Thread currentTickingThread;
+
+        public final TickRegions.TickRegionData region;
+        private final AtomicBoolean cancelled = new AtomicBoolean();
+
+        protected final Schedule tickSchedule;
+
+        private TickRegionScheduler scheduler;
+
+        public RegionScheduleHandle(final TickRegions.TickRegionData region, final long firstStart) {
+            this.currentTick = 0L;
+            this.lastTickStart = SchedulerThreadPool.DEADLINE_NOT_SET;
+            this.tickTimes5s = new TickData(TimeUnit.SECONDS.toNanos(5L));
+            this.tickTimes15s = new TickData(TimeUnit.SECONDS.toNanos(15L));
+            this.tickTimes1m = new TickData(TimeUnit.MINUTES.toNanos(1L));
+            this.tickTimes5m = new TickData(TimeUnit.MINUTES.toNanos(5L));
+            this.tickTimes15m = new TickData(TimeUnit.MINUTES.toNanos(15L));
+            this.region = region;
+
+            this.setScheduledStart(firstStart);
+            this.tickSchedule = new Schedule(firstStart == SchedulerThreadPool.DEADLINE_NOT_SET ? firstStart : firstStart - TIME_BETWEEN_TICKS);
+        }
+
+        /**
+         * Subclasses should call this instead of {@link ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool.SchedulableTick#setScheduledStart(long)}
+         * so that the tick schedule and scheduled start remain synchronised
+         */
+        protected final void updateScheduledStart(final long to) {
+            this.setScheduledStart(to);
+            this.tickSchedule.setLastPeriod(to == SchedulerThreadPool.DEADLINE_NOT_SET ? to : to - TIME_BETWEEN_TICKS);
+        }
+
+        public final void markNonSchedulable() {
+            this.cancelled.set(true);
+        }
+
+        public final boolean isMarkedAsNonSchedulable() {
+            return this.cancelled.get();
+        }
+
+        protected abstract boolean tryMarkTicking();
+
+        protected abstract boolean markNotTicking();
+
+        protected abstract void tickRegion(final int tickCount, final long startTime, final long scheduledEnd);
+
+        protected abstract boolean runRegionTasks(final BooleanSupplier canContinue);
+
+        protected abstract boolean hasIntermediateTasks();
+
+        @Override
+        public final boolean hasTasks() {
+            return this.hasIntermediateTasks();
+        }
+
+        @Override
+        public final Boolean runTasks(final BooleanSupplier canContinue) {
+            if (this.cancelled.get()) {
+                return null;
+            }
+
+            final long cpuStart = MEASURE_CPU_TIME ? THREAD_MX_BEAN.getCurrentThreadCpuTime() : 0L;
+            final long tickStart = System.nanoTime();
+
+            if (!this.tryMarkTicking()) {
+                if (!this.cancelled.get()) {
+                    throw new IllegalStateException("Scheduled region should be acquirable");
+                }
+                // region was killed
+                return null;
+            }
+
+            TickRegionScheduler.setTickTask(this);
+            if (this.region != null) {
+                TickRegionScheduler.setTickingRegion(this.region.region);
+            }
+
+            synchronized (this) {
+                this.currentTickData = new TickTime(
+                    SchedulerThreadPool.DEADLINE_NOT_SET, SchedulerThreadPool.DEADLINE_NOT_SET, tickStart, cpuStart,
+                    SchedulerThreadPool.DEADLINE_NOT_SET, SchedulerThreadPool.DEADLINE_NOT_SET, MEASURE_CPU_TIME,
+                    false
+                );
+                this.currentTickingThread = Thread.currentThread();
+            }
+
+            final boolean ret;
+            try {
+                ret = this.runRegionTasks(() -> {
+                    return !RegionScheduleHandle.this.cancelled.get() && canContinue.getAsBoolean();
+                });
+            } catch (final Throwable thr) {
+                this.scheduler.regionFailed(this, true, thr);
+                if (thr instanceof ThreadDeath) {
+                    throw (ThreadDeath)thr;
+                }
+                // don't release region for another tick
+                return null;
+            } finally {
+                final long tickEnd = System.nanoTime();
+                final long cpuEnd = MEASURE_CPU_TIME ? THREAD_MX_BEAN.getCurrentThreadCpuTime() : 0L;
+
+                final TickTime time = new TickTime(
+                    SchedulerThreadPool.DEADLINE_NOT_SET, SchedulerThreadPool.DEADLINE_NOT_SET,
+                    tickStart, cpuStart, tickEnd, cpuEnd, MEASURE_CPU_TIME, false
+                );
+
+                this.addTickTime(time);
+                TickRegionScheduler.setTickTask(null);
+                if (this.region != null) {
+                    TickRegionScheduler.setTickingRegion(null);
+                }
+            }
+
+            return !this.markNotTicking() || this.cancelled.get() ? null : Boolean.valueOf(ret);
+        }
+
+        @Override
+        public final boolean runTick() {
+            // Remember, we are supposed use setScheduledStart if we return true here, otherwise
+            // the scheduler will try to schedule for the same time.
+            if (this.cancelled.get()) {
+                return false;
+            }
+
+            final long cpuStart = MEASURE_CPU_TIME ? THREAD_MX_BEAN.getCurrentThreadCpuTime() : 0L;
+            final long tickStart = System.nanoTime();
+
+            // use max(), don't assume that tickStart >= scheduledStart
+            final int tickCount = Math.max(1, this.tickSchedule.getPeriodsAhead(TIME_BETWEEN_TICKS, tickStart));
+
+            if (!this.tryMarkTicking()) {
+                if (!this.cancelled.get()) {
+                    throw new IllegalStateException("Scheduled region should be acquirable");
+                }
+                // region was killed
+                return false;
+            }
+            if (this.cancelled.get()) {
+                this.markNotTicking();
+                // region should be killed
+                return false;
+            }
+
+            TickRegionScheduler.setTickTask(this);
+            if (this.region != null) {
+                TickRegionScheduler.setTickingRegion(this.region.region);
+            }
+            this.incrementTickCount();
+            final long lastTickStart = this.lastTickStart;
+            this.lastTickStart = tickStart;
+
+            final long scheduledStart = this.getScheduledStart();
+            final long scheduledEnd = scheduledStart + TIME_BETWEEN_TICKS;
+
+            synchronized (this) {
+                this.currentTickData = new TickTime(
+                    lastTickStart, scheduledStart, tickStart, cpuStart,
+                    SchedulerThreadPool.DEADLINE_NOT_SET, SchedulerThreadPool.DEADLINE_NOT_SET, MEASURE_CPU_TIME,
+                    true
+                );
+                this.currentTickingThread = Thread.currentThread();
+            }
+
+            try {
+                // next start isn't updated until the end of this tick
+                this.tickRegion(tickCount, tickStart, scheduledEnd);
+            } catch (final Throwable thr) {
+                this.scheduler.regionFailed(this, false, thr);
+                if (thr instanceof ThreadDeath) {
+                    throw (ThreadDeath)thr;
+                }
+                // regionFailed will schedule a shutdown, so we should avoid letting this region tick further
+                return false;
+            } finally {
+                final long tickEnd = System.nanoTime();
+                final long cpuEnd = MEASURE_CPU_TIME ? THREAD_MX_BEAN.getCurrentThreadCpuTime() : 0L;
+
+                // in order to ensure all regions get their chance at scheduling, we have to ensure that regions
+                // that exceed the max tick time are not always prioritised over everything else. Thus, we use the greatest
+                // of the current time and "ideal" next tick start.
+                this.tickSchedule.advanceBy(tickCount, TIME_BETWEEN_TICKS);
+                this.setScheduledStart(TimeUtil.getGreatestTime(tickEnd, this.tickSchedule.getDeadline(TIME_BETWEEN_TICKS)));
+
+                final TickTime time = new TickTime(
+                    lastTickStart, scheduledStart, tickStart, cpuStart, tickEnd, cpuEnd, MEASURE_CPU_TIME, true
+                );
+
+                this.addTickTime(time);
+                TickRegionScheduler.setTickTask(null);
+                if (this.region != null) {
+                    TickRegionScheduler.setTickingRegion(null);
+                }
+            }
+
+            // Only AFTER updating the tickStart
+            return this.markNotTicking() && !this.cancelled.get();
+        }
+
+        /**
+         * Only safe to call if this tick data matches the current ticking region.
+         */
+        protected void addTickTime(final TickTime time) {
+            synchronized (this) {
+                this.currentTickData = null;
+                this.currentTickingThread = null;
+                this.tickTimes5s.addDataFrom(time);
+                this.tickTimes15s.addDataFrom(time);
+                this.tickTimes1m.addDataFrom(time);
+                this.tickTimes5m.addDataFrom(time);
+                this.tickTimes15m.addDataFrom(time);
+            }
+        }
+
+        private TickTime adjustCurrentTickData(final long tickEnd) {
+            final TickTime currentTickData = this.currentTickData;
+            if (currentTickData == null) {
+                return null;
+            }
+
+            final long cpuEnd = MEASURE_CPU_TIME ? THREAD_MX_BEAN.getThreadCpuTime(this.currentTickingThread.getId()) : 0L;
+
+            return new TickTime(
+                currentTickData.previousTickStart(), currentTickData.scheduledTickStart(),
+                currentTickData.tickStart(), currentTickData.tickStartCPU(),
+                tickEnd, cpuEnd,
+                MEASURE_CPU_TIME, currentTickData.isTickExecution()
+            );
+        }
+
+        public final TickData.TickReportData getTickReport5s(final long currTime) {
+            synchronized (this) {
+                return this.tickTimes5s.generateTickReport(this.adjustCurrentTickData(currTime), currTime);
+            }
+        }
+
+        public final TickData.TickReportData getTickReport15s(final long currTime) {
+            synchronized (this) {
+                return this.tickTimes15s.generateTickReport(this.adjustCurrentTickData(currTime), currTime);
+            }
+        }
+
+        public final TickData.TickReportData getTickReport1m(final long currTime) {
+            synchronized (this) {
+                return this.tickTimes1m.generateTickReport(this.adjustCurrentTickData(currTime), currTime);
+            }
+        }
+
+        public final TickData.TickReportData getTickReport5m(final long currTime) {
+            synchronized (this) {
+                return this.tickTimes5m.generateTickReport(this.adjustCurrentTickData(currTime), currTime);
+            }
+        }
+
+        public final TickData.TickReportData getTickReport15m(final long currTime) {
+            synchronized (this) {
+                return this.tickTimes15m.generateTickReport(this.adjustCurrentTickData(currTime), currTime);
+            }
+        }
+
+        /**
+         * Only safe to call if this tick data matches the current ticking region.
+         */
+        private void incrementTickCount() {
+            ++this.currentTick;
+        }
+
+        /**
+         * Only safe to call if this tick data matches the current ticking region.
+         */
+        public final long getCurrentTick() {
+            return this.currentTick;
+        }
+
+        protected final void setCurrentTick(final long value) {
+            this.currentTick = value;
+        }
+    }
+
+    // All time units are in nanoseconds.
+    public static final record TickTime(
+        long previousTickStart,
+        long scheduledTickStart,
+        long tickStart,
+        long tickStartCPU,
+        long tickEnd,
+        long tickEndCPU,
+        boolean supportCPUTime,
+        boolean isTickExecution
+    ) {
+        /**
+         * The difference between the start tick time and the scheduled start tick time. This value is
+         * < 0 if the tick started before the scheduled tick time.
+         * Only valid when {@link #isTickExecution()} is {@code true}.
+         */
+        public final long startOvershoot() {
+            return this.tickStart - this.scheduledTickStart;
+        }
+
+        /**
+         * The difference from the end tick time and the start tick time. Always >= 0 (unless nanoTime is just wrong).
+         */
+        public final long tickLength() {
+            return this.tickEnd - this.tickStart;
+        }
+
+        /**
+         * The total CPU time from the start tick time to the end tick time. Generally should be equal to the tickLength,
+         * unless there is CPU starvation or the tick thread was blocked by I/O or other tasks. Returns Long.MIN_VALUE
+         * if CPU time measurement is not supported.
+         */
+        public final long tickCpuTime() {
+            if (!this.supportCPUTime()) {
+                return Long.MIN_VALUE;
+            }
+            return this.tickEndCPU - this.tickStartCPU;
+        }
+
+        /**
+         * The difference in time from the start of the last tick to the start of the current tick. If there is no
+         * last tick, then this value is max(TIME_BETWEEN_TICKS, tickLength).
+         * Only valid when {@link #isTickExecution()} is {@code true}.
+         */
+        public final long differenceFromLastTick() {
+            if (this.hasLastTick()) {
+                return this.tickStart - this.previousTickStart;
+            }
+            return Math.max(TIME_BETWEEN_TICKS, this.tickLength());
+        }
+
+        /**
+         * Returns whether there was a tick that occurred before this one.
+         * Only valid when {@link #isTickExecution()} is {@code true}.
+         */
+        public boolean hasLastTick() {
+            return this.previousTickStart != SchedulerThreadPool.DEADLINE_NOT_SET;
+        }
+
+        /*
+         * Remember, this is the expected behavior of the following:
+         *
+         * MSPT: Time per tick. This does not include overshoot time, just the tickLength().
+         *
+         * TPS: The number of ticks per second. It should be ticks / (sum of differenceFromLastTick).
+         */
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/TickRegions.java b/src/main/java/io/papermc/paper/threadedregions/TickRegions.java
index d5d39e9c1f326e91010237b0db80d527ac52f4d6..924ade31b788b161a7c8f587504b2fc86932a2ee 100644
--- a/src/main/java/io/papermc/paper/threadedregions/TickRegions.java
+++ b/src/main/java/io/papermc/paper/threadedregions/TickRegions.java
@@ -1,9 +1,409 @@
 package io.papermc.paper.threadedregions;
 
-// placeholder class for Folia
-public class TickRegions {
+import ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool;
+import ca.spottedleaf.concurrentutil.util.TimeUtil;
+import com.mojang.logging.LogUtils;
+import io.papermc.paper.chunk.system.scheduling.ChunkHolderManager;
+import io.papermc.paper.configuration.GlobalConfiguration;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceMap;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.Reference2ReferenceMap;
+import it.unimi.dsi.fastutil.objects.Reference2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import org.slf4j.Logger;
+import java.util.Iterator;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.function.BooleanSupplier;
+
+public final class TickRegions implements ThreadedRegionizer.RegionCallbacks<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+    private static int regionShift = 31;
 
     public static int getRegionChunkShift() {
-        return 4;
+        return regionShift;
+    }
+
+    private static boolean initialised;
+    private static TickRegionScheduler scheduler;
+
+    public static TickRegionScheduler getScheduler() {
+        return scheduler;
+    }
+
+    public static void init(final GlobalConfiguration.ThreadedRegions config) {
+        if (initialised) {
+            return;
+        }
+        initialised = true;
+        int gridExponent = config.gridExponent;
+        gridExponent = Math.max(0, gridExponent);
+        gridExponent = Math.min(31, gridExponent);
+        regionShift = gridExponent;
+
+        int tickThreads;
+        if (config.threads <= 0) {
+            tickThreads = Runtime.getRuntime().availableProcessors() / 2;
+            if (tickThreads <= 4) {
+                tickThreads = 1;
+            } else {
+                tickThreads =  tickThreads / 4;
+            }
+        } else {
+            tickThreads = config.threads;
+        }
+
+        scheduler = new TickRegionScheduler(tickThreads);
+        LOGGER.info("Regionised ticking is enabled with " + tickThreads + " tick threads");
+    }
+
+    @Override
+    public TickRegionData createNewData(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        return new TickRegionData(region);
+    }
+
+    @Override
+    public TickRegionSectionData createNewSectionData(final int sectionX, final int sectionZ, final int sectionShift) {
+        return null;
+    }
+
+    @Override
+    public void onRegionCreate(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        final TickRegionData data = region.getData();
+        // post-region merge/split regioninfo update
+        data.getRegionStats().updateFrom(data.getOrCreateRegionizedData(data.world.worldRegionData));
+    }
+
+    @Override
+    public void onRegionDestroy(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        // nothing for now
+    }
+
+    @Override
+    public void onRegionActive(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        final TickRegionData data = region.getData();
+
+        data.tickHandle.checkInitialSchedule();
+        scheduler.scheduleRegion(data.tickHandle);
+    }
+
+    @Override
+    public void onRegionInactive(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        final TickRegionData data = region.getData();
+
+        scheduler.descheduleRegion(data.tickHandle);
+        // old handle cannot be scheduled anymore, copy to a new handle
+        data.tickHandle = data.tickHandle.copy();
+    }
+
+    @Override
+    public void preMerge(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> from,
+                         final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> into) {
+
+    }
+
+    @Override
+    public void preSplit(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> from,
+                         final java.util.List<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>> into) {
+
+    }
+
+    public static final class TickRegionSectionData implements ThreadedRegionizer.ThreadedRegionSectionData {}
+
+    public static final class RegionStats {
+
+        private final AtomicInteger entityCount = new AtomicInteger();
+        private final AtomicInteger playerCount = new AtomicInteger();
+        private final AtomicInteger chunkCount = new AtomicInteger();
+
+        public int getEntityCount() {
+            return this.entityCount.get();
+        }
+
+        public int getPlayerCount() {
+            return this.playerCount.get();
+        }
+
+        public int getChunkCount() {
+            return this.chunkCount.get();
+        }
+
+        void updateFrom(final RegionizedWorldData data) {
+            this.entityCount.setRelease(data == null ? 0 : data.getEntityCount());
+            this.playerCount.setRelease(data == null ? 0 : data.getPlayerCount());
+            this.chunkCount.setRelease(data == null ? 0 : data.getChunkCount());
+        }
+
+        static void updateCurrentRegion() {
+            TickRegionScheduler.getCurrentRegion().getData().getRegionStats().updateFrom(TickRegionScheduler.getCurrentRegionizedWorldData());
+        }
+    }
+
+    public static final class TickRegionData implements ThreadedRegionizer.ThreadedRegionData<TickRegionData, TickRegionSectionData> {
+
+        private static final AtomicLong ID_GENERATOR = new AtomicLong();
+        /** Never 0L, since 0L is reserved for global region. */
+        public final long id = ID_GENERATOR.incrementAndGet();
+
+        public final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region;
+        public final ServerLevel world;
+
+        // generic regionised data
+        private final Reference2ReferenceOpenHashMap<RegionizedData<?>, Object> regionizedData = new Reference2ReferenceOpenHashMap<>();
+
+        // tick data
+        private ConcreteRegionTickHandle tickHandle = new ConcreteRegionTickHandle(this, SchedulerThreadPool.DEADLINE_NOT_SET);
+
+        // queue data
+        private final RegionizedTaskQueue.RegionTaskQueueData taskQueueData;
+
+        // chunk holder manager data
+        private final ChunkHolderManager.HolderManagerRegionData holderManagerRegionData = new ChunkHolderManager.HolderManagerRegionData();
+
+        // async-safe read-only region data
+        private final RegionStats regionStats;
+
+        private TickRegionData(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+            this.region = region;
+            this.world = region.regioniser.world;
+            this.taskQueueData = new RegionizedTaskQueue.RegionTaskQueueData(this.world.taskQueueRegionData);
+            this.regionStats = new RegionStats();
+        }
+
+        public RegionStats getRegionStats() {
+            return this.regionStats;
+        }
+
+        public RegionizedTaskQueue.RegionTaskQueueData getTaskQueueData() {
+            return this.taskQueueData;
+        }
+
+        // the value returned can be invalidated at any time, except when the caller
+        // is ticking this region
+        public TickRegionScheduler.RegionScheduleHandle getRegionSchedulingHandle() {
+            return this.tickHandle;
+        }
+
+        public long getCurrentTick() {
+            return this.tickHandle.getCurrentTick();
+        }
+
+        public ChunkHolderManager.HolderManagerRegionData getHolderManagerRegionData() {
+            return this.holderManagerRegionData;
+        }
+
+        <T> T getRegionizedData(final RegionizedData<T> regionizedData) {
+            return (T)this.regionizedData.get(regionizedData);
+        }
+
+        <T> T getOrCreateRegionizedData(final RegionizedData<T> regionizedData) {
+            T ret = (T)this.regionizedData.get(regionizedData);
+
+            if (ret != null) {
+                return ret;
+            }
+
+            ret = regionizedData.createNewValue();
+            this.regionizedData.put(regionizedData, ret);
+
+            return ret;
+        }
+
+        @Override
+        public void split(final ThreadedRegionizer<TickRegionData, TickRegionSectionData> regioniser,
+                          final Long2ReferenceOpenHashMap<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>> into,
+                          final ReferenceOpenHashSet<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>> regions) {
+            final int shift = regioniser.sectionChunkShift;
+
+            // tick data
+            // note: here it is OK force us to access tick handle, as this region is owned (and thus not scheduled),
+            // and the other regions to split into are not scheduled yet.
+            for (final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region : regions) {
+                final TickRegionData data = region.getData();
+                data.tickHandle.copyDeadlineAndTickCount(this.tickHandle);
+            }
+
+            // generic regionised data
+            for (final Iterator<Reference2ReferenceMap.Entry<RegionizedData<?>, Object>> dataIterator = this.regionizedData.reference2ReferenceEntrySet().fastIterator();
+                 dataIterator.hasNext();) {
+                final Reference2ReferenceMap.Entry<RegionizedData<?>, Object> regionDataEntry = dataIterator.next();
+                final RegionizedData<?> data = regionDataEntry.getKey();
+                final Object from = regionDataEntry.getValue();
+
+                final ReferenceOpenHashSet<Object> dataSet = new ReferenceOpenHashSet<>(regions.size(), 0.75f);
+
+                for (final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region : regions) {
+                    dataSet.add(region.getData().getOrCreateRegionizedData(data));
+                }
+
+                final Long2ReferenceOpenHashMap<Object> regionToData = new Long2ReferenceOpenHashMap<>(into.size(), 0.75f);
+
+                for (final Iterator<Long2ReferenceMap.Entry<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>>> regionIterator = into.long2ReferenceEntrySet().fastIterator();
+                     regionIterator.hasNext();) {
+                    final Long2ReferenceMap.Entry<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>> entry = regionIterator.next();
+                    final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region = entry.getValue();
+                    final Object to = region.getData().getOrCreateRegionizedData(data);
+
+                    regionToData.put(entry.getLongKey(), to);
+                }
+
+                ((RegionizedData<Object>)data).getCallback().split(from, shift, regionToData, dataSet);
+            }
+
+            // chunk holder manager data
+            {
+                final ReferenceOpenHashSet<ChunkHolderManager.HolderManagerRegionData> dataSet = new ReferenceOpenHashSet<>(regions.size(), 0.75f);
+
+                for (final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region : regions) {
+                    dataSet.add(region.getData().holderManagerRegionData);
+                }
+
+                final Long2ReferenceOpenHashMap<ChunkHolderManager.HolderManagerRegionData> regionToData = new Long2ReferenceOpenHashMap<>(into.size(), 0.75f);
+
+                for (final Iterator<Long2ReferenceMap.Entry<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>>> regionIterator = into.long2ReferenceEntrySet().fastIterator();
+                     regionIterator.hasNext();) {
+                    final Long2ReferenceMap.Entry<ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData>> entry = regionIterator.next();
+                    final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> region = entry.getValue();
+                    final ChunkHolderManager.HolderManagerRegionData to = region.getData().holderManagerRegionData;
+
+                    regionToData.put(entry.getLongKey(), to);
+                }
+
+                this.holderManagerRegionData.split(shift, regionToData, dataSet);
+            }
+
+            // task queue
+            this.taskQueueData.split(regioniser, into);
+        }
+
+        @Override
+        public void mergeInto(final ThreadedRegionizer.ThreadedRegion<TickRegionData, TickRegionSectionData> into) {
+            // Note: merge target is always a region being released from ticking
+            final TickRegionData data = into.getData();
+            final long currentTickTo = data.getCurrentTick();
+            final long currentTickFrom = this.getCurrentTick();
+
+            // here we can access tickHandle because the target (into) is the region being released, so it is
+            // not actually scheduled
+            // there's not really a great solution to the tick problem, no matter what it'll be messed up
+            // we will pick the greatest time delay so that tps will not exceed TICK_RATE
+            data.tickHandle.updateSchedulingToMax(this.tickHandle);
+
+            // generic regionised data
+            final long fromTickOffset = currentTickTo - currentTickFrom; // see merge jd
+            for (final Iterator<Reference2ReferenceMap.Entry<RegionizedData<?>, Object>> iterator = this.regionizedData.reference2ReferenceEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Reference2ReferenceMap.Entry<RegionizedData<?>, Object> entry = iterator.next();
+                final RegionizedData<?> regionizedData = entry.getKey();
+                final Object from = entry.getValue();
+                final Object to = into.getData().getOrCreateRegionizedData(regionizedData);
+
+                ((RegionizedData<Object>)regionizedData).getCallback().merge(from, to, fromTickOffset);
+            }
+
+            // chunk holder manager data
+            this.holderManagerRegionData.merge(into.getData().holderManagerRegionData, fromTickOffset);
+
+            // task queue
+            this.taskQueueData.mergeInto(data.taskQueueData);
+        }
+    }
+
+    private static final class ConcreteRegionTickHandle extends TickRegionScheduler.RegionScheduleHandle {
+
+        private final TickRegionData region;
+
+        private ConcreteRegionTickHandle(final TickRegionData region, final long start) {
+            super(region, start);
+            this.region = region;
+        }
+
+        private ConcreteRegionTickHandle copy() {
+            final ConcreteRegionTickHandle ret = new ConcreteRegionTickHandle(this.region, this.getScheduledStart());
+
+            ret.currentTick = this.currentTick;
+            ret.lastTickStart = this.lastTickStart;
+            ret.tickSchedule.setLastPeriod(this.tickSchedule.getLastPeriod());
+
+            return ret;
+        }
+
+        private void updateSchedulingToMax(final ConcreteRegionTickHandle from) {
+            if (from.getScheduledStart() == SchedulerThreadPool.DEADLINE_NOT_SET) {
+                return;
+            }
+
+            if (this.getScheduledStart() == SchedulerThreadPool.DEADLINE_NOT_SET) {
+                this.updateScheduledStart(from.getScheduledStart());
+                return;
+            }
+
+            this.updateScheduledStart(TimeUtil.getGreatestTime(from.getScheduledStart(), this.getScheduledStart()));
+        }
+
+        private void copyDeadlineAndTickCount(final ConcreteRegionTickHandle from) {
+            this.currentTick = from.currentTick;
+
+            if (from.getScheduledStart() == SchedulerThreadPool.DEADLINE_NOT_SET) {
+                return;
+            }
+
+            this.tickSchedule.setLastPeriod(from.tickSchedule.getLastPeriod());
+            this.setScheduledStart(from.getScheduledStart());
+        }
+
+        private void checkInitialSchedule() {
+            if (this.getScheduledStart() == SchedulerThreadPool.DEADLINE_NOT_SET) {
+                this.updateScheduledStart(System.nanoTime() + TickRegionScheduler.TIME_BETWEEN_TICKS);
+            }
+        }
+
+        @Override
+        protected boolean tryMarkTicking() {
+            return this.region.region.tryMarkTicking(ConcreteRegionTickHandle.this::isMarkedAsNonSchedulable);
+        }
+
+        @Override
+        protected boolean markNotTicking() {
+            return this.region.region.markNotTicking();
+        }
+
+        @Override
+        protected void tickRegion(final int tickCount, final long startTime, final long scheduledEnd) {
+            MinecraftServer.getServer().tickServer(startTime, scheduledEnd, TimeUnit.MILLISECONDS.toMillis(10L), this.region);
+        }
+
+        @Override
+        protected boolean runRegionTasks(final BooleanSupplier canContinue) {
+            final RegionizedTaskQueue.RegionTaskQueueData queue = this.region.taskQueueData;
+
+            boolean processedChunkTask = false;
+
+            boolean executeChunkTask = true;
+            boolean executeTickTask = true;
+            do {
+                if (executeTickTask) {
+                    executeTickTask = queue.executeTickTask();
+                }
+                if (executeChunkTask) {
+                    processedChunkTask |= (executeChunkTask = queue.executeChunkTask());
+                }
+            } while ((executeChunkTask | executeTickTask) && canContinue.getAsBoolean());
+
+            if (processedChunkTask) {
+                // if we processed any chunk tasks, try to process ticket level updates for full status changes
+                this.region.world.chunkTaskScheduler.chunkHolderManager.processTicketUpdates();
+            }
+            return true;
+        }
+
+        @Override
+        protected boolean hasIntermediateTasks() {
+            return this.region.taskQueueData.hasTasks();
+        }
     }
 }
diff --git a/src/main/java/io/papermc/paper/threadedregions/commands/CommandServerHealth.java b/src/main/java/io/papermc/paper/threadedregions/commands/CommandServerHealth.java
new file mode 100644
index 0000000000000000000000000000000000000000..3bcb1dc98c61e025874cc9e008faa722581a530c
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/commands/CommandServerHealth.java
@@ -0,0 +1,355 @@
+package io.papermc.paper.threadedregions.commands;
+
+import io.papermc.paper.threadedregions.RegionizedServer;
+import io.papermc.paper.threadedregions.RegionizedWorldData;
+import io.papermc.paper.threadedregions.ThreadedRegionizer;
+import io.papermc.paper.threadedregions.TickData;
+import io.papermc.paper.threadedregions.TickRegionScheduler;
+import io.papermc.paper.threadedregions.TickRegions;
+import it.unimi.dsi.fastutil.doubles.DoubleArrayList;
+import it.unimi.dsi.fastutil.objects.ObjectObjectImmutablePair;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.TextComponent;
+import net.kyori.adventure.text.event.ClickEvent;
+import net.kyori.adventure.text.event.HoverEvent;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.text.format.TextColor;
+import net.kyori.adventure.text.format.TextDecoration;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Player;
+import java.text.DecimalFormat;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+
+public final class CommandServerHealth extends Command {
+
+    private static final ThreadLocal<DecimalFormat> TWO_DECIMAL_PLACES = ThreadLocal.withInitial(() -> {
+        return new DecimalFormat("#,##0.00");
+    });
+    private static final ThreadLocal<DecimalFormat> ONE_DECIMAL_PLACES = ThreadLocal.withInitial(() -> {
+        return new DecimalFormat("#,##0.0");
+    });
+    private static final ThreadLocal<DecimalFormat> NO_DECIMAL_PLACES = ThreadLocal.withInitial(() -> {
+        return new DecimalFormat("#,##0");
+    });
+
+    private static final TextColor HEADER = TextColor.color(79, 164, 240);
+    private static final TextColor PRIMARY = TextColor.color(48, 145, 237);
+    private static final TextColor SECONDARY = TextColor.color(104, 177, 240);
+    private static final TextColor INFORMATION = TextColor.color(145, 198, 243);
+    private static final TextColor LIST = TextColor.color(33, 97, 188);
+
+    public CommandServerHealth() {
+        super("tps");
+        this.setUsage("/<command> [server/region] [lowest regions to display]");
+        this.setDescription("Reports information about server health.");
+        this.setPermission("bukkit.command.tps");
+    }
+
+    private static Component formatRegionInfo(final String prefix, final double util, final double mspt, final double tps,
+                                              final boolean newline) {
+        return Component.text()
+            .append(Component.text(prefix, PRIMARY, TextDecoration.BOLD))
+            .append(Component.text(ONE_DECIMAL_PLACES.get().format(util * 100.0), CommandUtil.getUtilisationColourRegion(util)))
+            .append(Component.text("% util at ", PRIMARY))
+            .append(Component.text(TWO_DECIMAL_PLACES.get().format(mspt), CommandUtil.getColourForMSPT(mspt)))
+            .append(Component.text(" MSPT at ", PRIMARY))
+            .append(Component.text(TWO_DECIMAL_PLACES.get().format(tps), CommandUtil.getColourForTPS(tps)))
+            .append(Component.text(" TPS" + (newline ? "\n" : ""), PRIMARY))
+            .build();
+    }
+
+    private static Component formatRegionStats(final TickRegions.RegionStats stats, final boolean newline) {
+        return Component.text()
+            .append(Component.text("Chunks: ", PRIMARY))
+            .append(Component.text(NO_DECIMAL_PLACES.get().format((long)stats.getChunkCount()), INFORMATION))
+            .append(Component.text(" Players: ", PRIMARY))
+            .append(Component.text(NO_DECIMAL_PLACES.get().format((long)stats.getPlayerCount()), INFORMATION))
+            .append(Component.text(" Entities: ", PRIMARY))
+            .append(Component.text(NO_DECIMAL_PLACES.get().format((long)stats.getEntityCount()) + (newline ? "\n" : ""), INFORMATION))
+            .build();
+    }
+
+    private static boolean executeRegion(final CommandSender sender, final String commandLabel, final String[] args) {
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            sender.sendMessage(Component.text("You are not in a region currently", NamedTextColor.RED));
+            return true;
+        }
+
+        final long currTime = System.nanoTime();
+
+        final TickData.TickReportData report15s = region.getData().getRegionSchedulingHandle().getTickReport15s(currTime);
+        final TickData.TickReportData report1m = region.getData().getRegionSchedulingHandle().getTickReport1m(currTime);
+
+        final ServerLevel world = region.regioniser.world;
+        final ChunkPos chunkCenter = region.getCenterChunk();
+        final int centerBlockX = ((chunkCenter.x << 4) | 7);
+        final int centerBlockZ = ((chunkCenter.z << 4) | 7);
+
+        final double util15s = report15s.utilisation();
+        final double tps15s = report15s.tpsData().segmentAll().average();
+        final double mspt15s = report15s.timePerTickData().segmentAll().average() / 1.0E6;
+
+        final double util1m = report1m.utilisation();
+        final double tps1m = report1m.tpsData().segmentAll().average();
+        final double mspt1m = report1m.timePerTickData().segmentAll().average() / 1.0E6;
+
+        final int yLoc = 80;
+        final String location = "[w:'" + world.getWorld().getName() + "'," + centerBlockX + "," + yLoc + "," + centerBlockZ + "]";
+
+        final Component line = Component.text()
+            .append(Component.text("Region around block ", PRIMARY))
+            .append(Component.text(location, INFORMATION))
+            .append(Component.text(":\n", PRIMARY))
+
+            .append(
+                formatRegionInfo("15s: ", util15s, mspt15s, tps15s, true)
+            )
+            .append(
+                formatRegionInfo("1m: ", util1m, mspt1m, tps1m, true)
+            )
+            .append(
+                formatRegionStats(region.getData().getRegionStats(), false)
+            )
+
+            .build();
+
+        sender.sendMessage(line);
+
+        return true;
+    }
+
+    private static boolean executeServer(final CommandSender sender, final String commandLabel, final String[] args) {
+        final int lowestRegionsCount;
+        if (args.length < 2) {
+            lowestRegionsCount = 3;
+        } else {
+            try {
+                lowestRegionsCount = Integer.parseInt(args[1]);
+            } catch (final NumberFormatException ex) {
+                sender.sendMessage(Component.text("Highest utilisation count '" + args[1] + "' must be an integer", NamedTextColor.RED));
+                return true;
+            }
+        }
+
+        final List<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>> regions =
+            new ArrayList<>();
+
+        for (final World bukkitWorld : Bukkit.getWorlds()) {
+            final ServerLevel world = ((CraftWorld)bukkitWorld).getHandle();
+            world.regioniser.computeForAllRegions(regions::add);
+        }
+
+        final double minTps;
+        final double medianTps;
+        final double maxTps;
+        double totalUtil = 0.0;
+
+        final DoubleArrayList tpsByRegion = new DoubleArrayList();
+        final List<TickData.TickReportData> reportsByRegion = new ArrayList<>();
+        final int maxThreadCount = TickRegions.getScheduler().getTotalThreadCount();
+
+        final long currTime = System.nanoTime();
+        final TickData.TickReportData globalTickReport = RegionizedServer.getGlobalTickData().getTickReport15s(currTime);
+
+        for (final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region : regions) {
+            final TickData.TickReportData report = region.getData().getRegionSchedulingHandle().getTickReport15s(currTime);
+            tpsByRegion.add(report == null ? 20.0 : report.tpsData().segmentAll().average());
+            reportsByRegion.add(report);
+            totalUtil += (report == null ? 0.0 : report.utilisation());
+        }
+
+        totalUtil += globalTickReport.utilisation();
+
+        tpsByRegion.sort(null);
+        if (!tpsByRegion.isEmpty()) {
+            minTps = tpsByRegion.getDouble(0);
+            maxTps = tpsByRegion.getDouble(tpsByRegion.size() - 1);
+
+            final int middle = tpsByRegion.size() >> 1;
+            if ((tpsByRegion.size() & 1) == 0) {
+                // even, average the two middle points
+                medianTps = (tpsByRegion.getDouble(middle - 1) + tpsByRegion.getDouble(middle)) / 2.0;
+            } else {
+                // odd, can just grab middle
+                medianTps = tpsByRegion.getDouble(middle);
+            }
+        } else {
+            // no regions = green
+            minTps = medianTps = maxTps = 20.0;
+        }
+
+        final List<ObjectObjectImmutablePair<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, TickData.TickReportData>>
+            regionsBelowThreshold = new ArrayList<>();
+
+        for (int i = 0, len = regions.size(); i < len; ++i) {
+            final TickData.TickReportData report = reportsByRegion.get(i);
+
+            regionsBelowThreshold.add(new ObjectObjectImmutablePair<>(regions.get(i), report));
+        }
+
+        regionsBelowThreshold.sort((p1, p2) -> {
+            final TickData.TickReportData report1 = p1.right();
+            final TickData.TickReportData report2 = p2.right();
+            final double util1 = report1 == null ? 0.0 : report1.utilisation();
+            final double util2 = report2 == null ? 0.0 : report2.utilisation();
+
+            // we want the largest first
+            return Double.compare(util2, util1);
+        });
+
+        final TextComponent.Builder lowestRegionsBuilder = Component.text();
+
+        if (sender instanceof Player) {
+            lowestRegionsBuilder.append(Component.text(" Click to teleport\n", SECONDARY));
+        }
+        for (int i = 0, len = Math.min(lowestRegionsCount, regionsBelowThreshold.size()); i < len; ++i) {
+            final ObjectObjectImmutablePair<ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, TickData.TickReportData>
+                pair = regionsBelowThreshold.get(i);
+
+            final TickData.TickReportData report = pair.right();
+            final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+                pair.left();
+
+            if (report == null) {
+                // skip regions with no data
+                continue;
+            }
+
+            final ServerLevel world = region.regioniser.world;
+            final ChunkPos chunkCenter = region.getCenterChunk();
+            if (chunkCenter == null) {
+                // region does not exist anymore
+                continue;
+            }
+            final int centerBlockX = ((chunkCenter.x << 4) | 7);
+            final int centerBlockZ = ((chunkCenter.z << 4) | 7);
+            final double util = report.utilisation();
+            final double tps = report.tpsData().segmentAll().average();
+            final double mspt = report.timePerTickData().segmentAll().average() / 1.0E6;
+
+            final int yLoc = 80;
+            final String location = "[w:'" + world.getWorld().getName() + "'," + centerBlockX + "," + yLoc + "," + centerBlockZ + "]";
+            final Component line = Component.text()
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Region around block ", PRIMARY))
+                .append(Component.text(location, INFORMATION))
+                .append(Component.text(":\n", PRIMARY))
+
+                .append(Component.text("    ", PRIMARY))
+                .append(Component.text(ONE_DECIMAL_PLACES.get().format(util * 100.0), CommandUtil.getUtilisationColourRegion(util)))
+                .append(Component.text("% util at ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.get().format(mspt), CommandUtil.getColourForMSPT(mspt)))
+                .append(Component.text(" MSPT at ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.get().format(tps), CommandUtil.getColourForTPS(tps)))
+                .append(Component.text(" TPS\n", PRIMARY))
+
+                .append(Component.text("    ", PRIMARY))
+                .append(formatRegionStats(region.getData().getRegionStats(), (i + 1) != len))
+                .build()
+
+                .clickEvent(ClickEvent.clickEvent(ClickEvent.Action.RUN_COMMAND, "/minecraft:execute as @s in " + world.getWorld().getKey().toString() + " run tp " + centerBlockX + ".5 " + yLoc + " " + centerBlockZ + ".5"))
+                .hoverEvent(HoverEvent.hoverEvent(HoverEvent.Action.SHOW_TEXT, Component.text("Click to teleport to " + location, SECONDARY)));
+
+            lowestRegionsBuilder.append(line);
+        }
+
+        sender.sendMessage(
+            Component.text()
+                .append(Component.text("Server Health Report\n", HEADER, TextDecoration.BOLD))
+
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Online Players: ", PRIMARY))
+                .append(Component.text(Bukkit.getOnlinePlayers().size() + "\n", INFORMATION))
+
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Total regions: ", PRIMARY))
+                .append(Component.text(regions.size() + "\n", INFORMATION))
+
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Utilisation: ", PRIMARY))
+                .append(Component.text(ONE_DECIMAL_PLACES.get().format(totalUtil * 100.0), CommandUtil.getUtilisationColourRegion(totalUtil / (double)maxThreadCount)))
+                .append(Component.text("% / ", PRIMARY))
+                .append(Component.text(ONE_DECIMAL_PLACES.get().format(maxThreadCount * 100.0), INFORMATION))
+                .append(Component.text("%\n", PRIMARY))
+
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Lowest Region TPS: ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.get().format(minTps) + "\n", CommandUtil.getColourForTPS(minTps)))
+
+
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Median Region TPS: ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.get().format(medianTps) + "\n", CommandUtil.getColourForTPS(medianTps)))
+
+                .append(Component.text(" - ", LIST, TextDecoration.BOLD))
+                .append(Component.text("Highest Region TPS: ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.get().format(maxTps) + "\n", CommandUtil.getColourForTPS(maxTps)))
+
+                .append(Component.text("Highest ", HEADER, TextDecoration.BOLD))
+                .append(Component.text(Integer.toString(lowestRegionsCount), INFORMATION, TextDecoration.BOLD))
+                .append(Component.text(" utilisation regions\n", HEADER, TextDecoration.BOLD))
+
+                .append(lowestRegionsBuilder.build())
+                .build()
+        );
+
+        return true;
+    }
+
+    @Override
+    public boolean execute(final CommandSender sender, final String commandLabel, final String[] args) {
+        final String type;
+        if (args.length < 1) {
+            type = "server";
+        } else {
+            type = args[0];
+        }
+
+        switch (type.toLowerCase(Locale.ROOT)) {
+            case "server": {
+                return executeServer(sender, commandLabel, args);
+            }
+            case "region": {
+                if (!(sender instanceof Entity)) {
+                    sender.sendMessage(Component.text("Cannot see current region information as console", NamedTextColor.RED));
+                    return true;
+                }
+                return executeRegion(sender, commandLabel, args);
+            }
+            default: {
+                sender.sendMessage(Component.text("Type '" + args[0] + "' must be one of: [server, region]", NamedTextColor.RED));
+                return true;
+            }
+        }
+    }
+
+    @Override
+    public List<String> tabComplete(final CommandSender sender, final String alias, final String[] args) throws IllegalArgumentException {
+        if (args.length == 0) {
+            if (sender instanceof Entity) {
+                return CommandUtil.getSortedList(Arrays.asList("server", "region"));
+            } else {
+                return CommandUtil.getSortedList(Arrays.asList("server"));
+            }
+        } else if (args.length == 1) {
+            if (sender instanceof Entity) {
+                return CommandUtil.getSortedList(Arrays.asList("server", "region"), args[0]);
+            } else {
+                return CommandUtil.getSortedList(Arrays.asList("server"), args[0]);
+            }
+        }
+        return new ArrayList<>();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/commands/CommandUtil.java b/src/main/java/io/papermc/paper/threadedregions/commands/CommandUtil.java
new file mode 100644
index 0000000000000000000000000000000000000000..d016294fc7eafbddf6d2a758e5803498dfa207b8
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/commands/CommandUtil.java
@@ -0,0 +1,121 @@
+package io.papermc.paper.threadedregions.commands;
+
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.kyori.adventure.text.format.TextColor;
+import net.kyori.adventure.util.HSVLike;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public final class CommandUtil {
+
+    public static List<String> getSortedList(final Iterable<String> iterable) {
+        final List<String> ret = new ArrayList<>();
+        for (final String val : iterable) {
+            ret.add(val);
+        }
+
+        ret.sort(String.CASE_INSENSITIVE_ORDER);
+
+        return ret;
+    }
+
+    public static List<String> getSortedList(final Iterable<String> iterable, final String prefix) {
+        final List<String> ret = new ArrayList<>();
+        for (final String val : iterable) {
+            if (val.regionMatches(0, prefix, 0, prefix.length())) {
+                ret.add(val);
+            }
+        }
+
+        ret.sort(String.CASE_INSENSITIVE_ORDER);
+
+        return ret;
+    }
+
+    public static <T> List<String> getSortedList(final Iterable<T> iterable, final Function<T, String> transform) {
+        final List<String> ret = new ArrayList<>();
+        for (final T val : iterable) {
+            final String transformed = transform.apply(val);
+            if (transformed != null) {
+                ret.add(transformed);
+            }
+        }
+
+        ret.sort(String.CASE_INSENSITIVE_ORDER);
+
+        return ret;
+    }
+
+    public static <T> List<String> getSortedList(final Iterable<T> iterable, final Function<T, String> transform, final String prefix) {
+        final List<String> ret = new ArrayList<>();
+        for (final T val : iterable) {
+            final String string = transform.apply(val);
+            if (string != null && string.regionMatches(0, prefix, 0, prefix.length())) {
+                ret.add(string);
+            }
+        }
+
+        ret.sort(String.CASE_INSENSITIVE_ORDER);
+
+        return ret;
+    }
+
+    public static TextColor getColourForTPS(final double tps) {
+        final double difference = Math.min(Math.abs(20.0 - tps), 20.0);
+        final double coordinate;
+        if (difference <= 2.0) {
+            // >= 18 tps
+            coordinate = 70.0 + ((140.0 - 70.0)/(0.0 - 2.0)) * (difference - 2.0);
+        } else if (difference <= 5.0) {
+            // >= 15 tps
+            coordinate = 30.0 + ((70.0 - 30.0)/(2.0 - 5.0)) * (difference - 5.0);
+        } else if (difference <= 10.0) {
+            // >= 10 tps
+            coordinate = 10.0 + ((30.0 - 10.0)/(5.0 - 10.0)) * (difference - 10.0);
+        } else {
+            // >= 0.0 tps
+            coordinate = 0.0 + ((10.0 - 0.0)/(10.0 - 20.0)) * (difference - 20.0);
+        }
+
+        return TextColor.color(HSVLike.hsvLike((float)(coordinate / 360.0), 85.0f / 100.0f, 80.0f / 100.0f));
+    }
+
+    public static TextColor getColourForMSPT(final double mspt) {
+        final double clamped = Math.min(Math.abs(mspt), 50.0);
+        final double coordinate;
+        if (clamped <= 15.0) {
+            coordinate = 130.0 + ((140.0 - 130.0)/(0.0 - 15.0)) * (clamped - 15.0);
+        } else if (clamped <= 25.0) {
+            coordinate = 90.0 + ((130.0 - 90.0)/(15.0 - 25.0)) * (clamped - 25.0);
+        } else if (clamped <= 35.0) {
+            coordinate = 30.0 + ((90.0 - 30.0)/(25.0 - 35.0)) * (clamped - 35.0);
+        } else if (clamped <= 40.0) {
+            coordinate = 15.0 + ((30.0 - 15.0)/(35.0 - 40.0)) * (clamped - 40.0);
+        } else {
+            coordinate = 0.0 + ((15.0 - 0.0)/(40.0 - 50.0)) * (clamped - 50.0);
+        }
+
+        return TextColor.color(HSVLike.hsvLike((float)(coordinate / 360.0), 85.0f / 100.0f, 80.0f / 100.0f));
+    }
+
+    public static TextColor getUtilisationColourRegion(final double util) {
+        // TODO anything better?
+        // assume 20TPS
+        return getColourForMSPT(util * 50.0);
+    }
+
+    public static ServerPlayer getPlayer(final String name) {
+        for (final ServerPlayer player : MinecraftServer.getServer().getPlayerList().players) {
+            if (player.getGameProfile().getName().equalsIgnoreCase(name)) {
+                return player;
+            }
+        }
+
+        return null;
+    }
+
+    private CommandUtil() {}
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/scheduler/FoliaRegionScheduler.java b/src/main/java/io/papermc/paper/threadedregions/scheduler/FoliaRegionScheduler.java
new file mode 100644
index 0000000000000000000000000000000000000000..a12705793a63b289da13ebabeaf441637c4fe2ed
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/scheduler/FoliaRegionScheduler.java
@@ -0,0 +1,424 @@
+package io.papermc.paper.threadedregions.scheduler;
+
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import ca.spottedleaf.concurrentutil.util.Validate;
+import io.papermc.paper.chunk.system.scheduling.ChunkHolderManager;
+import io.papermc.paper.threadedregions.RegionizedData;
+import io.papermc.paper.threadedregions.RegionizedServer;
+import io.papermc.paper.threadedregions.TickRegionScheduler;
+import io.papermc.paper.util.CoordinateUtils;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.TicketType;
+import net.minecraft.util.Unit;
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.plugin.IllegalPluginAccessException;
+import org.bukkit.plugin.Plugin;
+import java.lang.invoke.VarHandle;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.logging.Level;
+
+public final class FoliaRegionScheduler implements RegionScheduler {
+
+    private static Runnable wrap(final Plugin plugin, final World world, final int chunkX, final int chunkZ, final Runnable run) {
+        return () -> {
+            try {
+                run.run();
+            } catch (final Throwable throwable) {
+                plugin.getLogger().log(Level.WARNING, "Location task for " + plugin.getDescription().getFullName()
+                    + " in world " + world + " at " + chunkX + ", " + chunkZ + " generated an exception", throwable);
+            }
+        };
+    }
+
+    private static final RegionizedData<Scheduler> SCHEDULER_DATA = new RegionizedData<>(null, Scheduler::new, Scheduler.REGIONISER_CALLBACK);
+
+    private static void scheduleInternalOnRegion(final LocationScheduledTask task, final long delay) {
+        SCHEDULER_DATA.get().queueTask(task, delay);
+    }
+
+    private static void scheduleInternalOffRegion(final LocationScheduledTask task, final long delay) {
+        final World world = task.world;
+        if (world == null) {
+            // cancelled
+            return;
+        }
+
+        RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+            ((CraftWorld) world).getHandle(), task.chunkX, task.chunkZ, () -> {
+                scheduleInternalOnRegion(task, delay);
+            }
+        );
+    }
+
+    @Override
+    public void execute(final Plugin plugin, final World world, final int chunkX, final int chunkZ, final Runnable run) {
+        Validate.notNull(plugin, "Plugin may not be null");
+        Validate.notNull(world, "World may not be null");
+        Validate.notNull(run, "Runnable may not be null");
+
+        RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+            ((CraftWorld) world).getHandle(), chunkX, chunkZ, wrap(plugin, world, chunkX, chunkZ, run)
+        );
+    }
+
+    @Override
+    public ScheduledTask run(final Plugin plugin, final World world, final int chunkX, final int chunkZ, final Consumer<ScheduledTask> task) {
+        return this.runDelayed(plugin, world, chunkX, chunkZ, task, 1);
+    }
+
+    @Override
+    public ScheduledTask runDelayed(final Plugin plugin, final World world, final int chunkX, final int chunkZ,
+                                    final Consumer<ScheduledTask> task, final long delayTicks) {
+        Validate.notNull(plugin, "Plugin may not be null");
+        Validate.notNull(world, "World may not be null");
+        Validate.notNull(task, "Task may not be null");
+        if (delayTicks <= 0) {
+            throw new IllegalArgumentException("Delay ticks may not be <= 0");
+        }
+
+        if (!plugin.isEnabled()) {
+            throw new IllegalPluginAccessException("Plugin attempted to register task while disabled");
+        }
+
+        final LocationScheduledTask ret = new LocationScheduledTask(plugin, world, chunkX, chunkZ, -1, task);
+
+        if (Bukkit.isOwnedByCurrentRegion(world, chunkX, chunkZ)) {
+            scheduleInternalOnRegion(ret, delayTicks);
+        } else {
+            scheduleInternalOffRegion(ret, delayTicks);
+        }
+
+        if (!plugin.isEnabled()) {
+            // handle race condition where plugin is disabled asynchronously
+            ret.cancel();
+        }
+
+        return ret;
+    }
+
+    @Override
+    public ScheduledTask runAtFixedRate(final Plugin plugin, final World world, final int chunkX, final int chunkZ,
+                                        final Consumer<ScheduledTask> task, final long initialDelayTicks, final long periodTicks) {
+        Validate.notNull(plugin, "Plugin may not be null");
+        Validate.notNull(world, "World may not be null");
+        Validate.notNull(task, "Task may not be null");
+        if (initialDelayTicks <= 0) {
+            throw new IllegalArgumentException("Initial delay ticks may not be <= 0");
+        }
+        if (periodTicks <= 0) {
+            throw new IllegalArgumentException("Period ticks may not be <= 0");
+        }
+
+        if (!plugin.isEnabled()) {
+            throw new IllegalPluginAccessException("Plugin attempted to register task while disabled");
+        }
+
+        final LocationScheduledTask ret = new LocationScheduledTask(plugin, world, chunkX, chunkZ, periodTicks, task);
+
+        if (Bukkit.isOwnedByCurrentRegion(world, chunkX, chunkZ)) {
+            scheduleInternalOnRegion(ret, initialDelayTicks);
+        } else {
+            scheduleInternalOffRegion(ret, initialDelayTicks);
+        }
+
+        if (!plugin.isEnabled()) {
+            // handle race condition where plugin is disabled asynchronously
+            ret.cancel();
+        }
+
+        return ret;
+    }
+
+    public void tick() {
+        SCHEDULER_DATA.get().tick();
+    }
+
+    private static final class Scheduler {
+        private static final RegionizedData.RegioniserCallback<Scheduler> REGIONISER_CALLBACK = new RegionizedData.RegioniserCallback<>() {
+            @Override
+            public void merge(final Scheduler from, final Scheduler into, final long fromTickOffset) {
+                for (final Iterator<Long2ObjectMap.Entry<Long2ObjectOpenHashMap<List<LocationScheduledTask>>>> sectionIterator = from.tasksByDeadlineBySection.long2ObjectEntrySet().fastIterator();
+                     sectionIterator.hasNext();) {
+                    final Long2ObjectMap.Entry<Long2ObjectOpenHashMap<List<LocationScheduledTask>>> entry = sectionIterator.next();
+                    final long sectionKey = entry.getLongKey();
+                    final Long2ObjectOpenHashMap<List<LocationScheduledTask>> section = entry.getValue();
+
+                    final Long2ObjectOpenHashMap<List<LocationScheduledTask>> sectionAdjusted = new Long2ObjectOpenHashMap<>(section.size());
+
+                    for (final Iterator<Long2ObjectMap.Entry<List<LocationScheduledTask>>> iterator = section.long2ObjectEntrySet().fastIterator();
+                         iterator.hasNext();) {
+                        final Long2ObjectMap.Entry<List<LocationScheduledTask>> e = iterator.next();
+                        final long newTick = e.getLongKey() + fromTickOffset;
+                        final List<LocationScheduledTask> tasks = e.getValue();
+
+                        sectionAdjusted.put(newTick, tasks);
+                    }
+
+                    into.tasksByDeadlineBySection.put(sectionKey, sectionAdjusted);
+                }
+            }
+
+            @Override
+            public void split(final Scheduler from, final int chunkToRegionShift, final Long2ReferenceOpenHashMap<Scheduler> regionToData,
+                              final ReferenceOpenHashSet<Scheduler> dataSet) {
+                for (final Scheduler into : dataSet) {
+                    into.tickCount = from.tickCount;
+                }
+
+                for (final Iterator<Long2ObjectMap.Entry<Long2ObjectOpenHashMap<List<LocationScheduledTask>>>> sectionIterator = from.tasksByDeadlineBySection.long2ObjectEntrySet().fastIterator();
+                     sectionIterator.hasNext();) {
+                    final Long2ObjectMap.Entry<Long2ObjectOpenHashMap<List<LocationScheduledTask>>> entry = sectionIterator.next();
+                    final long sectionKey = entry.getLongKey();
+                    final Long2ObjectOpenHashMap<List<LocationScheduledTask>> section = entry.getValue();
+
+                    final Scheduler into = regionToData.get(sectionKey);
+
+                    into.tasksByDeadlineBySection.put(sectionKey, section);
+                }
+            }
+        };
+
+        private long tickCount = 0L;
+        // map of region section -> map of deadline -> list of tasks
+        private final Long2ObjectOpenHashMap<Long2ObjectOpenHashMap<List<LocationScheduledTask>>> tasksByDeadlineBySection = new Long2ObjectOpenHashMap<>();
+
+        private void addTicket(final int sectionX, final int sectionZ) {
+            final ServerLevel world = TickRegionScheduler.getCurrentRegionizedWorldData().world;
+            final int shift = world.getRegionChunkShift();
+            final int chunkX = sectionX << shift;
+            final int chunkZ = sectionZ << shift;
+
+            world.chunkTaskScheduler.chunkHolderManager.addTicketAtLevel(
+                TicketType.REGION_SCHEDULER_API_HOLD, chunkX, chunkZ, ChunkHolderManager.MAX_TICKET_LEVEL, Unit.INSTANCE
+            );
+        }
+
+        private void removeTicket(final long sectionKey) {
+            final ServerLevel world = TickRegionScheduler.getCurrentRegionizedWorldData().world;
+            final int shift = world.getRegionChunkShift();
+            final int chunkX = CoordinateUtils.getChunkX(sectionKey) << shift;
+            final int chunkZ = CoordinateUtils.getChunkZ(sectionKey) << shift;
+
+            world.chunkTaskScheduler.chunkHolderManager.removeTicketAtLevel(
+                TicketType.REGION_SCHEDULER_API_HOLD, chunkX, chunkZ, ChunkHolderManager.MAX_TICKET_LEVEL, Unit.INSTANCE
+            );
+        }
+
+        private void queueTask(final LocationScheduledTask task, final long delay) {
+            // note: must be on the thread that owns this scheduler
+            // note: delay > 0
+
+            final World world = task.world;
+            if (world == null) {
+                // cancelled
+                return;
+            }
+
+            final int shift = ((CraftWorld)world).getHandle().getRegionChunkShift();
+            final int sectionX = task.chunkX >> shift;
+            final int sectionZ = task.chunkZ >> shift;
+
+            final Long2ObjectOpenHashMap<List<LocationScheduledTask>> section =
+                this.tasksByDeadlineBySection.computeIfAbsent(CoordinateUtils.getChunkKey(sectionX, sectionZ), (final long keyInMap) -> {
+                    return new Long2ObjectOpenHashMap<>();
+                }
+            );
+
+            if (section.isEmpty()) {
+                // need to keep the scheduler loaded for this location in order for tick() to be called...
+                this.addTicket(sectionX, sectionZ);
+            }
+
+            section.computeIfAbsent(this.tickCount + delay, (final long keyInMap) -> {
+                return new ArrayList<>();
+            }).add(task);
+        }
+
+        public void tick() {
+            ++this.tickCount;
+
+            final List<LocationScheduledTask> run = new ArrayList<>();
+
+            for (final Iterator<Long2ObjectMap.Entry<Long2ObjectOpenHashMap<List<LocationScheduledTask>>>> sectionIterator = this.tasksByDeadlineBySection.long2ObjectEntrySet().fastIterator();
+                 sectionIterator.hasNext();) {
+                final Long2ObjectMap.Entry<Long2ObjectOpenHashMap<List<LocationScheduledTask>>> entry = sectionIterator.next();
+                final long sectionKey = entry.getLongKey();
+                final Long2ObjectOpenHashMap<List<LocationScheduledTask>> section = entry.getValue();
+
+                final List<LocationScheduledTask> tasks = section.remove(this.tickCount);
+
+                if (tasks == null) {
+                    continue;
+                }
+
+                run.addAll(tasks);
+
+                if (section.isEmpty()) {
+                    this.removeTicket(sectionKey);
+                    sectionIterator.remove();
+                }
+            }
+
+            for (int i = 0, len = run.size(); i < len; ++i) {
+                run.get(i).run();
+            }
+        }
+    }
+
+    private static final class LocationScheduledTask implements ScheduledTask, Runnable {
+
+        private static final int STATE_IDLE                = 0;
+        private static final int STATE_EXECUTING           = 1;
+        private static final int STATE_EXECUTING_CANCELLED = 2;
+        private static final int STATE_FINISHED            = 3;
+        private static final int STATE_CANCELLED           = 4;
+
+        private final Plugin plugin;
+        private final int chunkX;
+        private final int chunkZ;
+        private final long repeatDelay; // in ticks
+        private World world;
+        private Consumer<ScheduledTask> run;
+
+        private volatile int state;
+        private static final VarHandle STATE_HANDLE = ConcurrentUtil.getVarHandle(LocationScheduledTask.class, "state", int.class);
+
+        private LocationScheduledTask(final Plugin plugin, final World world, final int chunkX, final int chunkZ,
+                                      final long repeatDelay, final Consumer<ScheduledTask> run) {
+            this.plugin = plugin;
+            this.world = world;
+            this.chunkX = chunkX;
+            this.chunkZ = chunkZ;
+            this.repeatDelay = repeatDelay;
+            this.run = run;
+        }
+
+        private final int getStateVolatile() {
+            return (int)STATE_HANDLE.get(this);
+        }
+
+        private final int compareAndExchangeStateVolatile(final int expect, final int update) {
+            return (int)STATE_HANDLE.compareAndExchange(this, expect, update);
+        }
+
+        private final void setStateVolatile(final int value) {
+            STATE_HANDLE.setVolatile(this, value);
+        }
+
+        @Override
+        public void run() {
+            if (!this.plugin.isEnabled()) {
+                // don't execute if the plugin is disabled
+                return;
+            }
+
+            final boolean repeating = this.isRepeatingTask();
+            if (STATE_IDLE != this.compareAndExchangeStateVolatile(STATE_IDLE, STATE_EXECUTING)) {
+                // cancelled
+                return;
+            }
+
+            try {
+                this.run.accept(this);
+            } catch (final Throwable throwable) {
+                this.plugin.getLogger().log(Level.WARNING, "Location task for " + this.plugin.getDescription().getFullName()
+                    + " in world " + world + " at " + chunkX + ", " + chunkZ + " generated an exception", throwable);
+            } finally {
+                boolean reschedule = false;
+                 if (!repeating) {
+                    this.setStateVolatile(STATE_FINISHED);
+                } else if (!this.plugin.isEnabled()) {
+                     this.setStateVolatile(STATE_CANCELLED);
+                } else if (STATE_EXECUTING == this.compareAndExchangeStateVolatile(STATE_EXECUTING, STATE_IDLE)) {
+                    reschedule = true;
+                } // else: cancelled repeating task
+
+                if (!reschedule) {
+                    this.run = null;
+                    this.world = null;
+                } else {
+                    FoliaRegionScheduler.scheduleInternalOnRegion(this, this.repeatDelay);
+                }
+            }
+        }
+
+        @Override
+        public Plugin getOwningPlugin() {
+            return this.plugin;
+        }
+
+        @Override
+        public boolean isRepeatingTask() {
+            return this.repeatDelay > 0;
+        }
+
+        @Override
+        public CancelledState cancel() {
+            for (int curr = this.getStateVolatile();;) {
+                switch (curr) {
+                    case STATE_IDLE: {
+                        if (STATE_IDLE == (curr = this.compareAndExchangeStateVolatile(STATE_IDLE, STATE_CANCELLED))) {
+                            this.state = STATE_CANCELLED;
+                            this.run = null;
+                            this.world = null;
+                            return CancelledState.CANCELLED_BY_CALLER;
+                        }
+                        // try again
+                        continue;
+                    }
+                    case STATE_EXECUTING: {
+                        if (!this.isRepeatingTask()) {
+                            return CancelledState.RUNNING;
+                        }
+                        if (STATE_EXECUTING == (curr = this.compareAndExchangeStateVolatile(STATE_EXECUTING, STATE_EXECUTING_CANCELLED))) {
+                            return CancelledState.NEXT_RUNS_CANCELLED;
+                        }
+                        // try again
+                        continue;
+                    }
+                    case STATE_EXECUTING_CANCELLED: {
+                        return CancelledState.NEXT_RUNS_CANCELLED_ALREADY;
+                    }
+                    case STATE_FINISHED: {
+                        return CancelledState.ALREADY_EXECUTED;
+                    }
+                    case STATE_CANCELLED: {
+                        return CancelledState.CANCELLED_ALREADY;
+                    }
+                    default: {
+                        throw new IllegalStateException("Unknown state: " + curr);
+                    }
+                }
+            }
+        }
+
+        @Override
+        public ExecutionState getExecutionState() {
+            final int state = this.getStateVolatile();
+            switch (state) {
+                case STATE_IDLE:
+                    return ExecutionState.IDLE;
+                case STATE_EXECUTING:
+                    return ExecutionState.RUNNING;
+                case STATE_EXECUTING_CANCELLED:
+                    return ExecutionState.CANCELLED_RUNNING;
+                case STATE_FINISHED:
+                    return ExecutionState.FINISHED;
+                case STATE_CANCELLED:
+                    return ExecutionState.CANCELLED;
+                default: {
+                    throw new IllegalStateException("Unknown state: " + state);
+                }
+            }
+        }
+    }
+}
diff --git a/src/main/java/io/papermc/paper/util/CachedLists.java b/src/main/java/io/papermc/paper/util/CachedLists.java
index e08f4e39db4ee3fed62e37364d17dcc5c5683504..7e92e14cdb9f3d895550991b2ea154a60f9c091b 100644
--- a/src/main/java/io/papermc/paper/util/CachedLists.java
+++ b/src/main/java/io/papermc/paper/util/CachedLists.java
@@ -9,49 +9,57 @@ import java.util.List;
 public final class CachedLists {
 
     // Paper start - optimise collisions
-    static final UnsafeList<AABB> TEMP_COLLISION_LIST = new UnsafeList<>(1024);
-    static boolean tempCollisionListInUse;
+    // Folia - region threading
 
     public static UnsafeList<AABB> getTempCollisionList() {
-        if (!Bukkit.isPrimaryThread() || tempCollisionListInUse) {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        if (worldData == null) {
             return new UnsafeList<>(16);
         }
-        tempCollisionListInUse = true;
-        return TEMP_COLLISION_LIST;
+        return worldData.tempCollisionList.get();
+        // Folia end - region threading
     }
 
     public static void returnTempCollisionList(List<AABB> list) {
-        if (list != TEMP_COLLISION_LIST) {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        if (worldData == null) {
             return;
         }
-        ((UnsafeList)list).setSize(0);
-        tempCollisionListInUse = false;
+        worldData.tempCollisionList.ret(list);
+        // Folia end - region threading
     }
 
-    static final UnsafeList<Entity> TEMP_GET_ENTITIES_LIST = new UnsafeList<>(1024);
-    static boolean tempGetEntitiesListInUse;
+    // Folia - region threading
 
     public static UnsafeList<Entity> getTempGetEntitiesList() {
-        if (!Bukkit.isPrimaryThread() || tempGetEntitiesListInUse) {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        if (worldData == null) {
             return new UnsafeList<>(16);
         }
-        tempGetEntitiesListInUse = true;
-        return TEMP_GET_ENTITIES_LIST;
+        return worldData.tempEntitiesList.get();
+        // Folia end - region threading
     }
 
     public static void returnTempGetEntitiesList(List<Entity> list) {
-        if (list != TEMP_GET_ENTITIES_LIST) {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        if (worldData == null) {
             return;
         }
-        ((UnsafeList)list).setSize(0);
-        tempGetEntitiesListInUse = false;
+        worldData.tempEntitiesList.ret(list);
+        // Folia end - region threading
     }
     // Paper end - optimise collisions
 
     public static void reset() {
-        // Paper start - optimise collisions
-        TEMP_COLLISION_LIST.completeReset();
-        TEMP_GET_ENTITIES_LIST.completeReset();
-        // Paper end - optimise collisions
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        if (worldData != null) {
+            worldData.resetCollisionLists();
+        }
+        // Folia end - region threading
     }
 }
diff --git a/src/main/java/io/papermc/paper/util/CollisionUtil.java b/src/main/java/io/papermc/paper/util/CollisionUtil.java
index ee0331a6bc40cdde08d926fd8eb1dc642630c2e5..feea642338c7fdd96d9c4d2ea5564f1c3743195c 100644
--- a/src/main/java/io/papermc/paper/util/CollisionUtil.java
+++ b/src/main/java/io/papermc/paper/util/CollisionUtil.java
@@ -1623,7 +1623,7 @@ public final class CollisionUtil {
 
         for (int currChunkZ = minChunkZ; currChunkZ <= maxChunkZ; ++currChunkZ) {
             for (int currChunkX = minChunkX; currChunkX <= maxChunkX; ++currChunkX) {
-                final ChunkAccess chunk = loadChunks ? chunkSource.getChunk(currChunkX, currChunkZ, ChunkStatus.FULL, true) : chunkSource.getChunkAtIfLoadedImmediately(currChunkX, currChunkZ);
+                final ChunkAccess chunk = !io.papermc.paper.util.TickThread.isTickThreadFor(chunkSource.chunkMap.level, currChunkX, currChunkZ) ? null : (loadChunks ? chunkSource.getChunk(currChunkX, currChunkZ, ChunkStatus.FULL, true) : chunkSource.getChunkAtIfLoadedImmediately(currChunkX, currChunkZ)); // Folia - ignore chunk if we do not own the region
 
                 if (chunk == null) {
                     if ((collisionFlags & COLLISION_FLAG_COLLIDE_WITH_UNLOADED_CHUNKS) != 0) {
diff --git a/src/main/java/io/papermc/paper/util/CoordinateUtils.java b/src/main/java/io/papermc/paper/util/CoordinateUtils.java
index 413e4b6da027876dbbe8eb78f2568a440f431547..3a7dbcb9964723b8ed5e6b0a1ee4267923c746e4 100644
--- a/src/main/java/io/papermc/paper/util/CoordinateUtils.java
+++ b/src/main/java/io/papermc/paper/util/CoordinateUtils.java
@@ -5,6 +5,7 @@ import net.minecraft.core.SectionPos;
 import net.minecraft.util.Mth;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.phys.Vec3;
 
 public final class CoordinateUtils {
 
@@ -122,6 +123,31 @@ public final class CoordinateUtils {
         return ((long)entity.getX() & 0x7FFFFFF) | (((long)entity.getZ() & 0x7FFFFFF) << 27) | ((long)entity.getY() << 54);
     }
 
+    // TODO rebase
+    public static int getBlockX(final Vec3 pos) {
+        return Mth.floor(pos.x);
+    }
+
+    public static int getBlockY(final Vec3 pos) {
+        return Mth.floor(pos.y);
+    }
+
+    public static int getBlockZ(final Vec3 pos) {
+        return Mth.floor(pos.z);
+    }
+
+    public static int getChunkX(final Vec3 pos) {
+        return Mth.floor(pos.x) >> 4;
+    }
+
+    public static int getChunkY(final Vec3 pos) {
+        return Mth.floor(pos.y) >> 4;
+    }
+
+    public static int getChunkZ(final Vec3 pos) {
+        return Mth.floor(pos.z) >> 4;
+    }
+
     private CoordinateUtils() {
         throw new RuntimeException();
     }
diff --git a/src/main/java/io/papermc/paper/util/MCUtil.java b/src/main/java/io/papermc/paper/util/MCUtil.java
index e028353e0261310afc42ca0454b723d9f1ffc131..08d282400644be5949f28eb879b333cc221da2cc 100644
--- a/src/main/java/io/papermc/paper/util/MCUtil.java
+++ b/src/main/java/io/papermc/paper/util/MCUtil.java
@@ -337,6 +337,7 @@ public final class MCUtil {
      */
     public static void ensureMain(String reason, Runnable run) {
         if (!isMainThread()) {
+            if (true) throw new UnsupportedOperationException(); // Folia - region threading
             if (reason != null) {
                 MinecraftServer.LOGGER.warn("Asynchronous " + reason + "!", new IllegalStateException());
             }
@@ -477,6 +478,30 @@ public final class MCUtil {
         return new Location(world.getWorld(), pos.getX(), pos.getY(), pos.getZ());
     }
 
+    // Folia start - TODO MERGE INTO MCUTIL
+    /**
+     * Converts a NMS World/Vector to Bukkit Location
+     * @param world
+     * @param pos
+     * @return
+     */
+    public static Location toLocation(Level world, Vec3 pos) {
+        return new Location(world.getWorld(), pos.x(), pos.y(), pos.z());
+    }
+
+    /**
+     * Converts a NMS World/Vector to Bukkit Location
+     * @param world
+     * @param pos
+     * @param yaw
+     * @param pitch
+     * @return
+     */
+    public static Location toLocation(Level world, Vec3 pos, float yaw, float pitch) {
+        return new Location(world.getWorld(), pos.x(), pos.y(), pos.z(), yaw, pitch);
+    }
+    // Folia end - TODO MERGE INTO MCUTIL
+
     /**
      * Converts an NMS entity's current location to a Bukkit Location
      * @param entity
diff --git a/src/main/java/io/papermc/paper/util/TickThread.java b/src/main/java/io/papermc/paper/util/TickThread.java
index bdaf062f9b66ceab303a0807eca301342886a8ea..906f1c9e619a924c622acc76652a4569305edc8d 100644
--- a/src/main/java/io/papermc/paper/util/TickThread.java
+++ b/src/main/java/io/papermc/paper/util/TickThread.java
@@ -1,5 +1,11 @@
 package io.papermc.paper.util;
 
+import io.papermc.paper.threadedregions.RegionShutdownThread;
+import io.papermc.paper.threadedregions.RegionizedServer;
+import io.papermc.paper.threadedregions.RegionizedWorldData;
+import io.papermc.paper.threadedregions.ThreadedRegionizer;
+import io.papermc.paper.threadedregions.TickRegionScheduler;
+import io.papermc.paper.threadedregions.TickRegions;
 import net.minecraft.core.BlockPos;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.level.ServerLevel;
@@ -114,46 +120,149 @@ public class TickThread extends Thread {
     }
 
     public static boolean isShutdownThread() {
-        return false;
+        return Thread.currentThread().getClass() == RegionShutdownThread.class;
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final BlockPos pos) {
-        return isTickThread();
+        return isTickThreadFor(world, pos.getX() >> 4, pos.getZ() >> 4);
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final ChunkPos pos) {
-        return isTickThread();
+        return isTickThreadFor(world, pos.x, pos.z);
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final Vec3 pos) {
-        return isTickThread();
+        return isTickThreadFor(world, Mth.floor(pos.x) >> 4, Mth.floor(pos.z) >> 4);
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final int chunkX, final int chunkZ) {
-        return isTickThread();
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            return isShutdownThread();
+        }
+        return world.regioniser.getRegionAtUnsynchronised(chunkX, chunkZ) == region;
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final AABB aabb) {
-        return isTickThread();
+        return isTickThreadFor(
+            world,
+            CoordinateUtils.getChunkCoordinate(aabb.minX), CoordinateUtils.getChunkCoordinate(aabb.minZ),
+            CoordinateUtils.getChunkCoordinate(aabb.maxX), CoordinateUtils.getChunkCoordinate(aabb.maxZ)
+        );
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final double blockX, final double blockZ) {
-        return isTickThread();
+        return isTickThreadFor(world, CoordinateUtils.getChunkCoordinate(blockX), CoordinateUtils.getChunkCoordinate(blockZ));
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final Vec3 position, final Vec3 deltaMovement, final int buffer) {
-        return isTickThread();
+        final int fromChunkX = CoordinateUtils.getChunkX(position);
+        final int fromChunkZ = CoordinateUtils.getChunkZ(position);
+
+        final int toChunkX = CoordinateUtils.getChunkCoordinate(position.x + deltaMovement.x);
+        final int toChunkZ = CoordinateUtils.getChunkCoordinate(position.z + deltaMovement.z);
+
+        // expect from < to, but that may not be the case
+        return isTickThreadFor(
+            world,
+            Math.min(fromChunkX, toChunkX) - buffer,
+            Math.min(fromChunkZ, toChunkZ) - buffer,
+            Math.max(fromChunkX, toChunkX) + buffer,
+            Math.max(fromChunkZ, toChunkZ) + buffer
+        );
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final int fromChunkX, final int fromChunkZ, final int toChunkX, final int toChunkZ) {
-        return isTickThread();
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            return isShutdownThread();
+        }
+
+        final int shift = world.regioniser.sectionChunkShift;
+
+        final int minSectionX = fromChunkX >> shift;
+        final int maxSectionX = toChunkX >> shift;
+        final int minSectionZ = fromChunkZ >> shift;
+        final int maxSectionZ = toChunkZ >> shift;
+
+        for (int secZ = minSectionZ; secZ <= maxSectionZ; ++secZ) {
+            for (int secX = minSectionX; secX <= maxSectionX; ++secX) {
+                final int lowerLeftCX = secX << shift;
+                final int lowerLeftCZ = secZ << shift;
+                if (world.regioniser.getRegionAtUnsynchronised(lowerLeftCX, lowerLeftCZ) != region) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
     }
 
     public static boolean isTickThreadFor(final ServerLevel world, final int chunkX, final int chunkZ, final int radius) {
-        return isTickThread();
+        return isTickThreadFor(world, chunkX - radius, chunkZ - radius, chunkX + radius, chunkZ + radius);
     }
 
     public static boolean isTickThreadFor(final Entity entity) {
-        return isTickThread();
+        if (entity == null) {
+            return true;
+        }
+        final ThreadedRegionizer.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            if (RegionizedServer.isGlobalTickThread()) {
+                if (entity instanceof ServerPlayer serverPlayer) {
+                    final ServerGamePacketListenerImpl possibleBad = serverPlayer.connection;
+                    if (possibleBad == null) {
+                        return true;
+                    }
+
+                    final net.minecraft.network.PacketListener packetListener = possibleBad.connection.getPacketListener();
+                    if (packetListener instanceof ServerGamePacketListenerImpl gamePacketListener) {
+                        return gamePacketListener.waitingForSwitchToConfig;
+                    }
+                    if (packetListener instanceof net.minecraft.server.network.ServerConfigurationPacketListenerImpl configurationPacketListener) {
+                        return !configurationPacketListener.switchToMain;
+                    }
+                    return true;
+                } else {
+                    return false;
+                }
+            }
+            if (isShutdownThread()) {
+                return true;
+            }
+            if (entity instanceof ServerPlayer serverPlayer) {
+                // off-main access to server player is never ok, server player is owned by one of global context or region context always
+                return false;
+            }
+            // only own entities that have not yet been added to the world
+
+            // if the entity is removed, then it was in the world previously - which means that a region containing its location
+            // owns it
+            // if the entity has a callback, then it is contained in a world
+            return entity.hasNullCallback() && !entity.isRemoved();
+        }
+
+        final Level level = entity.level();
+        if (level != region.regioniser.world) {
+            // world mismatch
+            return false;
+        }
+
+        final RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+
+        // pass through the check if the entity is removed and we own its chunk
+        if (worldData.hasEntity(entity)) {
+            return true;
+        }
+        
+        if (entity instanceof ServerPlayer serverPlayer) {
+            ServerGamePacketListenerImpl conn = serverPlayer.connection;
+            return conn != null && worldData.connections.contains(conn.connection);
+        } else {
+            return ((entity.hasNullCallback() || entity.isRemoved())) && isTickThreadFor((ServerLevel)level, entity.chunkPosition());
+        }
     }
 }
diff --git a/src/main/java/io/papermc/paper/util/set/LinkedSortedSet.java b/src/main/java/io/papermc/paper/util/set/LinkedSortedSet.java
new file mode 100644
index 0000000000000000000000000000000000000000..cf9b66afc1762dbe2c625f09f9e804ca7dc0f128
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/set/LinkedSortedSet.java
@@ -0,0 +1,273 @@
+package io.papermc.paper.util.set;
+
+import java.util.Comparator;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+// TODO rebase into util patch
+public final class LinkedSortedSet<E> implements Iterable<E> {
+
+    public final Comparator<? super E> comparator;
+
+    protected Link<E> head;
+    protected Link<E> tail;
+
+    public LinkedSortedSet() {
+        this((Comparator)Comparator.naturalOrder());
+    }
+
+    public LinkedSortedSet(final Comparator<? super E> comparator) {
+        this.comparator = comparator;
+    }
+
+    public void clear() {
+        this.head = this.tail = null;
+    }
+
+    public boolean isEmpty() {
+        return this.head == null;
+    }
+
+    public E first() {
+        final Link<E> head = this.head;
+        return head == null ? null : head.element;
+    }
+
+    public E last() {
+        final Link<E> tail = this.tail;
+        return tail == null ? null : tail.element;
+    }
+
+    public boolean containsFirst(final E element) {
+        final Comparator<? super E> comparator = this.comparator;
+        for (Link<E> curr = this.head; curr != null; curr = curr.next) {
+            if (comparator.compare(element, curr.element) == 0) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public boolean containsLast(final E element) {
+        final Comparator<? super E> comparator = this.comparator;
+        for (Link<E> curr = this.tail; curr != null; curr = curr.prev) {
+            if (comparator.compare(element, curr.element) == 0) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private void removeNode(final Link<E> node) {
+        final Link<E> prev = node.prev;
+        final Link<E> next = node.next;
+
+        // help GC
+        node.element = null;
+        node.prev = null;
+        node.next = null;
+
+        if (prev == null) {
+            this.head = next;
+        } else {
+            prev.next = next;
+        }
+
+        if (next == null) {
+            this.tail = prev;
+        } else {
+            next.prev = prev;
+        }
+    }
+
+    public boolean remove(final Link<E> link) {
+        if (link.element == null) {
+            return false;
+        }
+
+        this.removeNode(link);
+        return true;
+    }
+
+    public boolean removeFirst(final E element) {
+        final Comparator<? super E> comparator = this.comparator;
+        for (Link<E> curr = this.head; curr != null; curr = curr.next) {
+            if (comparator.compare(element, curr.element) == 0) {
+                this.removeNode(curr);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public boolean removeLast(final E element) {
+        final Comparator<? super E> comparator = this.comparator;
+        for (Link<E> curr = this.tail; curr != null; curr = curr.prev) {
+            if (comparator.compare(element, curr.element) == 0) {
+                this.removeNode(curr);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public Iterator<E> iterator() {
+        return new Iterator<>() {
+            private Link<E> next = LinkedSortedSet.this.head;
+
+            @Override
+            public boolean hasNext() {
+                return this.next != null;
+            }
+
+            @Override
+            public E next() {
+                final Link<E> next = this.next;
+                if (next == null) {
+                    throw new NoSuchElementException();
+                }
+                this.next = next.next;
+                return next.element;
+            }
+        };
+    }
+
+    public E pollFirst() {
+        final Link<E> head = this.head;
+        if (head == null) {
+            return null;
+        }
+
+        final E ret = head.element;
+        final Link<E> next = head.next;
+
+        // unlink head
+        this.head = next;
+        if (next == null) {
+            this.tail = null;
+        } else {
+            next.prev = null;
+        }
+
+        // help GC
+        head.element = null;
+        head.next = null;
+
+        return ret;
+    }
+
+    public E pollLast() {
+        final Link<E> tail = this.tail;
+        if (tail == null) {
+            return null;
+        }
+
+        final E ret = tail.element;
+        final Link<E> prev = tail.prev;
+
+        // unlink tail
+        this.tail = prev;
+        if (prev == null) {
+            this.head = null;
+        } else {
+            prev.next = null;
+        }
+
+        // help GC
+        tail.element = null;
+        tail.prev = null;
+
+        return ret;
+    }
+
+    public Link<E> addLast(final E element) {
+        final Comparator<? super E> comparator = this.comparator;
+
+        Link<E> curr = this.tail;
+        if (curr != null) {
+            int compare;
+
+            while ((compare = comparator.compare(element, curr.element)) < 0) {
+                Link<E> prev = curr;
+                curr = curr.prev;
+                if (curr != null) {
+                    continue;
+                }
+                return this.head = prev.prev = new Link<>(element, null, prev);
+            }
+
+            if (compare != 0) {
+                // insert after curr
+                final Link<E> next = curr.next;
+                final Link<E> insert = new Link<>(element, curr, next);
+                curr.next = insert;
+
+                if (next == null) {
+                    this.tail = insert;
+                } else {
+                    next.prev = insert;
+                }
+                return insert;
+            }
+
+            return null;
+        } else {
+            return this.head = this.tail = new Link<>(element);
+        }
+    }
+
+    public Link<E> addFirst(final E element) {
+        final Comparator<? super E> comparator = this.comparator;
+
+        Link<E> curr = this.head;
+        if (curr != null) {
+            int compare;
+
+            while ((compare = comparator.compare(element, curr.element)) > 0) {
+                Link<E> prev = curr;
+                curr = curr.next;
+                if (curr != null) {
+                    continue;
+                }
+                return this.tail = prev.next = new Link<>(element, prev, null);
+            }
+
+            if (compare != 0) {
+                // insert before curr
+                final Link<E> prev = curr.prev;
+                final Link<E> insert = new Link<>(element, prev, curr);
+                curr.prev = insert;
+
+                if (prev == null) {
+                    this.head = insert;
+                } else {
+                    prev.next = insert;
+                }
+                return insert;
+            }
+
+            return null;
+        } else {
+            return this.head = this.tail = new Link<>(element);
+        }
+    }
+
+    public static final class Link<E> {
+        private E element;
+        private Link<E> prev;
+        private Link<E> next;
+
+        private Link() {}
+
+        private Link(final E element) {
+            this.element = element;
+        }
+
+        private Link(final E element, final Link<E> prev, final Link<E> next) {
+            this.element = element;
+            this.prev = prev;
+            this.next = next;
+        }
+    }
+}
diff --git a/src/main/java/net/minecraft/commands/CommandSourceStack.java b/src/main/java/net/minecraft/commands/CommandSourceStack.java
index f341813e9713e39bfe142ca34b751de3d8efd25b..7793797dfae906e5181dff517a7d04c95e869a37 100644
--- a/src/main/java/net/minecraft/commands/CommandSourceStack.java
+++ b/src/main/java/net/minecraft/commands/CommandSourceStack.java
@@ -68,7 +68,7 @@ public class CommandSourceStack implements ExecutionCommandSource<CommandSourceS
     public boolean bypassSelectorPermissions = false; // Paper - add bypass for selector permissions
 
     public CommandSourceStack(CommandSource output, Vec3 pos, Vec2 rot, ServerLevel world, int level, String name, Component displayName, MinecraftServer server, @Nullable Entity entity) {
-        this(output, pos, rot, world, level, name, displayName, server, entity, false, CommandResultCallback.EMPTY, EntityAnchorArgument.Anchor.FEET, CommandSigningContext.ANONYMOUS, TaskChainer.immediate(server));
+        this(output, pos, rot, world, level, name, displayName, server, entity, false, CommandResultCallback.EMPTY, EntityAnchorArgument.Anchor.FEET, CommandSigningContext.ANONYMOUS, TaskChainer.immediate((Runnable run) -> { io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(run);})); // Folia - region threading
     }
 
     protected CommandSourceStack(CommandSource output, Vec3 pos, Vec2 rot, ServerLevel world, int level, String name, Component displayName, MinecraftServer server, @Nullable Entity entity, boolean silent, CommandResultCallback resultStorer, EntityAnchorArgument.Anchor entityAnchor, CommandSigningContext signedArguments, TaskChainer messageChainTaskQueue) {
diff --git a/src/main/java/net/minecraft/commands/Commands.java b/src/main/java/net/minecraft/commands/Commands.java
index b7f338e982d0dcab99137ab6dc200b82ac6b7cba..4f25b35a037e6c697e5e345f38b94a8e4b436ad7 100644
--- a/src/main/java/net/minecraft/commands/Commands.java
+++ b/src/main/java/net/minecraft/commands/Commands.java
@@ -159,13 +159,13 @@ public class Commands {
         AdvancementCommands.register(this.dispatcher);
         AttributeCommand.register(this.dispatcher, commandRegistryAccess);
         ExecuteCommand.register(this.dispatcher, commandRegistryAccess);
-        BossBarCommands.register(this.dispatcher);
+        //BossBarCommands.register(this.dispatcher); // Folia - region threading - TODO
         ClearInventoryCommands.register(this.dispatcher, commandRegistryAccess);
-        CloneCommands.register(this.dispatcher, commandRegistryAccess);
+        //CloneCommands.register(this.dispatcher, commandRegistryAccess); // Folia - region threading - TODO
         DamageCommand.register(this.dispatcher, commandRegistryAccess);
-        DataCommands.register(this.dispatcher);
-        DataPackCommand.register(this.dispatcher);
-        DebugCommand.register(this.dispatcher);
+        //DataCommands.register(this.dispatcher); // Folia - region threading - TODO
+        //DataPackCommand.register(this.dispatcher); // Folia - region threading - TODO
+        //DebugCommand.register(this.dispatcher); // Folia - region threading - TODO
         DefaultGameModeCommands.register(this.dispatcher);
         DifficultyCommand.register(this.dispatcher);
         EffectCommands.register(this.dispatcher, commandRegistryAccess);
@@ -175,46 +175,46 @@ public class Commands {
         FillCommand.register(this.dispatcher, commandRegistryAccess);
         FillBiomeCommand.register(this.dispatcher, commandRegistryAccess);
         ForceLoadCommand.register(this.dispatcher);
-        FunctionCommand.register(this.dispatcher);
+        //FunctionCommand.register(this.dispatcher); // Folia - region threading - TODO
         GameModeCommand.register(this.dispatcher);
         GameRuleCommand.register(this.dispatcher);
         GiveCommand.register(this.dispatcher, commandRegistryAccess);
         HelpCommand.register(this.dispatcher);
-        ItemCommands.register(this.dispatcher, commandRegistryAccess);
+        //ItemCommands.register(this.dispatcher, commandRegistryAccess); // Folia - region threading - TODO later
         KickCommand.register(this.dispatcher);
         KillCommand.register(this.dispatcher);
         ListPlayersCommand.register(this.dispatcher);
         LocateCommand.register(this.dispatcher, commandRegistryAccess);
-        LootCommand.register(this.dispatcher, commandRegistryAccess);
+        //LootCommand.register(this.dispatcher, commandRegistryAccess); // Folia - region threading - TODO later
         MsgCommand.register(this.dispatcher);
         ParticleCommand.register(this.dispatcher, commandRegistryAccess);
         PlaceCommand.register(this.dispatcher);
         PlaySoundCommand.register(this.dispatcher);
         RandomCommand.register(this.dispatcher);
-        ReloadCommand.register(this.dispatcher);
+        //ReloadCommand.register(this.dispatcher); // Folia - region threading
         RecipeCommand.register(this.dispatcher);
-        ReturnCommand.register(this.dispatcher);
-        RideCommand.register(this.dispatcher);
+        //ReturnCommand.register(this.dispatcher); // Folia - region threading - TODO later
+        //RideCommand.register(this.dispatcher); // Folia - region threading - TODO later
         SayCommand.register(this.dispatcher);
-        ScheduleCommand.register(this.dispatcher);
-        ScoreboardCommand.register(this.dispatcher);
+        //ScheduleCommand.register(this.dispatcher); // Folia - region threading
+        //ScoreboardCommand.register(this.dispatcher); // Folia - region threading - TODO later
         SeedCommand.register(this.dispatcher, environment != Commands.CommandSelection.INTEGRATED);
         SetBlockCommand.register(this.dispatcher, commandRegistryAccess);
         SetSpawnCommand.register(this.dispatcher);
         SetWorldSpawnCommand.register(this.dispatcher);
-        SpectateCommand.register(this.dispatcher);
-        SpreadPlayersCommand.register(this.dispatcher);
+        //SpectateCommand.register(this.dispatcher); // Folia - region threading - TODO later
+        //SpreadPlayersCommand.register(this.dispatcher); // Folia - region threading - TODO later
         StopSoundCommand.register(this.dispatcher);
         SummonCommand.register(this.dispatcher, commandRegistryAccess);
-        TagCommand.register(this.dispatcher);
-        TeamCommand.register(this.dispatcher);
-        TeamMsgCommand.register(this.dispatcher);
+        //TagCommand.register(this.dispatcher); // Folia - region threading - TODO later
+        //TeamCommand.register(this.dispatcher); // Folia - region threading - TODO later
+        //TeamMsgCommand.register(this.dispatcher); // Folia - region threading - TODO later
         TeleportCommand.register(this.dispatcher);
         TellRawCommand.register(this.dispatcher);
-        TickCommand.register(this.dispatcher);
+        //TickCommand.register(this.dispatcher); // Folia - region threading - TODO later
         TimeCommand.register(this.dispatcher);
         TitleCommand.register(this.dispatcher);
-        TriggerCommand.register(this.dispatcher);
+        //TriggerCommand.register(this.dispatcher); // Folia - region threading - TODO later
         WeatherCommand.register(this.dispatcher);
         WorldBorderCommand.register(this.dispatcher);
         if (JvmProfiler.INSTANCE.isAvailable()) {
@@ -243,8 +243,8 @@ public class Commands {
             OpCommand.register(this.dispatcher);
             PardonCommand.register(this.dispatcher);
             PardonIpCommand.register(this.dispatcher);
-            PerfCommand.register(this.dispatcher);
-            SaveAllCommand.register(this.dispatcher);
+            //PerfCommand.register(this.dispatcher); // Folia - region threading - TODO later
+            //SaveAllCommand.register(this.dispatcher); // Folia - region threading - TODO later
             SaveOffCommand.register(this.dispatcher);
             SaveOnCommand.register(this.dispatcher);
             SetPlayerIdleTimeoutCommand.register(this.dispatcher);
@@ -498,9 +498,12 @@ public class Commands {
         }
         // Paper start - Perf: Async command map building
         new com.destroystokyo.paper.event.brigadier.AsyncPlayerSendCommandsEvent<CommandSourceStack>(player.getBukkitEntity(), (RootCommandNode) rootcommandnode, false).callEvent(); // Paper - Brigadier API
-        net.minecraft.server.MinecraftServer.getServer().execute(() -> {
-           runSync(player, bukkit, rootcommandnode);
-        });
+        // Folia start - region threading
+        // ignore if retired
+        player.getBukkitEntity().taskScheduler.schedule((updatedPlayer) -> {
+           runSync((ServerPlayer)updatedPlayer, bukkit, rootcommandnode);
+        }, null, 1L);
+        // Folia end - region threading
     }
 
     private void runSync(ServerPlayer player, Collection<String> bukkit, RootCommandNode<SharedSuggestionProvider> rootcommandnode) {
diff --git a/src/main/java/net/minecraft/core/dispenser/AbstractProjectileDispenseBehavior.java b/src/main/java/net/minecraft/core/dispenser/AbstractProjectileDispenseBehavior.java
index bc2e763a848b4bf7e9598ffe1ca2aa35a9af4677..9496464d1400009d523b84373e8b47fdc1085ce3 100644
--- a/src/main/java/net/minecraft/core/dispenser/AbstractProjectileDispenseBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/AbstractProjectileDispenseBehavior.java
@@ -32,7 +32,7 @@ public abstract class AbstractProjectileDispenseBehavior extends DefaultDispense
         CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
         BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector((double) enumdirection.getStepX(), (double) ((float) enumdirection.getStepY() + 0.1F), (double) enumdirection.getStepZ()));
-        if (!DispenserBlock.eventFired) {
+        if (!DispenserBlock.eventFired.get()) { // Folia - region threading
             worldserver.getCraftServer().getPluginManager().callEvent(event);
         }
 
diff --git a/src/main/java/net/minecraft/core/dispenser/BoatDispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/BoatDispenseItemBehavior.java
index 6df0db8b4cdab23494ea34236949ece4989110a3..2fd670d941bd575f99def28732ffee29f37a3182 100644
--- a/src/main/java/net/minecraft/core/dispenser/BoatDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/BoatDispenseItemBehavior.java
@@ -63,7 +63,7 @@ public class BoatDispenseItemBehavior extends DefaultDispenseItemBehavior {
         CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
         BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(d1, d2 + d4, d3));
-        if (!DispenserBlock.eventFired) {
+        if (!DispenserBlock.eventFired.get()) { // Folia - region threading
             worldserver.getCraftServer().getPluginManager().callEvent(event);
         }
 
diff --git a/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java
index f28705547a62da790f5df071400986aacba39367..4bbed8e057a32ce22d768392cebc27110cf4338b 100644
--- a/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java
@@ -85,7 +85,7 @@ public class DefaultDispenseItemBehavior implements DispenseItemBehavior {
         CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack);
 
         BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), CraftVector.toBukkit(entityitem.getDeltaMovement()));
-        if (!DispenserBlock.eventFired) {
+        if (!DispenserBlock.eventFired.get()) { // Folia - region threading
             world.getCraftServer().getPluginManager().callEvent(event);
         }
 
diff --git a/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
index e2e1273d787536d2fe1bdbbf8af36eb5ac220599..bee5d0a0516fbae4f550c0a77fcca6afcff8675f 100644
--- a/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
@@ -222,7 +222,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(0, 0, 0));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -281,7 +281,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(0, 0, 0));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -338,7 +338,7 @@ public interface DispenseItemBehavior {
                     CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                     BlockDispenseArmorEvent event = new BlockDispenseArmorEvent(block, craftItem.clone(), (org.bukkit.craftbukkit.entity.CraftLivingEntity) list.get(0).getBukkitEntity());
-                    if (!DispenserBlock.eventFired) {
+                    if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                         world.getCraftServer().getPluginManager().callEvent(event);
                     }
 
@@ -394,7 +394,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseArmorEvent event = new BlockDispenseArmorEvent(block, craftItem.clone(), (org.bukkit.craftbukkit.entity.CraftLivingEntity) entityhorseabstract.getBukkitEntity());
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     world.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -468,7 +468,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseArmorEvent event = new BlockDispenseArmorEvent(block, craftItem.clone(), (org.bukkit.craftbukkit.entity.CraftLivingEntity) entityhorsechestedabstract.getBukkitEntity());
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     world.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -507,7 +507,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(enumdirection.getStepX(), enumdirection.getStepY(), enumdirection.getStepZ()));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -565,7 +565,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(d3, d4, d5));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -645,7 +645,7 @@ public interface DispenseItemBehavior {
                     CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - single item in event
 
                     BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(x, y, z));
-                    if (!DispenserBlock.eventFired) {
+                    if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                         worldserver.getCraftServer().getPluginManager().callEvent(event);
                     }
 
@@ -722,7 +722,7 @@ public interface DispenseItemBehavior {
                         CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - single item in event
 
                         BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(blockposition.getX(), blockposition.getY(), blockposition.getZ()));
-                        if (!DispenserBlock.eventFired) {
+                        if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                             worldserver.getCraftServer().getPluginManager().callEvent(event);
                         }
 
@@ -769,7 +769,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack); // Paper - ignore stack size on damageable items
 
                 BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(0, 0, 0));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -830,7 +830,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - single item in event
 
                 BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector(0, 0, 0));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -848,7 +848,8 @@ public interface DispenseItemBehavior {
                     }
                 }
 
-                worldserver.captureTreeGeneration = true;
+                io.papermc.paper.threadedregions.RegionizedWorldData worldData = worldserver.getCurrentWorldData(); // Folia - region threading
+                worldData.captureTreeGeneration = true; // Folia - region threading
                 // CraftBukkit end
 
                 if (!BoneMealItem.growCrop(stack, worldserver, blockposition) && !BoneMealItem.growWaterPlant(stack, worldserver, blockposition, (Direction) null)) {
@@ -857,13 +858,13 @@ public interface DispenseItemBehavior {
                     worldserver.levelEvent(1505, blockposition, 0);
                 }
                 // CraftBukkit start
-                worldserver.captureTreeGeneration = false;
-                if (worldserver.capturedBlockStates.size() > 0) {
-                    TreeType treeType = SaplingBlock.treeType;
-                    SaplingBlock.treeType = null;
+                worldData.captureTreeGeneration = false; // Folia - region threading
+                if (worldData.capturedBlockStates.size() > 0) { // Folia - region threading
+                    TreeType treeType = SaplingBlock.treeTypeRT.get(); // Folia - region threading
+                    SaplingBlock.treeTypeRT.set(null); // Folia - region threading
                     Location location = CraftLocation.toBukkit(blockposition, worldserver.getWorld());
-                    List<org.bukkit.block.BlockState> blocks = new java.util.ArrayList<>(worldserver.capturedBlockStates.values());
-                    worldserver.capturedBlockStates.clear();
+                    List<org.bukkit.block.BlockState> blocks = new java.util.ArrayList<>(worldData.capturedBlockStates.values()); // Folia - region threading
+                    worldData.capturedBlockStates.clear(); // Folia - region threading
                     StructureGrowEvent structureEvent = null;
                     if (treeType != null) {
                         structureEvent = new StructureGrowEvent(location, treeType, false, null, blocks);
@@ -899,7 +900,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
                 BlockDispenseEvent event = new BlockDispenseEvent(block, craftItem.clone(), new org.bukkit.util.Vector((double) blockposition.getX() + 0.5D, (double) blockposition.getY(), (double) blockposition.getZ() + 0.5D));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                    worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -956,7 +957,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - single item in event
 
                 BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(blockposition.getX(), blockposition.getY(), blockposition.getZ()));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -1005,7 +1006,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - single item in event
 
                 BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(blockposition.getX(), blockposition.getY(), blockposition.getZ()));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
@@ -1078,7 +1079,7 @@ public interface DispenseItemBehavior {
                 CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - only single item in event
 
                 BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(blockposition.getX(), blockposition.getY(), blockposition.getZ()));
-                if (!DispenserBlock.eventFired) {
+                if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                     worldserver.getCraftServer().getPluginManager().callEvent(event);
                 }
 
diff --git a/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java
index 8d65cdb013706a932c2c73231108b2810b99e1c7..728e2f00de43b5363fdee2d982acab2614e45bcb 100644
--- a/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/ShearsDispenseItemBehavior.java
@@ -40,7 +40,7 @@ public class ShearsDispenseItemBehavior extends OptionalDispenseItemBehavior {
         CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack); // Paper - ignore stack size on damageable items
 
         BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(0, 0, 0));
-        if (!DispenserBlock.eventFired) {
+        if (!DispenserBlock.eventFired.get()) { // Folia - region threading
             worldserver.getCraftServer().getPluginManager().callEvent(event);
         }
 
diff --git a/src/main/java/net/minecraft/core/dispenser/ShulkerBoxDispenseBehavior.java b/src/main/java/net/minecraft/core/dispenser/ShulkerBoxDispenseBehavior.java
index cb308808906a8cdb127df8284e106e00553473ca..05bc1f010b50e673e9a185d96e338baef7ccad03 100644
--- a/src/main/java/net/minecraft/core/dispenser/ShulkerBoxDispenseBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/ShulkerBoxDispenseBehavior.java
@@ -37,7 +37,7 @@ public class ShulkerBoxDispenseBehavior extends OptionalDispenseItemBehavior {
             CraftItemStack craftItem = CraftItemStack.asCraftMirror(stack.copyWithCount(1)); // Paper - single item in event
 
             BlockDispenseEvent event = new BlockDispenseEvent(bukkitBlock, craftItem.clone(), new org.bukkit.util.Vector(blockposition.getX(), blockposition.getY(), blockposition.getZ()));
-            if (!DispenserBlock.eventFired) {
+            if (!DispenserBlock.eventFired.get().booleanValue()) { // Folia - region threading
                 pointer.level().getCraftServer().getPluginManager().callEvent(event);
             }
 
diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index a536ebcf29d8ef0ed32863bd8d5e70f7a0636e8d..936f8663b23908ac5de2076401a5d508f88a0376 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -84,7 +84,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         return new DefaultEventLoopGroup(0, (new ThreadFactoryBuilder()).setNameFormat("Netty Local Client IO #%d").setDaemon(true).setUncaughtExceptionHandler(new net.minecraft.DefaultUncaughtExceptionHandlerWithName(LOGGER)).build()); // Paper
     });
     private final PacketFlow receiving;
-    private final Queue<WrappedConsumer> pendingActions = Queues.newConcurrentLinkedQueue();
+    private final Queue<WrappedConsumer> pendingActions = new ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<>(); // Folia - region threading - connection fixes
     public Channel channel;
     public SocketAddress address;
     // Spigot Start
@@ -99,7 +99,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     @Nullable
     private Component disconnectedReason;
     private boolean encrypted;
-    private boolean disconnectionHandled;
+    private final java.util.concurrent.atomic.AtomicBoolean disconnectionHandled = new java.util.concurrent.atomic.AtomicBoolean(false); // Folia - region threading - may be called concurrently during configuration stage
     private int receivedPackets;
     private int sentPackets;
     private float averageReceivedPackets;
@@ -153,6 +153,32 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         this.receiving = side;
     }
 
+    // Folia start - region threading
+    private volatile boolean becomeActive;
+
+    public boolean becomeActive() {
+        return this.becomeActive;
+    }
+
+    private static record DisconnectReq(Component disconnectReason, org.bukkit.event.player.PlayerKickEvent.Cause cause) {}
+
+    private final ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<DisconnectReq> disconnectReqs =
+        new ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<>();
+
+    /**
+     * Safely disconnects the connection while possibly on another thread. Note: This call will not block, even if on the
+     * same thread that could disconnect.
+     */
+    public final void disconnectSafely(Component disconnectReason, org.bukkit.event.player.PlayerKickEvent.Cause cause) {
+        this.disconnectReqs.add(new DisconnectReq(disconnectReason, cause));
+        // We can't halt packet processing here because a plugin could cancel a kick request.
+    }
+
+    public final boolean isPlayerConnected() {
+        return this.packetListener instanceof net.minecraft.server.network.ServerCommonPacketListenerImpl;
+    }
+    // Folia end - region threading
+
     public void channelActive(ChannelHandlerContext channelhandlercontext) throws Exception {
         super.channelActive(channelhandlercontext);
         this.channel = channelhandlercontext.channel();
@@ -163,7 +189,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         if (this.delayedDisconnect != null) {
             this.disconnect(this.delayedDisconnect);
         }
-
+        this.becomeActive = true; // Folia - region threading
     }
 
     public static void setInitialProtocolAttributes(Channel channel) {
@@ -387,7 +413,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         }
 
         packet.onPacketDispatch(this.getPlayer());
-        if (connected && (InnerUtil.canSendImmediate(this, packet)
+        if (false && connected && (InnerUtil.canSendImmediate(this, packet) // Folia - region threading - connection fixes
             || (io.papermc.paper.util.MCUtil.isMainThread() && packet.isReady() && this.pendingActions.isEmpty()
             && (packet.getExtraPackets() == null || packet.getExtraPackets().isEmpty())))) {
             this.sendPacket(packet, callbacks, flush);
@@ -416,11 +442,12 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     }
 
     public void runOnceConnected(Consumer<Connection> task) {
-        if (this.isConnected()) {
+        if (false && this.isConnected()) { // Folia - region threading - connection fixes
             this.flushQueue();
             task.accept(this);
         } else {
             this.pendingActions.add(new WrappedConsumer(task)); // Paper - Optimize network
+            this.flushQueue(); // Folia - region threading - connection fixes
         }
 
     }
@@ -479,10 +506,11 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     }
 
     public void flushChannel() {
-        if (this.isConnected()) {
+        if (false && this.isConnected()) { // Folia - region threading - connection fixes
             this.flush();
         } else {
             this.pendingActions.add(new WrappedConsumer(Connection::flush)); // Paper - Optimize network
+            this.flushQueue(); // Folia - region threading - connection fixes
         }
 
     }
@@ -517,53 +545,61 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
 
     // Paper start - Optimize network: Rewrite this to be safer if ran off main thread
     private boolean flushQueue() {
-        if (!this.isConnected()) {
-            return true;
-        }
-        if (io.papermc.paper.util.MCUtil.isMainThread()) {
-            return this.processQueue();
-        } else if (this.isPending) {
-            // Should only happen during login/status stages
-            synchronized (this.pendingActions) {
-                return this.processQueue();
-            }
-        }
-        return false;
+        return this.processQueue(); // Folia - region threading - connection fixes
+    }
+
+    // Folia start - region threading - connection fixes
+    // allow only one thread to be flushing the queue at once to ensure packets are written in the order they are sent
+    // into the queue
+    private final java.util.concurrent.atomic.AtomicBoolean flushingQueue = new java.util.concurrent.atomic.AtomicBoolean();
+
+    private static boolean canWrite(WrappedConsumer queued) {
+        return queued != null && (!(queued instanceof PacketSendAction packet) || packet.packet.isReady());
     }
 
+    private boolean canWritePackets() {
+        return canWrite(this.pendingActions.peek());
+    }
+    // Folia end - region threading - connection fixes
+
     private boolean processQueue() {
-        if (this.pendingActions.isEmpty()) {
+        // Folia start - region threading - connection fixes
+        if (!this.isConnected()) {
             return true;
         }
 
-        // If we are on main, we are safe here in that nothing else should be processing queue off main anymore
-        // But if we are not on main due to login/status, the parent is synchronized on packetQueue
-        final java.util.Iterator<WrappedConsumer> iterator = this.pendingActions.iterator();
-        while (iterator.hasNext()) {
-            final WrappedConsumer queued = iterator.next(); // poll -> peek
-
-            // Fix NPE (Spigot bug caused by handleDisconnection())
-            if (queued == null) {
-                return true;
-            }
+        while (this.canWritePackets()) {
+            final boolean set = this.flushingQueue.getAndSet(true);
+            try {
+                if (set) {
+                    // we didn't acquire the lock, break
+                    return false;
+                }
 
-            if (queued.isConsumed()) {
-                continue;
-            }
+                ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<WrappedConsumer> queue =
+                    (ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<WrappedConsumer>)this.pendingActions;
+                WrappedConsumer holder;
+                for (;;) {
+                    // synchronise so that queue clears appear atomic
+                    synchronized (queue) {
+                        holder = queue.pollIf(Connection::canWrite);
+                    }
+                    if (holder == null) {
+                        break;
+                    }
 
-            if (queued instanceof PacketSendAction packetSendAction) {
-                final Packet<?> packet = packetSendAction.packet;
-                if (!packet.isReady()) {
-                    return false;
+                    holder.accept(this);
                 }
-            }
 
-            iterator.remove();
-            if (queued.tryMarkConsumed()) {
-                queued.accept(this);
+            } finally {
+                if (!set) {
+                    this.flushingQueue.set(false);
+                }
             }
         }
+
         return true;
+        // Folia end - region threading - connection fixes
     }
     // Paper end - Optimize network
 
@@ -572,21 +608,41 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     private static int currTick; // Paper - Buffer joins to world
     public void tick() {
         this.flushQueue();
-        // Paper start - Buffer joins to world
-        if (Connection.currTick != net.minecraft.server.MinecraftServer.currentTick) {
-            Connection.currTick = net.minecraft.server.MinecraftServer.currentTick;
-            Connection.joinAttemptsThisTick = 0;
+        // Folia - this is broken
+        // Folia start - region threading
+        // handle disconnect requests, but only after flushQueue()
+        DisconnectReq disconnectReq;
+        while ((disconnectReq = this.disconnectReqs.poll()) != null) {
+            PacketListener packetlistener = this.packetListener;
+
+            if (packetlistener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl loginPacketListener) {
+                loginPacketListener.disconnect(disconnectReq.disconnectReason);
+                // this doesn't fail, so abort any further attempts
+                return;
+            } else if (packetlistener instanceof net.minecraft.server.network.ServerCommonPacketListenerImpl commonPacketListener) {
+                commonPacketListener.disconnect(disconnectReq.disconnectReason, disconnectReq.cause);
+                // may be cancelled by a plugin, if not cancelled then any further calls do nothing
+                continue;
+            } else {
+                // no idea what packet to send
+                this.disconnect(disconnectReq.disconnectReason);
+                this.setReadOnly();
+                return;
+            }
         }
-        // Paper end - Buffer joins to world
+        if (!this.isConnected()) {
+            // disconnected from above
+            this.handleDisconnection();
+            return;
+        }
+        // Folia end - region threading
         PacketListener packetlistener = this.packetListener;
 
         if (packetlistener instanceof TickablePacketListener) {
             TickablePacketListener tickablepacketlistener = (TickablePacketListener) packetlistener;
 
             // Paper start - Buffer joins to world
-            if (!(this.packetListener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl loginPacketListener)
-                || loginPacketListener.state != net.minecraft.server.network.ServerLoginPacketListenerImpl.State.VERIFYING
-                || Connection.joinAttemptsThisTick++ < MAX_PER_TICK) {
+            if (true) { // Folia - region threading
             // Paper start - detailed watchdog information
             net.minecraft.network.protocol.PacketUtils.packetProcessing.push(this.packetListener);
             try { // Paper end - detailed watchdog information
@@ -598,7 +654,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             // Paper end - Buffer joins to world
         }
 
-        if (!this.isConnected() && !this.disconnectionHandled) {
+        if (!this.isConnected()) {// Folia - region threading - it's fine to call if it is already handled, as it no longer logs
             this.handleDisconnection();
         }
 
@@ -644,6 +700,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             this.channel.close(); // We can't wait as this may be called from an event loop.
             this.disconnectedReason = disconnectReason;
         }
+        this.becomeActive = true; // Folia - region threading
 
     }
 
@@ -823,10 +880,10 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
 
     public void handleDisconnection() {
         if (this.channel != null && !this.channel.isOpen()) {
-            if (this.disconnectionHandled) {
+            if (this.disconnectionHandled.getAndSet(true)) { // Folia - region threading - may be called concurrently during configuration stage
                 // Connection.LOGGER.warn("handleDisconnection() called twice"); // Paper - Don't log useless message
             } else {
-                this.disconnectionHandled = true;
+                // Folia - region threading - may be called concurrently during configuration stage - set above
                 PacketListener packetlistener = this.getPacketListener();
                 PacketListener packetlistener1 = packetlistener != null ? packetlistener : this.disconnectListener;
 
@@ -858,6 +915,22 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
                     }
                 }
                 // Paper end - Add PlayerConnectionCloseEvent
+                // Folia start - region threading
+                if (packetlistener instanceof net.minecraft.server.network.ServerCommonPacketListenerImpl commonPacketListener) {
+                    net.minecraft.server.MinecraftServer.getServer().getPlayerList().removeConnection(
+                        commonPacketListener.getOwner().getName(),
+                        commonPacketListener.getOwner().getId(), this
+                    );
+                } else if (packetlistener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl loginPacketListener) {
+                    if (loginPacketListener.state.ordinal() >= net.minecraft.server.network.ServerLoginPacketListenerImpl.State.VERIFYING.ordinal()) {
+                        net.minecraft.server.MinecraftServer.getServer().getPlayerList().removeConnection(
+                            loginPacketListener.authenticatedProfile.getName(),
+                            loginPacketListener.authenticatedProfile.getId(), this
+                        );
+                    }
+                }
+                // Folia end - region threading
+                // Paper end
 
             }
         }
@@ -878,15 +951,25 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     // Paper start - Optimize network
     public void clearPacketQueue() {
         final net.minecraft.server.level.ServerPlayer player = getPlayer();
-        for (final Consumer<Connection> queuedAction : this.pendingActions) {
-            if (queuedAction instanceof PacketSendAction packetSendAction) {
-                final Packet<?> packet = packetSendAction.packet;
-                if (packet.hasFinishListener()) {
-                    packet.onPacketDispatchFinish(player, null);
+        // Folia start - region threading - connection fixes
+        java.util.List<Connection.PacketSendAction> queuedPackets = new java.util.ArrayList<>();
+        // synchronise so that flushQueue does not poll values while the queue is being cleared
+        synchronized (this.pendingActions) {
+            Connection.WrappedConsumer consumer;
+            while ((consumer = this.pendingActions.poll()) != null) {
+                if (consumer instanceof Connection.PacketSendAction packetHolder) {
+                    queuedPackets.add(packetHolder);
                 }
             }
         }
-        this.pendingActions.clear();
+
+        for (Connection.PacketSendAction queuedPacket : queuedPackets) {
+            Packet<?> packet = queuedPacket.packet;
+            if (packet.hasFinishListener()) {
+                packet.onPacketDispatchFinish(player, null);
+            }
+        }
+        // Folia end - region threading - connection fixes
     }
 
     private static class InnerUtil { // Attempt to hide these methods from ProtocolLib, so it doesn't accidently pick them up.
diff --git a/src/main/java/net/minecraft/network/protocol/PacketUtils.java b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
index 83302c252f54481f239522e5c6861ccfe233070a..1192503d2729b3f14aa2936c2060df9884870cb4 100644
--- a/src/main/java/net/minecraft/network/protocol/PacketUtils.java
+++ b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
@@ -44,7 +44,7 @@ public class PacketUtils {
 
     public static <T extends PacketListener> void ensureRunningOnSameThread(Packet<T> packet, T listener, BlockableEventLoop<?> engine) throws RunningOnDifferentThreadException {
         if (!engine.isSameThread()) {
-            engine.executeIfPossible(() -> {
+            Runnable run = () -> { // Folia - region threading
                 packetProcessing.push(listener); // Paper - detailed watchdog information
                 try { // Paper - detailed watchdog information
                 if (listener instanceof ServerCommonPacketListenerImpl serverCommonPacketListener && serverCommonPacketListener.processedDisconnect) return; // CraftBukkit - Don't handle sync packets for kicked players
@@ -91,7 +91,21 @@ public class PacketUtils {
                 }
                 // Paper end - detailed watchdog information
 
-            });
+            }; // Folia start - region threading
+            // ignore retired state, if removed then we don't want the packet to be handled
+            if (listener instanceof net.minecraft.server.network.ServerGamePacketListenerImpl gamePacketListener) {
+                gamePacketListener.player.getBukkitEntity().taskScheduler.schedule(
+                    (net.minecraft.server.level.ServerPlayer player) -> {
+                        run.run();
+                    },
+                    null, 1L
+                );
+            } else if (listener instanceof net.minecraft.server.network.ServerConfigurationPacketListenerImpl configurationPacketListener) {
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(run);
+            } else {
+                throw new UnsupportedOperationException("Unknown listener: " + listener);
+            }
+            // Folia end - region threading
             throw RunningOnDifferentThreadException.RUNNING_ON_DIFFERENT_THREAD;
         }
     }
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 6c42592bfaf85f23f7ff9966d7869aa0237f59c5..4e94de4a3184fd36119bf39beccff62ac561c1e4 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -203,7 +203,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     private static final int OVERLOADED_TICKS_THRESHOLD = 20;
     private static final long OVERLOADED_WARNING_INTERVAL_NANOS = 10L * TimeUtil.NANOSECONDS_PER_SECOND;
     private static final int OVERLOADED_TICKS_WARNING_INTERVAL = 100;
-    private static final long STATUS_EXPIRE_TIME_NANOS = 5L * TimeUtil.NANOSECONDS_PER_SECOND;
+    public static final long STATUS_EXPIRE_TIME_NANOS = 5L * TimeUtil.NANOSECONDS_PER_SECOND; // Folia - region threading - public
     private static final long PREPARE_LEVELS_DEFAULT_DELAY_NANOS = 10L * TimeUtil.NANOSECONDS_PER_MILLISECOND;
     private static final int MAX_STATUS_PLAYER_SAMPLE = 12;
     public static final int START_CHUNK_RADIUS = 11;
@@ -241,8 +241,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     private volatile boolean running;
     private volatile boolean isRestarting = false; // Paper - flag to signify we're attempting to restart
     private boolean stopped;
-    private int tickCount;
-    private int ticksUntilAutosave;
+    // Folia - region threading
     protected final Proxy proxy;
     private boolean onlineMode;
     private boolean preventProxyConnections;
@@ -292,7 +291,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public org.bukkit.craftbukkit.CraftServer server;
     public OptionSet options;
     public org.bukkit.command.ConsoleCommandSender console;
-    public static int currentTick; // Paper - improve tick loop
+    //public static int currentTick; // Paper - improve tick loop // Folia - region threading
     public java.util.Queue<Runnable> processQueue = new java.util.concurrent.ConcurrentLinkedQueue<Runnable>();
     public int autosavePeriod;
     public Commands vanillaCommandDispatcher;
@@ -306,13 +305,41 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public final double[] recentTps = new double[ 3 ];
     // Spigot end
     public final io.papermc.paper.configuration.PaperConfigurations paperConfigurations; // Paper - add paper configuration files
-    public static long currentTickLong = 0L; // Paper - track current tick as a long
+    //public static long currentTickLong = 0L; // Paper - track current tick as a long // Folia - threaded regions
     public boolean isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
 
     public volatile Thread shutdownThread; // Paper
     public volatile boolean abnormalExit = false; // Paper
     public static final long SERVER_INIT = System.nanoTime(); // Paper - Lag compensation
 
+    // Folia start - regionised ticking
+    public final io.papermc.paper.threadedregions.RegionizedServer regionizedServer = new io.papermc.paper.threadedregions.RegionizedServer();
+
+    @Override
+    public void execute(Runnable runnable) {
+        if (true) {
+            throw new UnsupportedOperationException();
+        }
+        super.execute(runnable);
+    }
+
+    @Override
+    public void executeBlocking(Runnable runnable) {
+        if (true) {
+            throw new UnsupportedOperationException();
+        }
+        super.executeBlocking(runnable);
+    }
+
+    @Override
+    public void tell(TickTask runnable) {
+        if (true) {
+            throw new UnsupportedOperationException();
+        }
+        super.tell(runnable);
+    }
+    // Folia end - regionised ticking
+
     public static <S extends MinecraftServer> S spin(Function<Thread, S> serverFactory) {
         AtomicReference<S> atomicreference = new AtomicReference();
         Thread thread = new io.papermc.paper.util.TickThread(() -> { // Paper - rewrite chunk system
@@ -348,7 +375,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         this.port = -1;
         this.levels = Maps.newLinkedHashMap();
         this.running = true;
-        this.ticksUntilAutosave = 6000;
+        // Folia - use absolute time instead of this
         this.tickTimesNanos = new long[100];
         this.aggregatedTickTimesNanos = 0L;
         this.nextTickTimeNanos = Util.getNanos();
@@ -638,7 +665,21 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
             worlddata.setModdedInfo(this.getServerModName(), this.getModdedStatus().shouldReportAsModified());
             this.addLevel(world); // Paper - Put world into worldlist before initing the world; move up
-            this.initWorld(world, worlddata, this.worldData, worldoptions);
+            // Folia start - region threading
+            // the spawn should be within ~32 blocks, so we force add ticket levels to ensure the first thread
+            // to init spawn will not run into any ownership issues
+            // move init to start of tickServer
+            int loadRegionRadius = ((32) >> 4);
+            world.randomSpawnSelection = new ChunkPos(world.getChunkSource().randomState().sampler().findSpawnPosition());
+            for (int currX = -loadRegionRadius; currX <= loadRegionRadius; ++currX) {
+                for (int currZ = -loadRegionRadius; currZ <= loadRegionRadius; ++currZ) {
+                    ChunkPos pos = new ChunkPos(currX, currZ);
+                    world.chunkSource.addTicketAtLevel(
+                        TicketType.UNKNOWN, pos, io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL, pos
+                    );
+                }
+            }
+            // Folia end - region threading
 
             // Paper - Put world into worldlist before initing the world; move up
             this.getPlayerList().addWorldborderListener(world);
@@ -650,6 +691,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         this.forceDifficulty();
         for (ServerLevel worldserver : this.getAllLevels()) {
             this.prepareLevels(worldserver.getChunkSource().chunkMap.progressListener, worldserver);
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addWorld(worldserver); // Folia - region threading
             //worldserver.entityManager.tick(); // SPIGOT-6526: Load pending entities so they are available to the API // Paper - rewrite chunk system, not required to "tick" anything
             this.server.getPluginManager().callEvent(new org.bukkit.event.world.WorldLoadEvent(worldserver.getWorld()));
         }
@@ -713,7 +755,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             worldProperties.setSpawn(BlockPos.ZERO.above(80), 0.0F);
         } else {
             ServerChunkCache chunkproviderserver = world.getChunkSource();
-            ChunkPos chunkcoordintpair = new ChunkPos(chunkproviderserver.randomState().sampler().findSpawnPosition());
+            ChunkPos chunkcoordintpair = world.randomSpawnSelection; // Folia - region threading
             // CraftBukkit start
             if (world.generator != null) {
                 Random rand = new Random(world.getSeed());
@@ -734,6 +776,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             if (i < world.getMinBuildHeight()) {
                 BlockPos blockposition = chunkcoordintpair.getWorldPosition();
 
+                world.getChunk(blockposition.offset(8, 0, 8)); // Folia - region threading - sync load first
                 i = world.getHeight(Heightmap.Types.WORLD_SURFACE, blockposition.getX() + 8, blockposition.getZ() + 8);
             }
 
@@ -814,7 +857,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end - Configurable Keep Spawn Loaded range per world
 
         // this.nextTickTimeNanos = SystemUtils.getNanos() + MinecraftServer.PREPARE_LEVELS_DEFAULT_DELAY_NANOS;
-        this.executeModerately();
+        //this.executeModerately(); // Folia - region threading
         // Iterator iterator = this.levels.values().iterator();
         } // Paper - Configurable Keep Spawn Loaded range per world
 
@@ -837,7 +880,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
         // CraftBukkit start
         // this.nextTickTimeNanos = SystemUtils.getNanos() + MinecraftServer.PREPARE_LEVELS_DEFAULT_DELAY_NANOS;
-        this.executeModerately();
+        //this.executeModerately(); // Folia - region threading
         // CraftBukkit end
         if (worldserver.getWorld().getKeepSpawnInMemory()) worldloadlistener.stop(); // Paper - Configurable Keep Spawn Loaded range per world
         // CraftBukkit start
@@ -941,7 +984,37 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
     // CraftBukkit end
 
+    // Folia start - region threading
+    private final java.util.concurrent.atomic.AtomicBoolean hasStartedShutdownThread = new java.util.concurrent.atomic.AtomicBoolean();
+
+    private void haltServerRegionThreading() {
+        if (this.hasStartedShutdownThread.getAndSet(true)) {
+            // already started shutdown
+            return;
+        }
+        new io.papermc.paper.threadedregions.RegionShutdownThread("Region shutdown thread").start();
+    }
+
+    public void haltCurrentRegion() {
+        if (!io.papermc.paper.util.TickThread.isShutdownThread()) {
+            throw new IllegalStateException();
+        }
+    }
+    // Folia end - region threading
+
     public void stopServer() {
+        // Folia start - region threading
+        // halt scheduler
+        // don't wait, we may be on a scheduler thread
+        io.papermc.paper.threadedregions.TickRegions.getScheduler().halt(false, 0L);
+        // cannot run shutdown logic on this thread, as it may be a scheduler
+        if (true) {
+            if (!io.papermc.paper.util.TickThread.isShutdownThread()) {
+                this.haltServerRegionThreading();
+                return;
+            } // else: fall through to regular stop logic
+        }
+        // Folia end - region threading
         // CraftBukkit start - prevent double stopping on multiple threads
         synchronized(this.stopLock) {
             if (this.hasStopped) return;
@@ -951,7 +1024,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper start - kill main thread, and kill it hard
         shutdownThread = Thread.currentThread();
         org.spigotmc.WatchdogThread.doStop(); // Paper
-        if (!isSameThread()) {
+        if (false && !isSameThread()) { // Folia - region threading
             MinecraftServer.LOGGER.info("Stopping main thread (Ignore any thread death message you see! - DO NOT REPORT THREAD DEATH TO PAPER)");
             while (this.getRunningThread().isAlive()) {
                 this.getRunningThread().stop();
@@ -978,12 +1051,19 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         this.getConnection().stop();
         this.isSaving = true;
         if (this.playerList != null) {
-            MinecraftServer.LOGGER.info("Saving players");
-            this.playerList.saveAll();
+            //MinecraftServer.LOGGER.info("Saving players"); // Folia - move to shutdown thread logic
+            //this.playerList.saveAll(); // Folia - move to shutdown thread logic
             this.playerList.removeAll(this.isRestarting); // Paper
             try { Thread.sleep(100); } catch (InterruptedException ex) {} // CraftBukkit - SPIGOT-625 - give server at least a chance to send packets
         }
 
+        // Folia start - region threading
+        if (true) {
+            // the rest till part 2 is handled by the region shutdown thread
+            return;
+        }
+        // Folia end - region threading
+
         MinecraftServer.LOGGER.info("Saving worlds");
         Iterator iterator = this.getAllLevels().iterator();
 
@@ -999,6 +1079,11 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         this.saveAllChunks(false, true, false, true); // Paper - rewrite chunk system - move closing into here
 
         this.isSaving = false;
+        // Folia start - region threading
+        this.stopPart2();
+    }
+    public void stopPart2() {
+        // Folia end - region threading
         this.resources.close();
 
         try {
@@ -1055,6 +1140,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         if (isDebugging()) io.papermc.paper.util.TraceUtil.dumpTraceForThread("Server stopped"); // Paper - Debugging
         // Paper end
         this.running = false;
+        this.stopServer(); // Folia - region threading
         if (waitForShutdown) {
             try {
                 this.serverThread.join();
@@ -1136,10 +1222,23 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             this.statusIcon = (ServerStatus.Favicon) this.loadStatusIcon().orElse(null); // CraftBukkit - decompile error
             this.status = this.buildServerStatus();
 
+            // Folia start - region threading
+            if (true) {
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().init(); // Folia - region threading - only after loading worlds
+                String doneTime = String.format(java.util.Locale.ROOT, "%.3fs", (double) (Util.getNanos() - serverStartTime) / 1.0E9D);
+                LOGGER.info("Done ({})! For help, type \"help\"", doneTime);
+                for (;;) {
+                    try {
+                        Thread.sleep(Long.MAX_VALUE);
+                    } catch (final InterruptedException ex) {}
+                }
+            }
+            // Folia end - region threading
+
             // Spigot start
             // Paper start - move done tracking
             LOGGER.info("Running delayed init tasks");
-            this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // run all 1 tick delay tasks during init,
+            //this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // run all 1 tick delay tasks during init, // Folia - region threading
             // this is going to be the first thing the tick process does anyways, so move done and run it after
             // everything is init before watchdog tick.
             // anything at 3+ won't be caught here but also will trip watchdog....
@@ -1192,10 +1291,10 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                     }
                 }
                 // Spigot start
-                ++MinecraftServer.currentTickLong; // Paper - track current tick as a long
+                //++MinecraftServer.currentTickLong; // Paper - track current tick as a long // Folia - region threading
                 // Paper start - further improve server tick loop
                 currentTime = Util.getNanos();
-                if (++MinecraftServer.currentTick % MinecraftServer.SAMPLE_INTERVAL == 0) {
+                if (false) { // Folia - region threading
                     final long diff = currentTime - tickSection;
                     final java.math.BigDecimal currentTps = TPS_BASE.divide(new java.math.BigDecimal(diff), 30, java.math.RoundingMode.HALF_UP);
                     tps1.add(currentTps, diff);
@@ -1215,7 +1314,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
                 if (this.debugCommandProfilerDelayStart) {
                     this.debugCommandProfilerDelayStart = false;
-                    this.debugCommandProfiler = new MinecraftServer.TimeProfiler(Util.getNanos(), this.tickCount);
+                    //this.debugCommandProfiler = new MinecraftServer.TimeProfiler(Util.getNanos(), this.tickCount); // Folia - region threading
                 }
 
                 //MinecraftServer.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit // Paper - don't overwrite current tick time
@@ -1223,9 +1322,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                 this.nextTickTimeNanos += i;
                 this.startMetricsRecordingTick();
                 this.profiler.push("tick");
-                this.tickServer(flag ? () -> {
-                    return false;
-                } : this::haveTime);
+                if (true) throw new UnsupportedOperationException(); // Folia - region threading
                 this.profiler.popPush("nextTickWait");
                 this.mayHaveDelayedTasks = true;
                 this.delayedTasksMaxNextTickTimeNanos = Math.max(Util.getNanos() + i, this.nextTickTimeNanos);
@@ -1347,21 +1444,16 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     @Override
     public TickTask wrapRunnable(Runnable runnable) {
-        // Paper start - anything that does try to post to main during watchdog crash, run on watchdog
-        if (this.hasStopped && Thread.currentThread().equals(shutdownThread)) {
-            runnable.run();
-            runnable = () -> {};
-        }
-        // Paper end
-        return new TickTask(this.tickCount, runnable);
+        throw new UnsupportedOperationException(); // Folia - region threading
     }
 
     protected boolean shouldRun(TickTask ticktask) {
-        return ticktask.getTick() + 3 < this.tickCount || this.haveTime();
+        throw new UnsupportedOperationException(); // Folia - region threading
     }
 
     @Override
     public boolean pollTask() {
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         boolean flag = this.pollTaskInternal();
 
         this.mayHaveDelayedTasks = flag;
@@ -1374,33 +1466,20 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     static final long TASK_EXECUTION_FAILURE_BACKOFF = 5L * 1000L; // 5us
 
-    private static long lastMidTickExecute;
-    private static long lastMidTickExecuteFailure;
-
-    private boolean tickMidTickTasks() {
-        // give all worlds a fair chance at by targetting them all.
-        // if we execute too many tasks, that's fine - we have logic to correctly handle overuse of allocated time.
-        boolean executed = false;
-        for (ServerLevel world : this.getAllLevels()) {
-            long currTime = System.nanoTime();
-            if (currTime - world.lastMidTickExecuteFailure <= TASK_EXECUTION_FAILURE_BACKOFF) {
-                continue;
-            }
-            if (!world.getChunkSource().pollTask()) {
-                // we need to back off if this fails
-                world.lastMidTickExecuteFailure = currTime;
-            } else {
-                executed = true;
-            }
-        }
+    // Folia - region threading
 
-        return executed;
+    // Folia start - region threading
+    private boolean tickMidTickTasks(io.papermc.paper.threadedregions.RegionizedWorldData worldData) { // Folia - region threading
+        // Folia - region threading - only execute for one world
+        return worldData.world.getChunkSource().pollTask();
     }
+    // Folia end - region threading
 
     public final void executeMidTickTasks() {
         org.spigotmc.AsyncCatcher.catchOp("mid tick chunk task execution");
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData(); // Folia - region threading
         long startTime = System.nanoTime();
-        if ((startTime - lastMidTickExecute) <= CHUNK_TASK_QUEUE_BACKOFF_MIN_TIME || (startTime - lastMidTickExecuteFailure) <= TASK_EXECUTION_FAILURE_BACKOFF) {
+        if ((startTime - worldData.lastMidTickExecute) <= CHUNK_TASK_QUEUE_BACKOFF_MIN_TIME || (startTime - worldData.lastMidTickExecuteFailure) <= TASK_EXECUTION_FAILURE_BACKOFF) { // Folia - region threading
             // it's shown to be bad to constantly hit the queue (chunk loads slow to a crawl), even if no tasks are executed.
             // so, backoff to prevent this
             return;
@@ -1409,13 +1488,13 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         co.aikar.timings.MinecraftTimings.midTickChunkTasks.startTiming();
         try {
             for (;;) {
-                boolean moreTasks = this.tickMidTickTasks();
+                boolean moreTasks = this.tickMidTickTasks(worldData); // Folia - region threading
                 long currTime = System.nanoTime();
                 long diff = currTime - startTime;
 
                 if (!moreTasks || diff >= MAX_CHUNK_EXEC_TIME) {
                     if (!moreTasks) {
-                        lastMidTickExecuteFailure = currTime;
+                        worldData.lastMidTickExecuteFailure = currTime; // Folia - region threading
                     }
 
                     // note: negative values reduce the time
@@ -1428,7 +1507,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                     double overuseCount = (double)overuse/(double)MAX_CHUNK_EXEC_TIME;
                     long extraSleep = (long)Math.round(overuseCount*CHUNK_TASK_QUEUE_BACKOFF_MIN_TIME);
 
-                    lastMidTickExecute = currTime + extraSleep;
+                    worldData.lastMidTickExecute = currTime + extraSleep; // Folia - region threading
                     return;
                 }
             }
@@ -1439,6 +1518,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     // Paper end - execute chunk tasks mid tick
 
     private boolean pollTaskInternal() {
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         if (super.pollTask()) {
             this.executeMidTickTasks(); // Paper - execute chunk tasks mid tick
             return true;
@@ -1461,6 +1541,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     public void doRunTask(TickTask ticktask) { // CraftBukkit - decompile error
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         this.getProfiler().incrementCounter("runTask");
         super.doRunTask(ticktask);
     }
@@ -1507,43 +1588,83 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         return false;
     }
 
-    public void tickServer(BooleanSupplier shouldKeepTicking) {
+    // Folia start - region threading
+    public void tickServer(long startTime, long scheduledEnd, long targetBuffer,
+                           io.papermc.paper.threadedregions.TickRegions.TickRegionData region) {
+        if (region != null) {
+            region.world.getCurrentWorldData().updateTickData();
+            if (region.world.checkInitialised.get() != ServerLevel.WORLD_INIT_CHECKED) {
+                synchronized (region.world.checkInitialised) {
+                    if (region.world.checkInitialised.compareAndSet(ServerLevel.WORLD_INIT_NOT_CHECKED, ServerLevel.WORLD_INIT_CHECKING)) {
+                        LOGGER.info("Initialising world '" + region.world.getWorld().getName() + "' before it can be ticked...");
+                        this.initWorld(region.world, region.world.serverLevelData, worldData, region.world.serverLevelData.worldGenOptions()); // Folia - delayed until first tick of world
+                        region.world.checkInitialised.set(ServerLevel.WORLD_INIT_CHECKED);
+                        LOGGER.info("Initialised world '" + region.world.getWorld().getName() + "'");
+                    } // else: must be checked
+                }
+            }
+        }
+        BooleanSupplier shouldKeepTicking = () -> {
+            return scheduledEnd - System.nanoTime() > targetBuffer;
+        };
+        new com.destroystokyo.paper.event.server.ServerTickStartEvent((int)region.getCurrentTick()).callEvent(); // Paper
+        // Folia end - region threading
         co.aikar.timings.TimingsManager.FULL_SERVER_TICK.startTiming(); // Paper
-        long i = Util.getNanos();
+        long i = startTime; // Folia - region threading
 
         // Paper start - move oversleep into full server tick
+        if (region == null) { // Folia - region threading
         isOversleep = true;MinecraftTimings.serverOversleep.startTiming();
         this.managedBlock(() -> {
             return !this.canOversleep();
         });
         isOversleep = false;MinecraftTimings.serverOversleep.stopTiming();
+        } // Folia - region threading
         // Paper end
-        new com.destroystokyo.paper.event.server.ServerTickStartEvent(this.tickCount+1).callEvent(); // Paper - Server Tick Events
+        // Folia - region threading - move up
+
+        // Folia start - region threading
+        if (region != null) {
+            region.getTaskQueueData().drainTasks();
+            ((io.papermc.paper.threadedregions.scheduler.FoliaRegionScheduler)Bukkit.getRegionScheduler()).tick();
+            // now run all the entity schedulers
+            // TODO there has got to be a more efficient variant of this crap
+            for (Entity entity : region.world.getCurrentWorldData().getLocalEntitiesCopy()) {
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(entity) || entity.isRemoved()) {
+                    continue;
+                }
+                org.bukkit.craftbukkit.entity.CraftEntity bukkit = entity.getBukkitEntityRaw();
+                if (bukkit != null) {
+                    bukkit.taskScheduler.executeTick();
+                }
+            }
+        }
+        // Folia end - region threading
 
-        ++this.tickCount;
-        this.tickRateManager.tick();
-        this.tickChildren(shouldKeepTicking);
-        if (i - this.lastServerStatus >= MinecraftServer.STATUS_EXPIRE_TIME_NANOS) {
+        // Folia - region threading
+        if (region == null) this.tickRateManager.tick(); // Folia - region threading
+        this.tickChildren(shouldKeepTicking, region); // Folia - region threading
+        if (region == null && i - this.lastServerStatus >= MinecraftServer.STATUS_EXPIRE_TIME_NANOS) { // Folia - region threading
             this.lastServerStatus = i;
             this.status = this.buildServerStatus();
         }
 
-        --this.ticksUntilAutosave;
+        // Folia - region threading
         // Paper start - Incremental chunk and player saving
         int playerSaveInterval = io.papermc.paper.configuration.GlobalConfiguration.get().playerAutoSave.rate;
         if (playerSaveInterval < 0) {
             playerSaveInterval = autosavePeriod;
         }
         this.profiler.push("save");
-        final boolean fullSave = autosavePeriod > 0 && this.tickCount % autosavePeriod == 0;
+        final boolean fullSave = autosavePeriod > 0 && io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() % autosavePeriod == 0; // Folia - region threading
         try {
             this.isSaving = true;
             if (playerSaveInterval > 0) {
                 this.playerList.saveAll(playerSaveInterval);
             }
-            for (ServerLevel level : this.getAllLevels()) {
+            for (ServerLevel level : (region == null ? this.getAllLevels() : Arrays.asList(region.world))) { // Folia - region threading
                 if (level.paperConfig().chunks.autoSaveInterval.value() > 0) {
-                    level.saveIncrementally(fullSave);
+                    level.saveIncrementally(region == null && fullSave); // Folia - region threading - don't save level.dat
                 }
             }
         } finally {
@@ -1553,63 +1674,37 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end - Incremental chunk and player saving
         io.papermc.paper.util.CachedLists.reset(); // Paper
         // Paper start - move executeAll() into full server tick timing
-        try (co.aikar.timings.Timing ignored = MinecraftTimings.processTasksTimer.startTiming()) {
+        if (region == null) try (co.aikar.timings.Timing ignored = MinecraftTimings.processTasksTimer.startTiming()) { // Folia - region threading
             this.runAllTasks();
         }
         // Paper end
         // Paper start - Server Tick Events
         long endTime = System.nanoTime();
-        long remaining = (TICK_TIME - (endTime - lastTick)) - catchupTime;
-        new com.destroystokyo.paper.event.server.ServerTickEndEvent(this.tickCount, ((double)(endTime - lastTick) / 1000000D), remaining).callEvent();
+        long remaining = scheduledEnd - endTime; // Folia - region ticking
+        new com.destroystokyo.paper.event.server.ServerTickEndEvent((int)io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick(), ((double)(endTime - startTime) / 1000000D), remaining).callEvent(); // Folia - region ticking
         // Paper end - Server Tick Events
         this.profiler.push("tallying");
-        long j = Util.getNanos() - i;
-        int k = this.tickCount % 100;
-
-        this.aggregatedTickTimesNanos -= this.tickTimesNanos[k];
-        this.aggregatedTickTimesNanos += j;
-        this.tickTimesNanos[k] = j;
-        this.smoothedTickTimeMillis = this.smoothedTickTimeMillis * 0.8F + (float) j / (float) TimeUtil.NANOSECONDS_PER_MILLISECOND * 0.19999999F;
-        long l = Util.getNanos();
-
-        // Paper start - Add tick times API and /mspt command
-        tickTimes5s.add(this.tickCount, j);
-        tickTimes10s.add(this.tickCount, j);
-        tickTimes60s.add(this.tickCount, j);
-        // Paper end - Add tick times API and /mspt command
-        this.logTickTime(l - i);
+        // Folia - region threading
         this.profiler.pop();
         org.spigotmc.WatchdogThread.tick(); // Spigot
         co.aikar.timings.TimingsManager.FULL_SERVER_TICK.stopTiming(); // Paper
     }
 
-    private int computeNextAutosaveInterval() {
-        float f;
-
-        if (this.tickRateManager.isSprinting()) {
-            long i = this.getAverageTickTimeNanos() + 1L;
-
-            f = (float) TimeUtil.NANOSECONDS_PER_SECOND / (float) i;
-        } else {
-            f = this.tickRateManager.tickrate();
-        }
-
-        boolean flag = true;
-
-        return Math.max(100, (int) (f * 300.0F));
-    }
+    // Folia - region threading - use absolute time instead of this
 
     public void onTickRateChanged() {
-        int i = this.computeNextAutosaveInterval();
-
-        if (i < this.ticksUntilAutosave) {
-            this.ticksUntilAutosave = i;
-        }
+        // Folia - region threading - use absolute time instead of this
 
     }
 
     protected void logTickTime(long nanos) {}
 
+    // Folia start - region threading
+    public void rebuildServerStatus() {
+        this.status = this.buildServerStatus();
+    }
+    // Folia end - region threading
+
     private ServerStatus buildServerStatus() {
         ServerStatus.Players serverping_serverpingplayersample = this.buildPlayerStatus();
 
@@ -1617,7 +1712,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     private ServerStatus.Players buildPlayerStatus() {
-        List<ServerPlayer> list = this.playerList.getPlayers();
+        List<ServerPlayer> list = new java.util.ArrayList<>(this.playerList.getPlayers()); // Folia - region threading
         int i = this.getMaxPlayers();
 
         if (this.hidesOnlinePlayers()) {
@@ -1638,31 +1733,18 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         }
     }
 
-    public void tickChildren(BooleanSupplier shouldKeepTicking) {
-        this.getPlayerList().getPlayers().forEach((entityplayer) -> {
+    public void tickChildren(BooleanSupplier shouldKeepTicking, io.papermc.paper.threadedregions.TickRegions.TickRegionData region) { // Folia - region threading
+        final io.papermc.paper.threadedregions.RegionizedWorldData regionizedWorldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData(); // Folia - regionised ticking
+        if (region == null) this.getPlayerList().getPlayers().forEach((entityplayer) -> { // Folia - region threading
             entityplayer.connection.suspendFlushing();
         });
         MinecraftTimings.bukkitSchedulerTimer.startTiming(); // Spigot // Paper
-        this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // CraftBukkit
+        // Folia - region threading
         MinecraftTimings.bukkitSchedulerTimer.stopTiming(); // Spigot // Paper
-        // Paper start - Folia scheduler API
-        ((io.papermc.paper.threadedregions.scheduler.FoliaGlobalRegionScheduler) Bukkit.getGlobalRegionScheduler()).tick();
-        getAllLevels().forEach(level -> {
-            for (final Entity entity : level.getEntityLookup().getAllCopy()) { // Paper - rewrite chunk system
-                if (entity.isRemoved()) {
-                    continue;
-                }
-                final org.bukkit.craftbukkit.entity.CraftEntity bukkit = entity.getBukkitEntityRaw();
-                if (bukkit != null) {
-                    bukkit.taskScheduler.executeTick();
-                }
-            }
-        });
-        // Paper end - Folia scheduler API
-        io.papermc.paper.adventure.providers.ClickCallbackProviderImpl.CALLBACK_MANAGER.handleQueue(this.tickCount); // Paper
+        // Folia - region threading - moved to global tick - and moved entity scheduler to tickRegion
         this.profiler.push("commandFunctions");
         MinecraftTimings.commandFunctionsTimer.startTiming(); // Spigot // Paper
-        this.getFunctions().tick();
+        if (region == null) this.getFunctions().tick(); // Folia - region threading - TODO Purge functions
         MinecraftTimings.commandFunctionsTimer.stopTiming(); // Spigot // Paper
         this.profiler.popPush("levels");
         //Iterator iterator = this.getAllLevels().iterator(); // Paper - Throw exception on world create while being ticked; moved down
@@ -1670,7 +1752,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // CraftBukkit start
         // Run tasks that are waiting on processing
         MinecraftTimings.processQueueTimer.startTiming(); // Spigot
-        while (!this.processQueue.isEmpty()) {
+        if (region == null) while (!this.processQueue.isEmpty()) { // Folia - region threading
             this.processQueue.remove().run();
         }
         MinecraftTimings.processQueueTimer.stopTiming(); // Spigot
@@ -1678,13 +1760,13 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         MinecraftTimings.timeUpdateTimer.startTiming(); // Spigot // Paper
         // Send time updates to everyone, it will get the right time from the world the player is in.
         // Paper start - Perf: Optimize time updates
-        for (final ServerLevel level : this.getAllLevels()) {
+        for (final ServerLevel level : (region == null ? this.getAllLevels() : Arrays.asList(region.world))) { // Folia - region threading
             final boolean doDaylight = level.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT);
             final long dayTime = level.getDayTime();
             long worldTime = level.getGameTime();
             final ClientboundSetTimePacket worldPacket = new ClientboundSetTimePacket(worldTime, dayTime, doDaylight);
-            for (Player entityhuman : level.players()) {
-                if (!(entityhuman instanceof ServerPlayer) || (tickCount + entityhuman.getId()) % 20 != 0) {
+            for (Player entityhuman : level.getLocalPlayers()) { // Folia - region threading
+                if (!(entityhuman instanceof ServerPlayer) || (io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + entityhuman.getId()) % 20 != 0) { // Folia - region threading
                     continue;
                 }
                 ServerPlayer entityplayer = (ServerPlayer) entityhuman;
@@ -1697,14 +1779,11 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end - Perf: Optimize time updates
         MinecraftTimings.timeUpdateTimer.stopTiming(); // Spigot // Paper
 
-        this.isIteratingOverLevels = true; // Paper - Throw exception on world create while being ticked
-        Iterator iterator = this.getAllLevels().iterator(); // Paper - Throw exception on world create while being ticked; move down
+        if (region == null) this.isIteratingOverLevels = true; // Paper - Throw exception on world create while being ticked // Folia - region threading
+        Iterator iterator = region == null ? this.getAllLevels().iterator() : Arrays.asList(region.world).iterator(); // Paper - Throw exception on world create while being ticked; move down // Folia - region threading
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
-            worldserver.hasPhysicsEvent = org.bukkit.event.block.BlockPhysicsEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - BlockPhysicsEvent
-            worldserver.hasEntityMoveEvent = io.papermc.paper.event.entity.EntityMoveEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper - Add EntityMoveEvent
-            net.minecraft.world.level.block.entity.HopperBlockEntity.skipHopperEvents = worldserver.paperConfig().hopper.disableMoveEvent || org.bukkit.event.inventory.InventoryMoveItemEvent.getHandlerList().getRegisteredListeners().length == 0; // Paper - Perf: Optimize Hoppers
-            worldserver.updateLagCompensationTick(); // Paper - lag compensation
+            // Folia - region threading
 
             this.profiler.push(() -> {
                 return worldserver + " " + worldserver.dimension().location();
@@ -1721,7 +1800,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
             try {
                 worldserver.timings.doTick.startTiming(); // Spigot
-                worldserver.tick(shouldKeepTicking);
+                worldserver.tick(shouldKeepTicking, region); // Folia - region threading
                 // Paper start
                 for (final io.papermc.paper.chunk.SingleThreadChunkRegionManager regionManager : worldserver.getChunkSource().chunkMap.regionManagers) {
                     regionManager.recalculateRegions();
@@ -1737,17 +1816,18 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
             this.profiler.pop();
             this.profiler.pop();
-            worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions
+            regionizedWorldData.explosionDensityCache.clear(); // Paper - Optimize explosions // Folia - region threading
         }
-        this.isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked
+        if (region == null) this.isIteratingOverLevels = false; // Paper - Throw exception on world create while being ticked // Folia - region threading
 
         this.profiler.popPush("connection");
         MinecraftTimings.connectionTimer.startTiming(); // Spigot // Paper
-        this.getConnection().tick();
+        if (region == null) this.getConnection().tick(); // Folia - region threading
+        if (region != null) regionizedWorldData.tickConnections(); // Folia - region threading
         MinecraftTimings.connectionTimer.stopTiming(); // Spigot // Paper
         this.profiler.popPush("players");
         MinecraftTimings.playerListTimer.startTiming(); // Spigot // Paper
-        this.playerList.tick();
+        if (false) this.playerList.tick(); // Folia - region threading
         MinecraftTimings.playerListTimer.stopTiming(); // Spigot // Paper
         if (SharedConstants.IS_RUNNING_IN_IDE && this.tickRateManager.runsNormally()) {
             GameTestTicker.SINGLETON.tick();
@@ -1756,7 +1836,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         this.profiler.popPush("server gui refresh");
 
         MinecraftTimings.tickablesTimer.startTiming(); // Spigot // Paper
-        for (int i = 0; i < this.tickables.size(); ++i) {
+        if (region == null) for (int i = 0; i < this.tickables.size(); ++i) {  // Folia - region threading - TODO WTF is this?
             ((Runnable) this.tickables.get(i)).run();
         }
         MinecraftTimings.tickablesTimer.stopTiming(); // Spigot // Paper
@@ -1764,7 +1844,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         this.profiler.popPush("send chunks");
         iterator = this.playerList.getPlayers().iterator();
 
-        while (iterator.hasNext()) {
+        if (region == null) while (iterator.hasNext()) { // Folia - region threading
             ServerPlayer entityplayer = (ServerPlayer) iterator.next();
 
             entityplayer.connection.chunkSender.sendNextChunks(entityplayer);
@@ -2107,7 +2187,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     public int getTickCount() {
-        return this.tickCount;
+        throw new UnsupportedOperationException(); // Folia - region threading
     }
 
     public int getSpawnProtectionRadius() {
@@ -2162,6 +2242,15 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     public void invalidateStatus() {
+        // Folia start - region threading
+        if (true) {
+            // we don't need this to notify the global tick region
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTaskWithoutNotify(() -> {
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().invalidateStatus();
+            });
+            return;
+        }
+        // Folia end - region threading
         this.lastServerStatus = 0L;
     }
 
@@ -2176,6 +2265,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     @Override
     public void executeIfPossible(Runnable runnable) {
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         if (this.isStopped()) {
             throw new io.papermc.paper.util.ServerStopRejectedExecutionException("Server already shutting down"); // Paper - do not prematurely disconnect players on stop
         } else {
@@ -2434,7 +2524,12 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     public long getAverageTickTimeNanos() {
-        return this.aggregatedTickTimesNanos / (long) Math.min(100, Math.max(this.tickCount, 1));
+        // Folia start - region threading
+        if (io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentTickingTask() instanceof io.papermc.paper.threadedregions.TickRegionScheduler.RegionScheduleHandle handle) {
+            return (long)Math.ceil(handle.getTickReport5s(System.nanoTime()).timePerTickData().segmentAll().average());
+        }
+        return 0L;
+        // Folia end - region threading
     }
 
     public long[] getTickTimesNanos() {
@@ -2793,14 +2888,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     public ProfileResults stopTimeProfiler() {
-        if (this.debugCommandProfiler == null) {
-            return EmptyProfileResults.EMPTY;
-        } else {
-            ProfileResults methodprofilerresults = this.debugCommandProfiler.stop(Util.getNanos(), this.tickCount);
-
-            this.debugCommandProfiler = null;
-            return methodprofilerresults;
-        }
+        throw new UnsupportedOperationException(); // Folia - region threading
     }
 
     public int getMaxChainedNeighborUpdates() {
diff --git a/src/main/java/net/minecraft/server/commands/AdvancementCommands.java b/src/main/java/net/minecraft/server/commands/AdvancementCommands.java
index b12ec4d70a2bd43617d26893f7d46c54ed23d893..2757dcdcb806ff5bf42b964f494eec70c0ffb795 100644
--- a/src/main/java/net/minecraft/server/commands/AdvancementCommands.java
+++ b/src/main/java/net/minecraft/server/commands/AdvancementCommands.java
@@ -268,7 +268,12 @@ public class AdvancementCommands {
         int i = 0;
 
         for (ServerPlayer serverPlayer : targets) {
-            i += operation.perform(serverPlayer, selection);
+            // Folia start - region threading
+            i += 1;
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                operation.perform(player, selection);
+            }, null, 1L);
+            // Folia end - region threading
         }
 
         if (i == 0) {
@@ -332,9 +337,12 @@ public class AdvancementCommands {
             throw ERROR_CRITERION_NOT_FOUND.create(Advancement.name(advancement), criterion);
         } else {
             for (ServerPlayer serverPlayer : targets) {
-                if (operation.performCriterion(serverPlayer, advancement, criterion)) {
-                    i++;
-                }
+                // Folia start - region threading
+                ++i;
+                serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                    operation.performCriterion(player, advancement, criterion);
+                }, null, 1L);
+                // Folia end - region threading
             }
 
             if (i == 0) {
diff --git a/src/main/java/net/minecraft/server/commands/AttributeCommand.java b/src/main/java/net/minecraft/server/commands/AttributeCommand.java
index 152ac7b347a1b85d65eb8a28ec9e85fd77484d31..a6b0b41fafe2993ceeaaea77605beb589eb9bd75 100644
--- a/src/main/java/net/minecraft/server/commands/AttributeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/AttributeCommand.java
@@ -239,27 +239,59 @@ public class AttributeCommand {
         }
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int getAttributeValue(CommandSourceStack source, Entity target, Holder<Attribute> attribute, double multiplier) throws CommandSyntaxException {
-        LivingEntity livingEntity = getEntityWithAttribute(target, attribute);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        LivingEntity livingEntity = getEntityWithAttribute(nmsEntity, attribute); // Folia - region threading
         double d = livingEntity.getAttributeValue(attribute);
-        source.sendSuccess(() -> Component.translatable("commands.attribute.value.get.success", getAttributeDescription(attribute), target.getName(), d), false);
-        return (int)(d * multiplier);
+        source.sendSuccess(() -> Component.translatable("commands.attribute.value.get.success", getAttributeDescription(attribute), nmsEntity.getName(), d), false); // Folia - region threading
+        return; // Folia - region threading
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 
     private static int getAttributeBase(CommandSourceStack source, Entity target, Holder<Attribute> attribute, double multiplier) throws CommandSyntaxException {
-        LivingEntity livingEntity = getEntityWithAttribute(target, attribute);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        LivingEntity livingEntity = getEntityWithAttribute(nmsEntity, attribute); // Folia - region threading
         double d = livingEntity.getAttributeBaseValue(attribute);
         source.sendSuccess(
-            () -> Component.translatable("commands.attribute.base_value.get.success", getAttributeDescription(attribute), target.getName(), d), false
+            () -> Component.translatable("commands.attribute.base_value.get.success", getAttributeDescription(attribute), nmsEntity.getName(), d), false // Folia - region threading
         );
-        return (int)(d * multiplier);
+        return; // Folia - region threading
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 
     private static int getAttributeModifier(CommandSourceStack source, Entity target, Holder<Attribute> attribute, UUID uuid, double multiplier) throws CommandSyntaxException {
-        LivingEntity livingEntity = getEntityWithAttribute(target, attribute);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        LivingEntity livingEntity = getEntityWithAttribute(nmsEntity, attribute); // Folia - region threading
         AttributeMap attributeMap = livingEntity.getAttributes();
         if (!attributeMap.hasModifier(attribute, uuid)) {
-            throw ERROR_NO_SUCH_MODIFIER.create(target.getName(), getAttributeDescription(attribute), uuid);
+            throw ERROR_NO_SUCH_MODIFIER.create(nmsEntity.getName(), getAttributeDescription(attribute), uuid); // Folia - region threading
         } else {
             double d = attributeMap.getModifierValue(attribute, uuid);
             source.sendSuccess(
@@ -267,55 +299,95 @@ public class AttributeCommand {
                         "commands.attribute.modifier.value.get.success",
                         Component.translationArg(uuid),
                         getAttributeDescription(attribute),
-                        target.getName(),
+                        nmsEntity.getName(), // Folia - region threading
                         d
                     ),
                 false
             );
-            return (int)(d * multiplier);
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 
     private static int setAttributeBase(CommandSourceStack source, Entity target, Holder<Attribute> attribute, double value) throws CommandSyntaxException {
-        getAttributeInstance(target, attribute).setBaseValue(value);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        getAttributeInstance(nmsEntity, attribute).setBaseValue(value); // Folia - region threading
         source.sendSuccess(
-            () -> Component.translatable("commands.attribute.base_value.set.success", getAttributeDescription(attribute), target.getName(), value), false
+            () -> Component.translatable("commands.attribute.base_value.set.success", getAttributeDescription(attribute), nmsEntity.getName(), value), false // Folia - region threading
         );
-        return 1;
+        return; // Folia - region threading
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 
     private static int addModifier(
         CommandSourceStack source, Entity target, Holder<Attribute> attribute, UUID uuid, String name, double value, AttributeModifier.Operation operation
     ) throws CommandSyntaxException {
-        AttributeInstance attributeInstance = getAttributeInstance(target, attribute);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        AttributeInstance attributeInstance = getAttributeInstance(nmsEntity, attribute); // Folia - region threading
         AttributeModifier attributeModifier = new AttributeModifier(uuid, name, value, operation);
         if (attributeInstance.hasModifier(attributeModifier)) {
-            throw ERROR_MODIFIER_ALREADY_PRESENT.create(target.getName(), getAttributeDescription(attribute), uuid);
+            throw ERROR_MODIFIER_ALREADY_PRESENT.create(nmsEntity.getName(), getAttributeDescription(attribute), uuid); // Folia - region threading
         } else {
             attributeInstance.addPermanentModifier(attributeModifier);
             source.sendSuccess(
                 () -> Component.translatable(
-                        "commands.attribute.modifier.add.success", Component.translationArg(uuid), getAttributeDescription(attribute), target.getName()
+                        "commands.attribute.modifier.add.success", Component.translationArg(uuid), getAttributeDescription(attribute), nmsEntity.getName() // Folia - region threading
                     ),
                 false
             );
-            return 1;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 
     private static int removeModifier(CommandSourceStack source, Entity target, Holder<Attribute> attribute, UUID uuid) throws CommandSyntaxException {
-        AttributeInstance attributeInstance = getAttributeInstance(target, attribute);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        AttributeInstance attributeInstance = getAttributeInstance(nmsEntity, attribute); // Folia - region threading
         if (attributeInstance.removePermanentModifier(uuid)) {
             source.sendSuccess(
                 () -> Component.translatable(
-                        "commands.attribute.modifier.remove.success", Component.translationArg(uuid), getAttributeDescription(attribute), target.getName()
+                        "commands.attribute.modifier.remove.success", Component.translationArg(uuid), getAttributeDescription(attribute), nmsEntity.getName() // Folia - region threading
                     ),
                 false
             );
-            return 1;
+            return; // Folia - region threading
         } else {
-            throw ERROR_NO_SUCH_MODIFIER.create(target.getName(), getAttributeDescription(attribute), uuid);
+            throw ERROR_NO_SUCH_MODIFIER.create(nmsEntity.getName(), getAttributeDescription(attribute), uuid); // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 
     private static Component getAttributeDescription(Holder<Attribute> attribute) {
diff --git a/src/main/java/net/minecraft/server/commands/ClearInventoryCommands.java b/src/main/java/net/minecraft/server/commands/ClearInventoryCommands.java
index 64ea52a5402f252165a5d8bf4fbd4ec257e7558e..af49f41e9a4e07e32c5de8edad4d2be7c9b19088 100644
--- a/src/main/java/net/minecraft/server/commands/ClearInventoryCommands.java
+++ b/src/main/java/net/minecraft/server/commands/ClearInventoryCommands.java
@@ -62,9 +62,14 @@ public class ClearInventoryCommands {
         int i = 0;
 
         for (ServerPlayer serverPlayer : targets) {
-            i += serverPlayer.getInventory().clearOrCountMatchingItems(item, maxCount, serverPlayer.inventoryMenu.getCraftSlots());
-            serverPlayer.containerMenu.broadcastChanges();
-            serverPlayer.inventoryMenu.slotsChanged(serverPlayer.getInventory());
+            // Folia start - region threading
+            ++i;
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                player.getInventory().clearOrCountMatchingItems(item, maxCount, player.inventoryMenu.getCraftSlots());
+                player.containerMenu.broadcastChanges();
+                player.inventoryMenu.slotsChanged(player.getInventory());
+            }, null, 1L);
+            // Folia end - region threading
         }
 
         if (i == 0) {
diff --git a/src/main/java/net/minecraft/server/commands/DamageCommand.java b/src/main/java/net/minecraft/server/commands/DamageCommand.java
index 43121f35a944fd9f8d4c5f1cc53749e79892478e..737c815cb0453b2bfafd59857c443e1cf333c23f 100644
--- a/src/main/java/net/minecraft/server/commands/DamageCommand.java
+++ b/src/main/java/net/minecraft/server/commands/DamageCommand.java
@@ -104,12 +104,29 @@ public class DamageCommand {
         );
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int damage(CommandSourceStack source, Entity target, float amount, DamageSource damageSource) throws CommandSyntaxException {
-        if (target.hurt(damageSource, amount)) {
-            source.sendSuccess(() -> Component.translatable("commands.damage.success", amount, target.getDisplayName()), true);
-            return 1;
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((Entity nmsEntity) -> {
+            try {
+                // Folia end - region threading
+        if (nmsEntity.hurt(damageSource, amount)) { // Folia - region threading
+            source.sendSuccess(() -> Component.translatable("commands.damage.success", amount, nmsEntity.getDisplayName()), true); // Folia - region threading
+            return; // Folia - region threading
         } else {
             throw ERROR_INVULNERABLE.create();
         }
+        // Folia start - region threading
+        } catch (CommandSyntaxException ex) {
+            sendMessage(source, ex);
+        }
+        }, null, 1L);
+        return 0;
+        // Folia end - region threading
     }
 }
diff --git a/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java b/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
index a046a0b1519806ff3d987e6402f152b60a3a6f4c..60649ced046fa126ef59b7a2dc3e6b5eeaf42bc4 100644
--- a/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
+++ b/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
@@ -28,12 +28,14 @@ public class DefaultGameModeCommands {
         GameType gameType = minecraftServer.getForcedGameType();
         if (gameType != null) {
             for (ServerPlayer serverPlayer : minecraftServer.getPlayerList().getPlayers()) {
+                serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
                 // Paper start - Expand PlayerGameModeChangeEvent
-                org.bukkit.event.player.PlayerGameModeChangeEvent event = serverPlayer.setGameMode(gameType, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.DEFAULT_GAMEMODE, net.kyori.adventure.text.Component.empty());
+                org.bukkit.event.player.PlayerGameModeChangeEvent event = player.setGameMode(gameType, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.DEFAULT_GAMEMODE, net.kyori.adventure.text.Component.empty()); // Folia - region threading
                 if (event != null && event.isCancelled()) {
                     source.sendSuccess(() -> io.papermc.paper.adventure.PaperAdventure.asVanilla(event.cancelMessage()), false);
                 }
                 // Paper end - Expand PlayerGameModeChangeEvent
+                }, null, 1L); // Folia - region threading
                     i++;
             }
         }
diff --git a/src/main/java/net/minecraft/server/commands/EffectCommands.java b/src/main/java/net/minecraft/server/commands/EffectCommands.java
index ebe50e2e69d346ce9266ed3f180d91ceb58008bd..227acbe74ff009c9275542af734852e3044b111b 100644
--- a/src/main/java/net/minecraft/server/commands/EffectCommands.java
+++ b/src/main/java/net/minecraft/server/commands/EffectCommands.java
@@ -84,7 +84,15 @@ public class EffectCommands {
             if (entity instanceof LivingEntity) {
                 MobEffectInstance mobeffect = new MobEffectInstance(mobeffectlist, k, amplifier, false, showParticles);
 
-                if (((LivingEntity) entity).addEffect(mobeffect, source.getEntity(), org.bukkit.event.entity.EntityPotionEffectEvent.Cause.COMMAND)) { // CraftBukkit
+                // Folia start - region threading
+                entity.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> {
+                    if (!(nmsEntity instanceof LivingEntity)) {
+                        return;
+                    }
+                    ((LivingEntity) nmsEntity).addEffect(mobeffect, null, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.COMMAND);
+                }, null, 1L);
+                // Folia end - region threading
+                if (true) { // CraftBukkit // Folia - region threading
                     ++j;
                 }
             }
@@ -114,8 +122,16 @@ public class EffectCommands {
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
 
-            if (entity instanceof LivingEntity && ((LivingEntity) entity).removeAllEffects(org.bukkit.event.entity.EntityPotionEffectEvent.Cause.COMMAND)) { // CraftBukkit
+            if (entity instanceof LivingEntity) { // CraftBukkit // Folia - region threading
                 ++i;
+                // Folia start - region threading
+                entity.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> {
+                    if (!(nmsEntity instanceof LivingEntity)) {
+                        return;
+                    }
+                    ((LivingEntity) nmsEntity).removeAllEffects(org.bukkit.event.entity.EntityPotionEffectEvent.Cause.COMMAND);
+                }, null, 1L);
+                // Folia end - region threading
             }
         }
 
@@ -144,8 +160,16 @@ public class EffectCommands {
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
 
-            if (entity instanceof LivingEntity && ((LivingEntity) entity).removeEffect(mobeffectlist, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.COMMAND)) { // CraftBukkit
+            if (entity instanceof LivingEntity) { // CraftBukkit // Folia - region threading
                 ++i;
+                // Folia start - region threading
+                entity.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> {
+                    if (!(nmsEntity instanceof LivingEntity)) {
+                        return;
+                    }
+                    ((LivingEntity) nmsEntity).removeEffect(mobeffectlist, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.COMMAND);
+                }, null, 1L);
+                // Folia end - region threading
             }
         }
 
diff --git a/src/main/java/net/minecraft/server/commands/EnchantCommand.java b/src/main/java/net/minecraft/server/commands/EnchantCommand.java
index 15bfe2e58d16864af29b04c17181ebf45fa21eba..3844b593c918a1f41c48acd1a3231eb43b483e41 100644
--- a/src/main/java/net/minecraft/server/commands/EnchantCommand.java
+++ b/src/main/java/net/minecraft/server/commands/EnchantCommand.java
@@ -68,49 +68,76 @@ public class EnchantCommand {
         );
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int enchant(CommandSourceStack source, Collection<? extends Entity> targets, Holder<Enchantment> enchantment, int level) throws CommandSyntaxException {
         Enchantment enchantment2 = enchantment.value();
         if (level > enchantment2.getMaxLevel()) {
             throw ERROR_LEVEL_TOO_HIGH.create(level, enchantment2.getMaxLevel());
         } else {
-            int i = 0;
+            final java.util.concurrent.atomic.AtomicInteger changed = new java.util.concurrent.atomic.AtomicInteger(0); // Folia - region threading
+            final java.util.concurrent.atomic.AtomicInteger count = new java.util.concurrent.atomic.AtomicInteger(targets.size()); // Folia - region threading
+            final java.util.concurrent.atomic.AtomicReference<Component> possibleSingleDisplayName = new java.util.concurrent.atomic.AtomicReference<>(); // Folia - region threading
 
             for (Entity entity : targets) {
                 if (entity instanceof LivingEntity) {
-                    LivingEntity livingEntity = (LivingEntity)entity;
-                    ItemStack itemStack = livingEntity.getMainHandItem();
-                    if (!itemStack.isEmpty()) {
-                        if (enchantment2.canEnchant(itemStack)
-                            && EnchantmentHelper.isEnchantmentCompatible(EnchantmentHelper.getEnchantments(itemStack).keySet(), enchantment2)) {
-                            itemStack.enchant(enchantment2, level);
-                            i++;
-                        } else if (targets.size() == 1) {
-                            throw ERROR_INCOMPATIBLE.create(itemStack.getItem().getName(itemStack).getString());
+                    // Folia start - region threading
+                    entity.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+                        try {
+                            LivingEntity livingEntity = (LivingEntity)nmsEntity;
+                            ItemStack itemStack = livingEntity.getMainHandItem();
+                            if (!itemStack.isEmpty()) {
+                                if (enchantment2.canEnchant(itemStack)
+                                    && EnchantmentHelper.isEnchantmentCompatible(EnchantmentHelper.getEnchantments(itemStack).keySet(), enchantment2)) {
+                                    itemStack.enchant(enchantment2, level);
+                                    possibleSingleDisplayName.set(livingEntity.getDisplayName());
+                                    changed.incrementAndGet();
+                                } else if (targets.size() == 1) {
+                                    throw ERROR_INCOMPATIBLE.create(itemStack.getItem().getName(itemStack).getString());
+                                }
+                            } else if (targets.size() == 1) {
+                                throw ERROR_NO_ITEM.create(livingEntity.getName().getString());
+                            }
+                        } catch (final CommandSyntaxException exception) {
+                            sendMessage(source, exception);
+                            return; // don't send feedback twice
                         }
-                    } else if (targets.size() == 1) {
-                        throw ERROR_NO_ITEM.create(livingEntity.getName().getString());
-                    }
+                        sendFeedback(source, enchantment2, level, possibleSingleDisplayName, count, changed);
+                    }, ignored -> sendFeedback(source, enchantment2, level, possibleSingleDisplayName, count, changed), 1L);
                 } else if (targets.size() == 1) {
                     throw ERROR_NOT_LIVING_ENTITY.create(entity.getName().getString());
+                } else {
+                    sendFeedback(source, enchantment2, level, possibleSingleDisplayName, count, changed);
+                    // Folia end - region threading
                 }
             }
+            return targets.size(); // Folia - region threading
+        }
+    }
 
+    // Folia start - region threading
+    private static void sendFeedback(final CommandSourceStack source, final Enchantment enchantment2, final int level, final java.util.concurrent.atomic.AtomicReference<Component> possibleSingleDisplayName, final java.util.concurrent.atomic.AtomicInteger count, final java.util.concurrent.atomic.AtomicInteger changed) {
+        if (count.decrementAndGet() == 0) {
+            final int i = changed.get();
             if (i == 0) {
-                throw ERROR_NOTHING_HAPPENED.create();
+                sendMessage(source, ERROR_NOTHING_HAPPENED.create());
             } else {
-                if (targets.size() == 1) {
+                if (i == 1) {
                     source.sendSuccess(
                         () -> Component.translatable(
-                                "commands.enchant.success.single", enchantment2.getFullname(level), targets.iterator().next().getDisplayName()
+                                "commands.enchant.success.single", enchantment2.getFullname(level), possibleSingleDisplayName.get()
                             ),
                         true
                     );
                 } else {
-                    source.sendSuccess(() -> Component.translatable("commands.enchant.success.multiple", enchantment2.getFullname(level), targets.size()), true);
+                    source.sendSuccess(() -> Component.translatable("commands.enchant.success.multiple", enchantment2.getFullname(level), i), true);
                 }
-
-                return i;
             }
         }
     }
+    // Folia end - region threading
 }
diff --git a/src/main/java/net/minecraft/server/commands/ExperienceCommand.java b/src/main/java/net/minecraft/server/commands/ExperienceCommand.java
index 337c2fe92a2727d3b0b9a0387c2ccaa2cbd48e9f..a795b750118845720b6aa101ab1e2f8ee37a91ed 100644
--- a/src/main/java/net/minecraft/server/commands/ExperienceCommand.java
+++ b/src/main/java/net/minecraft/server/commands/ExperienceCommand.java
@@ -131,14 +131,18 @@ public class ExperienceCommand {
     }
 
     private static int queryExperience(CommandSourceStack source, ServerPlayer player, ExperienceCommand.Type component) {
-        int i = component.query.applyAsInt(player);
-        source.sendSuccess(() -> Component.translatable("commands.experience.query." + component.name, player.getDisplayName(), i), false);
-        return i;
+        player.getBukkitEntity().taskScheduler.schedule((ServerPlayer serverPlayer) -> { // Folia - region threading
+        int i = component.query.applyAsInt(serverPlayer); // Folia - region threading
+        source.sendSuccess(() -> Component.translatable("commands.experience.query." + component.name, serverPlayer.getDisplayName(), i), false); // Folia - region threading
+        }, null, 1L); // Folia - region threading
+        return 0; // Folia - region threading
     }
 
     private static int addExperience(CommandSourceStack source, Collection<? extends ServerPlayer> targets, int amount, ExperienceCommand.Type component) {
         for (ServerPlayer serverPlayer : targets) {
-            component.add.accept(serverPlayer, amount);
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
+                component.add.accept(player, amount); // Folia - region threading
+            }, null, 1L); // Folia - region threading
         }
 
         if (targets.size() == 1) {
@@ -159,9 +163,11 @@ public class ExperienceCommand {
         int i = 0;
 
         for (ServerPlayer serverPlayer : targets) {
-            if (component.set.test(serverPlayer, amount)) {
-                i++;
+            ++i; serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
+            if (component.set.test(player, amount)) { // Folia - region threading
+                // Folia - region threading
             }
+            }, null, 1L); // Folia - region threading
         }
 
         if (i == 0) {
diff --git a/src/main/java/net/minecraft/server/commands/FillBiomeCommand.java b/src/main/java/net/minecraft/server/commands/FillBiomeCommand.java
index 6fbb6d215cffe12b8476eca1497698fdd5ac4111..d9056196b99ada4186e6642e0860727abd237a36 100644
--- a/src/main/java/net/minecraft/server/commands/FillBiomeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/FillBiomeCommand.java
@@ -106,6 +106,16 @@ public class FillBiomeCommand {
         });
     }
 
+    // Folia start - region threading
+    private static void sendMessage(Consumer<Supplier<Component>> src, Supplier<Either<Integer, CommandSyntaxException>> supplier) {
+        Either<Integer, CommandSyntaxException> either = supplier.get();
+        CommandSyntaxException ex = either == null ? null : either.right().orElse(null);
+        if (ex != null) {
+            src.accept(() -> (Component)ex.getRawMessage());
+        }
+    }
+    // Folia end - region threading
+
     public static Either<Integer, CommandSyntaxException> fill(
         ServerLevel world, BlockPos from, BlockPos to, Holder<Biome> biome, Predicate<Holder<Biome>> filter, Consumer<Supplier<Component>> feedbackConsumer
     ) {
@@ -117,6 +127,17 @@ public class FillBiomeCommand {
         if (i > j) {
             return Either.right(ERROR_VOLUME_TOO_LARGE.create(j, i));
         } else {
+            // Folia start - region threading
+            int buffer = 0; // no buffer, we do not touch neighbours
+            world.loadChunksAsync(
+                (boundingBox.minX() - buffer) >> 4,
+                (boundingBox.maxX() + buffer) >> 4,
+                (boundingBox.minZ() - buffer) >> 4,
+                (boundingBox.maxZ() + buffer) >> 4,
+                net.minecraft.world.level.chunk.ChunkStatus.FULL,
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+                (chunks) -> {
+                    sendMessage(feedbackConsumer, () -> {
             List<ChunkAccess> list = new ArrayList<>();
 
             for (int k = SectionPos.blockToSectionCoord(boundingBox.minZ()); k <= SectionPos.blockToSectionCoord(boundingBox.maxZ()); k++) {
@@ -153,6 +174,11 @@ public class FillBiomeCommand {
                     )
             );
             return Either.left(mutableInt.getValue());
+            // Folia start - region threading
+                    }); // sendMessage
+                    }); // loadChunksASync
+            return Either.left(Integer.valueOf(0));
+            // Folia end - region threading
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/commands/FillCommand.java b/src/main/java/net/minecraft/server/commands/FillCommand.java
index 4f61284c0d4ad6cd1b485956f5185552fd7800f8..67c313dedf354b09bb782d60e70673e08f17e03d 100644
--- a/src/main/java/net/minecraft/server/commands/FillCommand.java
+++ b/src/main/java/net/minecraft/server/commands/FillCommand.java
@@ -151,6 +151,12 @@ public class FillCommand {
         );
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int fillBlocks(
         CommandSourceStack source, BoundingBox range, BlockInput block, FillCommand.Mode mode, @Nullable Predicate<BlockInWorld> filter
     ) throws CommandSyntaxException {
@@ -161,6 +167,18 @@ public class FillCommand {
         } else {
             List<BlockPos> list = Lists.newArrayList();
             ServerLevel serverLevel = source.getLevel();
+            // Folia start - region threading
+            int buffer = 32;
+            // physics may spill into neighbour chunks, so use a buffer
+            serverLevel.loadChunksAsync(
+                (range.minX() - buffer) >> 4,
+                (range.maxX() + buffer) >> 4,
+                (range.minZ() - buffer) >> 4,
+                (range.maxZ() + buffer) >> 4,
+                net.minecraft.world.level.chunk.ChunkStatus.FULL,
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+                (chunks) -> {
+                    try { // Folia end - region threading
             int k = 0;
 
             for (BlockPos blockPos : BlockPos.betweenClosed(range.minX(), range.minY(), range.minZ(), range.maxX(), range.maxY(), range.maxZ())) {
@@ -187,8 +205,13 @@ public class FillCommand {
             } else {
                 int l = k;
                 source.sendSuccess(() -> Component.translatable("commands.fill.success", l), true);
-                return k;
+                return; // Folia - region threading
             }
+            // Folia start - region threading
+                } catch (CommandSyntaxException ex) {
+                    sendMessage(source, ex);
+                }
+            }); return 0; // Folia end - region threading
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/commands/ForceLoadCommand.java b/src/main/java/net/minecraft/server/commands/ForceLoadCommand.java
index 2e6d55f5582310038db10ace47bc10e171359634..fdd27cbc02ac58c2a2d85c0db00fa347073e915f 100644
--- a/src/main/java/net/minecraft/server/commands/ForceLoadCommand.java
+++ b/src/main/java/net/minecraft/server/commands/ForceLoadCommand.java
@@ -97,7 +97,17 @@ public class ForceLoadCommand {
         );
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int queryForceLoad(CommandSourceStack source, ColumnPos pos) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+        // Folia end - region threading
         ChunkPos chunkPos = pos.toChunkPos();
         ServerLevel serverLevel = source.getLevel();
         ResourceKey<Level> resourceKey = serverLevel.dimension();
@@ -109,14 +119,22 @@ public class ForceLoadCommand {
                     ),
                 false
             );
-            return 1;
+            return; // Folia - region threading
         } else {
             throw ERROR_NOT_TICKING.create(chunkPos, resourceKey.location());
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int listForceLoad(CommandSourceStack source) {
         ServerLevel serverLevel = source.getLevel();
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         ResourceKey<Level> resourceKey = serverLevel.dimension();
         LongSet longSet = serverLevel.getForcedChunks();
         int i = longSet.size();
@@ -134,20 +152,27 @@ public class ForceLoadCommand {
         } else {
             source.sendFailure(Component.translatable("commands.forceload.added.none", Component.translationArg(resourceKey.location())));
         }
+        }); // Folia - region threading
 
-        return i;
+        return 1; // Folia - region threading
     }
 
     private static int removeAll(CommandSourceStack source) {
         ServerLevel serverLevel = source.getLevel();
         ResourceKey<Level> resourceKey = serverLevel.dimension();
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         LongSet longSet = serverLevel.getForcedChunks();
         longSet.forEach(chunkPos -> serverLevel.setChunkForced(ChunkPos.getX(chunkPos), ChunkPos.getZ(chunkPos), false));
         source.sendSuccess(() -> Component.translatable("commands.forceload.removed.all", Component.translationArg(resourceKey.location())), true);
+        }); // Folia - region threading
         return 0;
     }
 
     private static int changeForceLoad(CommandSourceStack source, ColumnPos from, ColumnPos to, boolean forceLoaded) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+        // Folia end - region threading
         int i = Math.min(from.x(), to.x());
         int j = Math.min(from.z(), to.z());
         int k = Math.max(from.x(), to.x());
@@ -206,11 +231,18 @@ public class ForceLoadCommand {
                         );
                     }
 
-                    return r;
+                    return; // Folia - region threading
                 }
             }
         } else {
             throw BlockPosArgument.ERROR_OUT_OF_WORLD.create();
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 }
diff --git a/src/main/java/net/minecraft/server/commands/GameModeCommand.java b/src/main/java/net/minecraft/server/commands/GameModeCommand.java
index d1da3600dc07107309b20ebe6e7c0c4da0e8de76..a2075133b0e8ea6299dec0fa5125e4296eb3276a 100644
--- a/src/main/java/net/minecraft/server/commands/GameModeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/GameModeCommand.java
@@ -60,15 +60,18 @@ public class GameModeCommand {
         int i = 0;
 
         for (ServerPlayer serverPlayer : targets) {
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
             // Paper start - Expand PlayerGameModeChangeEvent
             org.bukkit.event.player.PlayerGameModeChangeEvent event = serverPlayer.setGameMode(gameMode, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.COMMAND, net.kyori.adventure.text.Component.empty());
             if (event != null && !event.isCancelled()) {
                 logGamemodeChange(context.getSource(), serverPlayer, gameMode);
-                i++;
+                // Folia - region threading
             } else if (event != null && event.cancelMessage() != null) {
                 context.getSource().sendSuccess(() -> io.papermc.paper.adventure.PaperAdventure.asVanilla(event.cancelMessage()), true);
                 // Paper end - Expand PlayerGameModeChangeEvent
             }
+            }, null, 1L); // Folia - region threading
+            ++i; // Folia - region threading
         }
 
         return i;
diff --git a/src/main/java/net/minecraft/server/commands/GiveCommand.java b/src/main/java/net/minecraft/server/commands/GiveCommand.java
index 1b459a8ee8a6bc039e742d65796bc76660a1c765..4efd0b529ee0431fb4dc76a950ab8f98856f622b 100644
--- a/src/main/java/net/minecraft/server/commands/GiveCommand.java
+++ b/src/main/java/net/minecraft/server/commands/GiveCommand.java
@@ -56,6 +56,7 @@ public class GiveCommand {
 
                     l -= i1;
                     ItemStack itemstack1 = item.createItemStack(i1, false);
+                    entityplayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
                     boolean flag = entityplayer.getInventory().add(itemstack1);
                     ItemEntity entityitem;
 
@@ -75,6 +76,7 @@ public class GiveCommand {
                             entityitem.setTarget(entityplayer.getUUID());
                         }
                     }
+                    }, null, 1L); // Folia - region threading
                 }
             }
 
diff --git a/src/main/java/net/minecraft/server/commands/KillCommand.java b/src/main/java/net/minecraft/server/commands/KillCommand.java
index c2974a6bd6851b54d1df2689195d896baf4906ee..57f5c571e63355b0e32480f31b9e5c8173d840c6 100644
--- a/src/main/java/net/minecraft/server/commands/KillCommand.java
+++ b/src/main/java/net/minecraft/server/commands/KillCommand.java
@@ -24,7 +24,9 @@ public class KillCommand {
 
     private static int kill(CommandSourceStack source, Collection<? extends Entity> targets) {
         for (Entity entity : targets) {
-            entity.kill();
+            entity.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
+                nmsEntity.kill(); // Folia - region threading
+            }, null, 1L); // Folia - region threading
         }
 
         if (targets.size() == 1) {
diff --git a/src/main/java/net/minecraft/server/commands/PlaceCommand.java b/src/main/java/net/minecraft/server/commands/PlaceCommand.java
index a78ac2c2a536abb0a77371c3d8a9ce0dc5084c38..4f0c962231562c13be8980f98a7d801ab292ab38 100644
--- a/src/main/java/net/minecraft/server/commands/PlaceCommand.java
+++ b/src/main/java/net/minecraft/server/commands/PlaceCommand.java
@@ -88,12 +88,25 @@ public class PlaceCommand {
         })))))))));
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     public static int placeFeature(CommandSourceStack source, Holder.Reference<ConfiguredFeature<?, ?>> feature, BlockPos pos) throws CommandSyntaxException {
         ServerLevel worldserver = source.getLevel();
         ConfiguredFeature<?, ?> worldgenfeatureconfigured = (ConfiguredFeature) feature.value();
         ChunkPos chunkcoordintpair = new ChunkPos(pos);
 
         PlaceCommand.checkLoaded(worldserver, new ChunkPos(chunkcoordintpair.x - 1, chunkcoordintpair.z - 1), new ChunkPos(chunkcoordintpair.x + 1, chunkcoordintpair.z + 1));
+        // Folia start - region threading
+        worldserver.loadChunksAsync(
+            pos, 16, net.minecraft.world.level.chunk.ChunkStatus.FULL,
+            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+            (chunks) -> {
+                try {
+        // Folia end - region threading
         if (!worldgenfeatureconfigured.place(worldserver, worldserver.getChunkSource().getGenerator(), worldserver.getRandom(), pos)) {
             throw PlaceCommand.ERROR_FEATURE_FAILED.create();
         } else {
@@ -102,27 +115,57 @@ public class PlaceCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.place.feature.success", s, pos.getX(), pos.getY(), pos.getZ());
             }, true);
-            return 1;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+                } catch (CommandSyntaxException ex) {
+                    sendMessage(source, ex);
+                }
+            }
+        );
+        return 1;
+        // Folia end - region threading
     }
 
     public static int placeJigsaw(CommandSourceStack source, Holder<StructureTemplatePool> structurePool, ResourceLocation id, int maxDepth, BlockPos pos) throws CommandSyntaxException {
         ServerLevel worldserver = source.getLevel();
 
+        // Folia start - region threading
+        worldserver.loadChunksAsync(
+            pos, 16, net.minecraft.world.level.chunk.ChunkStatus.FULL,
+            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+            (chunks) -> {
+                try {
+        // Folia end - region threading
         if (!JigsawPlacement.generateJigsaw(worldserver, structurePool, id, maxDepth, pos, false)) {
             throw PlaceCommand.ERROR_JIGSAW_FAILED.create();
         } else {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.place.jigsaw.success", pos.getX(), pos.getY(), pos.getZ());
             }, true);
-            return 1;
+            return; // Folia start - region threading
         }
+        // Folia start - region threading
+                } catch (CommandSyntaxException ex) {
+                    sendMessage(source, ex);
+                }
+            }
+        );
+        return 1;
+        // Folia end - region threading
     }
 
     public static int placeStructure(CommandSourceStack source, Holder.Reference<Structure> structure, BlockPos pos) throws CommandSyntaxException {
         ServerLevel worldserver = source.getLevel();
         Structure structure1 = (Structure) structure.value();
         ChunkGenerator chunkgenerator = worldserver.getChunkSource().getGenerator();
+        // Folia start - region threading
+        worldserver.loadChunksAsync(
+            pos, 16, net.minecraft.world.level.chunk.ChunkStatus.FULL,
+            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+            (chunks) -> {
+                try {
+        // Folia end - region threading
         StructureStart structurestart = structure1.generate(source.registryAccess(), chunkgenerator, chunkgenerator.getBiomeSource(), worldserver.getChunkSource().randomState(), worldserver.getStructureManager(), worldserver.getSeed(), new ChunkPos(pos), 0, worldserver, (holder) -> {
             return true;
         });
@@ -144,12 +187,27 @@ public class PlaceCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.place.structure.success", s, pos.getX(), pos.getY(), pos.getZ());
             }, true);
-            return 1;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+                } catch (CommandSyntaxException ex) {
+                    sendMessage(source, ex);
+                }
+            }
+        );
+        return 1;
+        // Folia end - region threading
     }
 
     public static int placeTemplate(CommandSourceStack source, ResourceLocation id, BlockPos pos, Rotation rotation, Mirror mirror, float integrity, int seed) throws CommandSyntaxException {
         ServerLevel worldserver = source.getLevel();
+        // Folia start - region threading
+        worldserver.loadChunksAsync(
+            pos, 16, net.minecraft.world.level.chunk.ChunkStatus.FULL,
+            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+            (chunks) -> {
+                try {
+        // Folia end - region threading
         StructureTemplateManager structuretemplatemanager = worldserver.getStructureManager();
 
         Optional optional;
@@ -180,9 +238,17 @@ public class PlaceCommand {
                 source.sendSuccess(() -> {
                     return Component.translatable("commands.place.template.success", Component.translationArg(id), pos.getX(), pos.getY(), pos.getZ());
                 }, true);
-                return 1;
+                return; // Folia - region threading
             }
         }
+        // Folia start - region threading
+                } catch (CommandSyntaxException ex) {
+                    sendMessage(source, ex);
+                }
+            }
+        );
+        return 1;
+        // Folia end - region threading
     }
 
     private static void checkLoaded(ServerLevel world, ChunkPos pos1, ChunkPos pos2) throws CommandSyntaxException {
diff --git a/src/main/java/net/minecraft/server/commands/RecipeCommand.java b/src/main/java/net/minecraft/server/commands/RecipeCommand.java
index 869eceace975ae0a14e6be27f4c0d0e77afd715a..f8635a3beb5433269e3e7b7dc6c7f456783fd939 100644
--- a/src/main/java/net/minecraft/server/commands/RecipeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/RecipeCommand.java
@@ -83,7 +83,12 @@ public class RecipeCommand {
         int i = 0;
 
         for (ServerPlayer serverPlayer : targets) {
-            i += serverPlayer.awardRecipes(recipes);
+            // Folia start - region threading
+            ++i;
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                player.awardRecipes(recipes);
+            }, null, 1L);
+            // Folia end - region threading
         }
 
         if (i == 0) {
@@ -105,7 +110,12 @@ public class RecipeCommand {
         int i = 0;
 
         for (ServerPlayer serverPlayer : targets) {
-            i += serverPlayer.resetRecipes(recipes);
+            // Folia start - region threading
+            ++i;
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                player.resetRecipes(recipes);
+            }, null, 1L);
+            // Folia end - region threading
         }
 
         if (i == 0) {
diff --git a/src/main/java/net/minecraft/server/commands/SetBlockCommand.java b/src/main/java/net/minecraft/server/commands/SetBlockCommand.java
index 977f3b1f0b6822d37254452c681717d31d3e1011..ea13a3b409b8a4a6a77071c700b4dd0a33b02716 100644
--- a/src/main/java/net/minecraft/server/commands/SetBlockCommand.java
+++ b/src/main/java/net/minecraft/server/commands/SetBlockCommand.java
@@ -80,10 +80,21 @@ public class SetBlockCommand {
         );
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int setBlock(
         CommandSourceStack source, BlockPos pos, BlockInput block, SetBlockCommand.Mode mode, @Nullable Predicate<BlockInWorld> condition
     ) throws CommandSyntaxException {
         ServerLevel serverLevel = source.getLevel();
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+            serverLevel, pos.getX() >> 4, pos.getZ() >> 4, () -> {
+                try {
+                    // Folia end - region threading
         if (condition != null && !condition.test(new BlockInWorld(serverLevel, pos, true))) {
             throw ERROR_FAILED.create();
         } else {
@@ -102,9 +113,16 @@ public class SetBlockCommand {
             } else {
                 serverLevel.blockUpdated(pos, block.getState().getBlock());
                 source.sendSuccess(() -> Component.translatable("commands.setblock.success", pos.getX(), pos.getY(), pos.getZ()), true);
-                return 1;
+                return; // Folia - region threading
             }
         }
+        // Folia start - region threading
+                } catch (CommandSyntaxException ex) {
+                    sendMessage(source, ex);
+                }
+            });
+        return 1;
+        // Folia end - region threading
     }
 
     public interface Filter {
diff --git a/src/main/java/net/minecraft/server/commands/SetSpawnCommand.java b/src/main/java/net/minecraft/server/commands/SetSpawnCommand.java
index 15db9368227dbc29d07d74e85bd126b345b526b6..161ae9c5f9ff0e8cdf3bb3c6bb1d068607f9c2ad 100644
--- a/src/main/java/net/minecraft/server/commands/SetSpawnCommand.java
+++ b/src/main/java/net/minecraft/server/commands/SetSpawnCommand.java
@@ -43,7 +43,11 @@ public class SetSpawnCommand {
             ServerPlayer entityplayer = (ServerPlayer) iterator.next();
 
             // Paper start - Add PlayerSetSpawnEvent
-            if (entityplayer.setRespawnPosition(resourcekey, pos, angle, true, false, com.destroystokyo.paper.event.player.PlayerSetSpawnEvent.Cause.COMMAND)) {
+            // Folia start - region threading
+            entityplayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                player.setRespawnPosition(resourcekey, pos, angle, true, false, com.destroystokyo.paper.event.player.PlayerSetSpawnEvent.Cause.COMMAND);
+            }, null, 1L);
+            if (true) { // Folia end - region threading
                 actualTargets.add(entityplayer);
             }
             // Paper end - Add PlayerSetSpawnEvent
diff --git a/src/main/java/net/minecraft/server/commands/SummonCommand.java b/src/main/java/net/minecraft/server/commands/SummonCommand.java
index e2b44b8ddb8afc6e1f7dddadb434c2268f284809..c2980f5bd826e3fb91fd19b3b0889034f3389976 100644
--- a/src/main/java/net/minecraft/server/commands/SummonCommand.java
+++ b/src/main/java/net/minecraft/server/commands/SummonCommand.java
@@ -64,11 +64,18 @@ public class SummonCommand {
             if (entity == null) {
                 throw SummonCommand.ERROR_FAILED.create();
             } else {
-                if (initialize && entity instanceof Mob) {
-                    ((Mob) entity).finalizeSpawn(source.getLevel(), source.getLevel().getCurrentDifficultyAt(entity.blockPosition()), MobSpawnType.COMMAND, (SpawnGroupData) null, (CompoundTag) null);
-                }
+                // Folia start - region threading
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                    worldserver, entity.chunkPosition().x, entity.chunkPosition().z, () -> {
+                        if (initialize && entity instanceof Mob) {
+                            ((Mob) entity).finalizeSpawn(source.getLevel(), source.getLevel().getCurrentDifficultyAt(entity.blockPosition()), MobSpawnType.COMMAND, (SpawnGroupData) null, (CompoundTag) null);
+                        }
+                        worldserver.tryAddFreshEntityWithPassengers(entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.COMMAND);
+                    }
+                );
+                // Folia end - region threading
 
-                if (!worldserver.tryAddFreshEntityWithPassengers(entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.COMMAND)) { // CraftBukkit - pass a spawn reason of "COMMAND"
+                if (false) { // CraftBukkit - pass a spawn reason of "COMMAND" // Folia - region threading
                     throw SummonCommand.ERROR_DUPLICATE_UUID.create();
                 } else {
                     return entity;
diff --git a/src/main/java/net/minecraft/server/commands/TeleportCommand.java b/src/main/java/net/minecraft/server/commands/TeleportCommand.java
index 2ddd033e1c3a2e5c8950b93c838491923803ccce..2450885ef59ad32fbfadfe03f95f9ba24b8a6886 100644
--- a/src/main/java/net/minecraft/server/commands/TeleportCommand.java
+++ b/src/main/java/net/minecraft/server/commands/TeleportCommand.java
@@ -77,7 +77,7 @@ public class TeleportCommand {
         while (iterator.hasNext()) {
             Entity entity1 = (Entity) iterator.next();
 
-            TeleportCommand.performTeleport(source, entity1, (ServerLevel) destination.level(), destination.getX(), destination.getY(), destination.getZ(), EnumSet.noneOf(RelativeMovement.class), destination.getYRot(), destination.getXRot(), (TeleportCommand.LookAt) null);
+            io.papermc.paper.threadedregions.TeleportUtils.teleport(entity1, false, destination, Float.valueOf(destination.getYRot()), Float.valueOf(destination.getXRot()), Entity.TELEPORT_FLAG_LOAD_CHUNK, org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.COMMAND, null); // Folia - region threading
         }
 
         if (targets.size() == 1) {
@@ -161,6 +161,24 @@ public class TeleportCommand {
             float f2 = Mth.wrapDegrees(yaw);
             float f3 = Mth.wrapDegrees(pitch);
 
+            // Folia start - region threading
+            if (true) {
+                ServerLevel worldFinal = world;
+                Vec3 posFinal = new Vec3(x, y, z);
+                Float yawFinal = Float.valueOf(f2);
+                Float pitchFinal = Float.valueOf(f3);
+                target.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> {
+                    nmsEntity.unRide();
+                    nmsEntity.teleportAsync(
+                        worldFinal, posFinal, yawFinal, pitchFinal, Vec3.ZERO,
+                        org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.COMMAND,
+                        Entity.TELEPORT_FLAG_LOAD_CHUNK,
+                        null
+                    );
+                }, null, 1L);
+                return;
+            }
+            // Folia end - region threading
             // CraftBukkit start - Teleport event
             boolean result;
             if (target instanceof ServerPlayer player) {
diff --git a/src/main/java/net/minecraft/server/commands/TimeCommand.java b/src/main/java/net/minecraft/server/commands/TimeCommand.java
index 44fcd43a466fb47d31ab05e44bafbef3c4cae63f..2989750a75b3dd244cf8f9ca78769308f982374b 100644
--- a/src/main/java/net/minecraft/server/commands/TimeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/TimeCommand.java
@@ -58,6 +58,7 @@ public class TimeCommand {
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
 
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
             // CraftBukkit start
             TimeSkipEvent event = new TimeSkipEvent(worldserver.getWorld(), TimeSkipEvent.SkipReason.COMMAND, time - worldserver.getDayTime());
             Bukkit.getPluginManager().callEvent(event);
@@ -65,6 +66,7 @@ public class TimeCommand {
                 worldserver.setDayTime((long) worldserver.getDayTime() + event.getSkipAmount());
             }
             // CraftBukkit end
+            }); // Folia - region threading
         }
 
         source.sendSuccess(() -> {
@@ -79,6 +81,7 @@ public class TimeCommand {
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
 
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
             // CraftBukkit start
             TimeSkipEvent event = new TimeSkipEvent(worldserver.getWorld(), TimeSkipEvent.SkipReason.COMMAND, time);
             Bukkit.getPluginManager().callEvent(event);
@@ -86,13 +89,16 @@ public class TimeCommand {
                 worldserver.setDayTime(worldserver.getDayTime() + event.getSkipAmount());
             }
             // CraftBukkit end
+            }); // Folia - region threading
         }
 
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         int j = TimeCommand.getDayTime(source.getLevel());
 
         source.sendSuccess(() -> {
             return Component.translatable("commands.time.set", j);
         }, true);
-        return j;
+        }); // Folia - region threading
+        return 0; // Folia - region threading
     }
 }
diff --git a/src/main/java/net/minecraft/server/commands/WeatherCommand.java b/src/main/java/net/minecraft/server/commands/WeatherCommand.java
index 3100dcd0bbba9e109c26f5932c648cd2bab212d7..e17fcbe35cb7293ac72d49c1fa659e70dc0b38ff 100644
--- a/src/main/java/net/minecraft/server/commands/WeatherCommand.java
+++ b/src/main/java/net/minecraft/server/commands/WeatherCommand.java
@@ -48,20 +48,26 @@ public class WeatherCommand {
     }
 
     private static int setClear(CommandSourceStack source, int duration) {
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         source.getLevel().setWeatherParameters(getDuration(source, duration, ServerLevel.RAIN_DELAY), 0, false, false);
         source.sendSuccess(() -> Component.translatable("commands.weather.set.clear"), true);
+        }); // Folia - region threading
         return duration;
     }
 
     private static int setRain(CommandSourceStack source, int duration) {
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         source.getLevel().setWeatherParameters(0, getDuration(source, duration, ServerLevel.RAIN_DURATION), true, false);
         source.sendSuccess(() -> Component.translatable("commands.weather.set.rain"), true);
+        }); // Folia - region threading
         return duration;
     }
 
     private static int setThunder(CommandSourceStack source, int duration) {
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
         source.getLevel().setWeatherParameters(0, getDuration(source, duration, ServerLevel.THUNDER_DURATION), true, true);
         source.sendSuccess(() -> Component.translatable("commands.weather.set.thunder"), true);
+        }); // Folia - region threading
         return duration;
     }
 }
diff --git a/src/main/java/net/minecraft/server/commands/WorldBorderCommand.java b/src/main/java/net/minecraft/server/commands/WorldBorderCommand.java
index 812f2adc6fc20aa126e629284fe594a923b24540..0a5e6961fb37e9a53cd39b1bd233e0204986b244 100644
--- a/src/main/java/net/minecraft/server/commands/WorldBorderCommand.java
+++ b/src/main/java/net/minecraft/server/commands/WorldBorderCommand.java
@@ -56,7 +56,17 @@ public class WorldBorderCommand {
         })))));
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int setDamageBuffer(CommandSourceStack source, float distance) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+                // Folia end - region threading
         WorldBorder worldborder = source.getLevel().getWorldBorder(); // CraftBukkit
 
         if (worldborder.getDamageSafeZone() == (double) distance) {
@@ -66,11 +76,22 @@ public class WorldBorderCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.worldborder.damage.buffer.success", String.format(Locale.ROOT, "%.2f", distance));
             }, true);
-            return (int) distance;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int setDamageAmount(CommandSourceStack source, float damagePerBlock) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+                // Folia end - region threading
         WorldBorder worldborder = source.getLevel().getWorldBorder(); // CraftBukkit
 
         if (worldborder.getDamagePerBlock() == (double) damagePerBlock) {
@@ -80,11 +101,22 @@ public class WorldBorderCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.worldborder.damage.amount.success", String.format(Locale.ROOT, "%.2f", damagePerBlock));
             }, true);
-            return (int) damagePerBlock;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int setWarningTime(CommandSourceStack source, int time) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+                // Folia end - region threading
         WorldBorder worldborder = source.getLevel().getWorldBorder(); // CraftBukkit
 
         if (worldborder.getWarningTime() == time) {
@@ -94,11 +126,22 @@ public class WorldBorderCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.worldborder.warning.time.success", time);
             }, true);
-            return time;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int setWarningDistance(CommandSourceStack source, int distance) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+                // Folia end - region threading
         WorldBorder worldborder = source.getLevel().getWorldBorder(); // CraftBukkit
 
         if (worldborder.getWarningBlocks() == distance) {
@@ -108,20 +151,38 @@ public class WorldBorderCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.worldborder.warning.distance.success", distance);
             }, true);
-            return distance;
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int getSize(CommandSourceStack source) {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+                // Folia end - region threading
         double d0 = source.getLevel().getWorldBorder().getSize(); // CraftBukkit
 
         source.sendSuccess(() -> {
             return Component.translatable("commands.worldborder.get", String.format(Locale.ROOT, "%.0f", d0));
         }, false);
-        return Mth.floor(d0 + 0.5D);
+        return; // Folia - region threading
+        // Folia start - region threading
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int setCenter(CommandSourceStack source, Vec2 pos) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+                // Folia end - region threading
         WorldBorder worldborder = source.getLevel().getWorldBorder(); // CraftBukkit
 
         if (worldborder.getCenterX() == (double) pos.x && worldborder.getCenterZ() == (double) pos.y) {
@@ -131,13 +192,24 @@ public class WorldBorderCommand {
             source.sendSuccess(() -> {
                 return Component.translatable("commands.worldborder.center.success", String.format(Locale.ROOT, "%.2f", pos.x), String.format(Locale.ROOT, "%.2f", pos.y));
             }, true);
-            return 0;
+            return; // Folia - region threading
         } else {
             throw WorldBorderCommand.ERROR_TOO_FAR_OUT.create();
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int setSize(CommandSourceStack source, double distance, long time) throws CommandSyntaxException {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+            try {
+                // Folia end - region threading
         WorldBorder worldborder = source.getLevel().getWorldBorder(); // CraftBukkit
         double d1 = worldborder.getSize();
 
@@ -166,7 +238,14 @@ public class WorldBorderCommand {
                 }, true);
             }
 
-            return (int) (distance - d1);
+            return; // Folia - region threading
         }
+        // Folia start - region threading
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 }
diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index 68d268b6fff126e8645b6deec3fb549ea2286b77..6b3242117d62175de462d04e4d178b49ae2521e9 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -443,9 +443,9 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
     }
 
     @Override
-    public void tickChildren(BooleanSupplier shouldKeepTicking) {
-        super.tickChildren(shouldKeepTicking);
-        this.handleConsoleInputs();
+    public void tickChildren(BooleanSupplier shouldKeepTicking, io.papermc.paper.threadedregions.TickRegions.TickRegionData region) { // Folia - region threading
+        super.tickChildren(shouldKeepTicking, region); // Folia - region threading
+        if (region == null) this.handleConsoleInputs(); // Folia - region threading
     }
 
     @Override
@@ -767,7 +767,7 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
         Waitable[] waitableArray = new Waitable[1]; // Paper
         rconConsoleSource.prepareForCommand();
         final java.util.concurrent.atomic.AtomicReference<String> command = new java.util.concurrent.atomic.AtomicReference<>(s); // Paper
-        this.executeBlocking(() -> {
+        Runnable sync = () -> { // Folia - region threading
             CommandSourceStack wrapper = rconConsoleSource.createCommandSourceStack();
             RemoteServerCommandEvent event = new RemoteServerCommandEvent(rconConsoleSource.getBukkitSender(wrapper), s);
             this.server.getPluginManager().callEvent(event);
@@ -791,7 +791,16 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
             ConsoleInput serverCommand = new ConsoleInput(event.getCommand(), wrapper);
             this.server.dispatchServerCommand(event.getSender(), serverCommand);
             } // Paper
-        });
+        }; // Folia start - region threading
+        java.util.concurrent.CompletableFuture
+            .runAsync(sync, io.papermc.paper.threadedregions.RegionizedServer.getInstance()::addTask)
+            .whenComplete((Void r, Throwable t) -> {
+                if (t != null) {
+                    LOGGER.error("Error handling command for rcon: " + s, t);
+                }
+            })
+            .join();
+        // Folia end - region threading
         // Paper start
         if (waitableArray[0] != null) {
             //noinspection unchecked
diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index 627a88ec8c3b215b19b55a6d461c8754b4fcd1e8..4e8b325cad5ef1a59ac3ba725d3de6e43d0fd5d6 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -81,7 +81,7 @@ public class ChunkHolder {
     public void onChunkAdd() {
         // Paper start - optimise chunk tick iteration
         if (this.needsBroadcastChanges()) {
-            this.chunkMap.needsChangeBroadcasting.add(this);
+            this.chunkMap.level.needsChangeBroadcasting.add(this); // Folia - region threading
         }
         // Paper end - optimise chunk tick iteration
     }
@@ -89,7 +89,7 @@ public class ChunkHolder {
     public void onChunkRemove() {
         // Paper start - optimise chunk tick iteration
         if (this.needsBroadcastChanges()) {
-            this.chunkMap.needsChangeBroadcasting.remove(this);
+            this.chunkMap.level.needsChangeBroadcasting.remove(this); // Folia - region threading
         }
         // Paper end - optimise chunk tick iteration
     }
@@ -284,7 +284,7 @@ public class ChunkHolder {
 
     private void addToBroadcastMap() {
         io.papermc.paper.util.TickThread.ensureTickThread(this.chunkMap.level, this.pos, "Asynchronous ChunkHolder update is not allowed");
-        this.chunkMap.needsChangeBroadcasting.add(this);
+        this.chunkMap.level.needsChangeBroadcasting.add(this); // Folia - region threading
     }
     // Paper end - optimise chunk tick iteration
 
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 12109446fc76a39faee6cda042ca48b3fd3809f4..d45f4efd66380ace44fb0aa3f8a2569dc702e1aa 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -137,77 +137,41 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     private final AtomicInteger tickingGenerated;
     public final StructureTemplateManager structureTemplateManager; // Paper - rewrite chunk system
     private final String storageName;
-    private final PlayerMap playerMap;
-    public final Int2ObjectMap<ChunkMap.TrackedEntity> entityMap;
+    //private final PlayerMap playerMap; // Folia - region threading
+    //public final Int2ObjectMap<ChunkMap.TrackedEntity> entityMap; // Folia - region threading
     private final Long2ByteMap chunkTypeCache;
     private final Long2LongMap chunkSaveCooldowns;
     private final Queue<Runnable> unloadQueue;
     public int serverViewDistance;
 
     // Paper start - distance maps
-    private final com.destroystokyo.paper.util.misc.PooledLinkedHashSets<ServerPlayer> pooledLinkedPlayerHashSets = new com.destroystokyo.paper.util.misc.PooledLinkedHashSets<>();
-    // Paper start - use distance map to optimise tracker
-    public static boolean isLegacyTrackingEntity(Entity entity) {
-        return entity.isLegacyTrackingEntity;
-    }
-
-    // inlined EnumMap, TrackingRange.TrackingRangeType
-    static final org.spigotmc.TrackingRange.TrackingRangeType[] TRACKING_RANGE_TYPES = org.spigotmc.TrackingRange.TrackingRangeType.values();
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap[] playerEntityTrackerTrackMaps;
-    final int[] entityTrackerTrackRanges;
-    public final int getEntityTrackerRange(final int ordinal) {
-        return this.entityTrackerTrackRanges[ordinal];
-    }
-
-    private int convertSpigotRangeToVanilla(final int vanilla) {
-        return net.minecraft.server.MinecraftServer.getServer().getScaledTrackingDistance(vanilla);
-    }
-    // Paper end - use distance map to optimise tracker
+    // Folia - region threading
 
     void addPlayerToDistanceMaps(ServerPlayer player) {
         int chunkX = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getX());
         int chunkZ = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getZ());
         // Note: players need to be explicitly added to distance maps before they can be updated
-        this.nearbyPlayers.addPlayer(player);
+        // Folia - region threading
         this.level.playerChunkLoader.addPlayer(player); // Paper - replace chunk loader
-        // Paper start - use distance map to optimise entity tracker
-        for (int i = 0, len = TRACKING_RANGE_TYPES.length; i < len; ++i) {
-            com.destroystokyo.paper.util.misc.PlayerAreaMap trackMap = this.playerEntityTrackerTrackMaps[i];
-            int trackRange = this.entityTrackerTrackRanges[i];
-
-            trackMap.add(player, chunkX, chunkZ, Math.min(trackRange, io.papermc.paper.chunk.system.ChunkSystem.getSendViewDistance(player)));
-        }
-        // Paper end - use distance map to optimise entity tracker
+        // Folia - region threading
     }
 
     void removePlayerFromDistanceMaps(ServerPlayer player) {
         int chunkX = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getX());
         int chunkZ = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getZ());
         // Note: players need to be explicitly added to distance maps before they can be updated
-        this.nearbyPlayers.removePlayer(player);
+        // Folia - region threading
         this.level.playerChunkLoader.removePlayer(player); // Paper - replace chunk loader
-        // Paper start - use distance map to optimise tracker
-        for (int i = 0, len = TRACKING_RANGE_TYPES.length; i < len; ++i) {
-            this.playerEntityTrackerTrackMaps[i].remove(player);
-        }
-        // Paper end - use distance map to optimise tracker
-        this.playerMobSpawnMap.remove(player); // Paper - optimise chunk tick iteration
+        // Folia - region threading
     }
 
     void updateMaps(ServerPlayer player) {
         int chunkX = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getX());
         int chunkZ = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getZ());
         // Note: players need to be explicitly added to distance maps before they can be updated
-        this.nearbyPlayers.tickPlayer(player);
+        // Folia - region threading
         this.level.playerChunkLoader.updatePlayer(player); // Paper - replace chunk loader
-        // Paper start - use distance map to optimise entity tracker
-        for (int i = 0, len = TRACKING_RANGE_TYPES.length; i < len; ++i) {
-            com.destroystokyo.paper.util.misc.PlayerAreaMap trackMap = this.playerEntityTrackerTrackMaps[i];
-            int trackRange = this.entityTrackerTrackRanges[i];
-
-            trackMap.update(player, chunkX, chunkZ, Math.min(trackRange, io.papermc.paper.chunk.system.ChunkSystem.getSendViewDistance(player)));
-        }
-        // Paper end - use distance map to optimise entity tracker
+        // Folia - region threading
     }
     // Paper end
     // Paper start
@@ -239,19 +203,19 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     public final ChunkHolder getUnloadingChunkHolder(int chunkX, int chunkZ) {
         return null; // Paper - rewrite chunk system
     }
-    public final io.papermc.paper.util.player.NearbyPlayers nearbyPlayers;
+    //public final io.papermc.paper.util.player.NearbyPlayers nearbyPlayers; // Folia - region threading
     // Paper end
     // Paper start - optimise chunk tick iteration
-    public final it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>();
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobSpawnMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets);
+    //public final it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>(); // Folia - region threading
+    //public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobSpawnMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets); // Folia - region threading
     // Paper end - optimise chunk tick iteration
 
     public ChunkMap(ServerLevel world, LevelStorageSource.LevelStorageAccess session, DataFixer dataFixer, StructureTemplateManager structureTemplateManager, Executor executor, BlockableEventLoop<Runnable> mainThreadExecutor, LightChunkGetter chunkProvider, ChunkGenerator chunkGenerator, ChunkProgressListener worldGenerationProgressListener, ChunkStatusUpdateListener chunkStatusChangeListener, Supplier<DimensionDataStorage> persistentStateManagerFactory, int viewDistance, boolean dsync) {
         super(session.getDimensionPath(world.dimension()).resolve("region"), dataFixer, dsync);
         // Paper - rewrite chunk system
         this.tickingGenerated = new AtomicInteger();
-        this.playerMap = new PlayerMap();
-        this.entityMap = new Int2ObjectOpenHashMap();
+        //this.playerMap = new PlayerMap(); // Folia - region threading
+        //this.entityMap = new Int2ObjectOpenHashMap(); // Folia - region threading
         this.chunkTypeCache = new Long2ByteOpenHashMap();
         this.chunkSaveCooldowns = new Long2LongOpenHashMap();
         this.unloadQueue = Queues.newConcurrentLinkedQueue();
@@ -296,57 +260,18 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.setServerViewDistance(viewDistance);
         // Paper start
         this.dataRegionManager = new io.papermc.paper.chunk.SingleThreadChunkRegionManager(this.level, 2, (1.0 / 3.0), 1, 6, "Data", DataRegionData::new, DataRegionSectionData::new);
-        this.regionManagers.add(this.dataRegionManager);
-        this.nearbyPlayers = new io.papermc.paper.util.player.NearbyPlayers(this.level);
+        //this.regionManagers.add(this.dataRegionManager); // Folia - region threading
+        //this.nearbyPlayers = new io.papermc.paper.util.player.NearbyPlayers(this.level); // Folia - region threading
         // Paper end
         // Paper start - use distance map to optimise entity tracker
-        this.playerEntityTrackerTrackMaps = new com.destroystokyo.paper.util.misc.PlayerAreaMap[TRACKING_RANGE_TYPES.length];
-        this.entityTrackerTrackRanges = new int[TRACKING_RANGE_TYPES.length];
-
-        org.spigotmc.SpigotWorldConfig spigotWorldConfig = this.level.spigotConfig;
-
-        for (int ordinal = 0, len = TRACKING_RANGE_TYPES.length; ordinal < len; ++ordinal) {
-            org.spigotmc.TrackingRange.TrackingRangeType trackingRangeType = TRACKING_RANGE_TYPES[ordinal];
-            int configuredSpigotValue;
-            switch (trackingRangeType) {
-                case PLAYER:
-                    configuredSpigotValue = spigotWorldConfig.playerTrackingRange;
-                    break;
-                case ANIMAL:
-                    configuredSpigotValue = spigotWorldConfig.animalTrackingRange;
-                    break;
-                case MONSTER:
-                    configuredSpigotValue = spigotWorldConfig.monsterTrackingRange;
-                    break;
-                case MISC:
-                    configuredSpigotValue = spigotWorldConfig.miscTrackingRange;
-                    break;
-                case OTHER:
-                    configuredSpigotValue = spigotWorldConfig.otherTrackingRange;
-                    break;
-                case ENDERDRAGON:
-                    configuredSpigotValue = EntityType.ENDER_DRAGON.clientTrackingRange() * 16;
-                    break;
-                case DISPLAY:
-                    configuredSpigotValue = spigotWorldConfig.displayTrackingRange;
-                    break;
-                default:
-                    throw new IllegalStateException("Missing case for enum " + trackingRangeType);
-            }
-            configuredSpigotValue = convertSpigotRangeToVanilla(configuredSpigotValue);
-
-            int trackRange = (configuredSpigotValue >>> 4) + ((configuredSpigotValue & 15) != 0 ? 1 : 0);
-            this.entityTrackerTrackRanges[ordinal] = trackRange;
-
-            this.playerEntityTrackerTrackMaps[ordinal] = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets);
-        }
+        // Folia - region threading
         // Paper end - use distance map to optimise entity tracker
     }
 
     // Paper start
     // always use accessor, so folia can override
     public final io.papermc.paper.util.player.NearbyPlayers getNearbyPlayers() {
-        return this.nearbyPlayers;
+        return this.level.getCurrentWorldData().getNearbyPlayers(); // Folia - region threading
     }
     // Paper end
 
@@ -667,6 +592,12 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     // Paper start - duplicate uuid resolving
     // rets true if to prevent the entity from being added
     public static boolean checkDupeUUID(ServerLevel level, Entity entity) {
+        // Folia start - region threading
+        if (true) {
+            // TODO fix this shit later
+            return false;
+        }
+        // Folia end - region threading
         io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode mode = level.paperConfig().entities.spawning.duplicateUuid.mode;
         if (mode != io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode.WARN
             && mode != io.papermc.paper.configuration.WorldConfiguration.Entities.Spawning.DuplicateUUID.DuplicateUUIDMode.DELETE
@@ -913,6 +844,38 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     boolean anyPlayerCloseEnoughForSpawning(ChunkPos chunkcoordintpair, boolean reducedRange) {
+        // Folia start - region threading
+        if (true) {
+            java.util.List<ServerPlayer> players = this.level.getLocalPlayers();
+            if (reducedRange) {
+                for (int i = 0, len = players.size(); i < len; ++i) {
+                    ServerPlayer player = players.get(i);
+                    if (!player.affectsSpawning || player.isSpectator()) {
+                        continue;
+                    }
+                    // don't check spectator and whatnot, already handled by mob spawn map update
+                    if (euclideanDistanceSquared(chunkcoordintpair, player) < player.lastEntitySpawnRadiusSquared) {
+                        return true; // in range
+                    }
+                }
+            } else {
+                final double range = (DistanceManager.MOB_SPAWN_RANGE * 16) * (DistanceManager.MOB_SPAWN_RANGE * 16);
+                // before spigot, mob spawn range was actually mob spawn range + tick range, but it was split
+                for (int i = 0, len = players.size(); i < len; ++i) {
+                    ServerPlayer player = players.get(i);
+                    if (!player.affectsSpawning || player.isSpectator()) {
+                        continue;
+                    }
+                    // don't check spectator and whatnot, already handled by mob spawn map update
+                    if (euclideanDistanceSquared(chunkcoordintpair, player) < range) {
+                        return true; // in range
+                    }
+                }
+            }
+            // no players in range
+            return false;
+        }
+        // Folia end - region threading
         int chunkRange = this.level.spigotConfig.mobSpawnRange;
         chunkRange = (chunkRange > this.level.spigotConfig.viewDistance) ? (byte) this.level.spigotConfig.viewDistance : chunkRange;
         chunkRange = (chunkRange > 8) ? 8 : chunkRange;
@@ -924,7 +887,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         if (!this.distanceManager.hasPlayersNearby(chunkcoordintpair.toLong())) {
             return false;
         } else {
-            Iterator iterator = this.playerMap.getAllPlayers().iterator();
+            Iterator iterator = null; // Folia - region threading
 
             ServerPlayer entityplayer;
 
@@ -956,7 +919,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             return List.of();
         } else {
             Builder<ServerPlayer> builder = ImmutableList.builder();
-            Iterator iterator = this.playerMap.getAllPlayers().iterator();
+            Iterator iterator = this.level.getLocalPlayers().iterator(); // Folia - region threading
 
             while (iterator.hasNext()) {
                 ServerPlayer entityplayer = (ServerPlayer) iterator.next();
@@ -985,25 +948,19 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     void updatePlayerStatus(ServerPlayer player, boolean added) {
-        boolean flag1 = this.skipPlayer(player);
-        boolean flag2 = this.playerMap.ignoredOrUnknown(player);
+        // Folia - region threading
 
         if (added) {
-            this.playerMap.addPlayer(player, flag1);
+            // Folia - region threading
             this.updatePlayerPos(player);
-            if (!flag1) {
-                this.distanceManager.addPlayer(SectionPos.of((EntityAccess) player), player);
-            }
+            // Folia - region threading
 
             // Paper - handled by player chunk loader
             this.addPlayerToDistanceMaps(player); // Paper - distance maps
         } else {
             SectionPos sectionposition = player.getLastSectionPos();
 
-            this.playerMap.removePlayer(player);
-            if (!flag2) {
-                this.distanceManager.removePlayer(sectionposition, player);
-            }
+            // Folia - region threading
 
             this.removePlayerFromDistanceMaps(player); // Paper - distance maps
             // Paper - handled by player chunk loader
@@ -1018,31 +975,13 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     public void move(ServerPlayer player) {
-        // Paper - delay this logic for the entity tracker tick, no need to duplicate it
+        // Folia - region threading - entity tracker optimisations
 
-        SectionPos sectionposition = player.getLastSectionPos();
-        SectionPos sectionposition1 = SectionPos.of((EntityAccess) player);
-        boolean flag = this.playerMap.ignored(player);
-        boolean flag1 = this.skipPlayer(player);
-        boolean flag2 = sectionposition.asLong() != sectionposition1.asLong();
+        // Folia - region threading
 
-        if (flag2 || flag != flag1) {
+        if (true) { // Folia - region threading
             this.updatePlayerPos(player);
-            if (!flag) {
-                this.distanceManager.removePlayer(sectionposition, player);
-            }
-
-            if (!flag1) {
-                this.distanceManager.addPlayer(sectionposition1, player);
-            }
-
-            if (!flag && flag1) {
-                this.playerMap.ignorePlayer(player);
-            }
-
-            if (flag && !flag1) {
-                this.playerMap.unIgnorePlayer(player);
-            }
+            // Folia - region threading
 
             // Paper - replaced by PlayerChunkLoader
         }
@@ -1073,9 +1012,9 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     public void addEntity(Entity entity) {
         org.spigotmc.AsyncCatcher.catchOp("entity track"); // Spigot
         // Paper start - ignore and warn about illegal addEntity calls instead of crashing server
-        if (!entity.valid || entity.level() != this.level || this.entityMap.containsKey(entity.getId())) {
+        if (!entity.valid || entity.level() != this.level || entity.tracker != null) { // Folia - region threading
             LOGGER.error("Illegal ChunkMap::addEntity for world " + this.level.getWorld().getName()
-                + ": " + entity  + (this.entityMap.containsKey(entity.getId()) ? " ALREADY CONTAINED (This would have crashed your server)" : ""), new Throwable());
+                + ": " + entity  + (entity.tracker != null ? " ALREADY CONTAINED (This would have crashed your server)" : ""), new Throwable());
             return;
         }
         // Paper end - ignore and warn about illegal addEntity calls instead of crashing server
@@ -1088,27 +1027,25 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             if (i != 0) {
                 int j = entitytypes.updateInterval();
 
-                if (this.entityMap.containsKey(entity.getId())) {
+                if (entity.tracker != null) { // Folia - region threading
                     throw (IllegalStateException) Util.pauseInIde(new IllegalStateException("Entity is already tracked!"));
                 } else {
                     ChunkMap.TrackedEntity playerchunkmap_entitytracker = new ChunkMap.TrackedEntity(entity, i, j, entitytypes.trackDeltas());
 
                     entity.tracker = playerchunkmap_entitytracker; // Paper - Fast access to tracker
-                    this.entityMap.put(entity.getId(), playerchunkmap_entitytracker);
-                    playerchunkmap_entitytracker.updatePlayers(entity.getPlayersInTrackRange()); // Paper - don't search all players
+                    // Folia - region threading
+                    playerchunkmap_entitytracker.updatePlayers(this.level.getLocalPlayers()); // Folia - region threading
                     if (entity instanceof ServerPlayer) {
                         ServerPlayer entityplayer = (ServerPlayer) entity;
 
                         this.updatePlayerStatus(entityplayer, true);
-                        ObjectIterator objectiterator = this.entityMap.values().iterator();
-
-                        while (objectiterator.hasNext()) {
-                            ChunkMap.TrackedEntity playerchunkmap_entitytracker1 = (ChunkMap.TrackedEntity) objectiterator.next();
-
-                            if (playerchunkmap_entitytracker1.entity != entityplayer) {
-                                playerchunkmap_entitytracker1.updatePlayer(entityplayer);
+                        // Folia start - region threading
+                        for (Entity possible : this.level.getCurrentWorldData().getLoadedEntities()) {
+                            if (possible.tracker != null) {
+                                possible.tracker.updatePlayer(entityplayer);
                             }
                         }
+                        // Folia end - region threading
                     }
 
                 }
@@ -1122,16 +1059,16 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             ServerPlayer entityplayer = (ServerPlayer) entity;
 
             this.updatePlayerStatus(entityplayer, false);
-            ObjectIterator objectiterator = this.entityMap.values().iterator();
-
-            while (objectiterator.hasNext()) {
-                ChunkMap.TrackedEntity playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) objectiterator.next();
-
-                playerchunkmap_entitytracker.removePlayer(entityplayer);
+            // Folia start - region threading
+            for (Entity possible : this.level.getCurrentWorldData().getLocalEntities()) {
+                if (possible.tracker != null) {
+                    possible.tracker.removePlayer(entityplayer);
+                }
             }
+            // Folia end - region threading
         }
 
-        ChunkMap.TrackedEntity playerchunkmap_entitytracker1 = (ChunkMap.TrackedEntity) this.entityMap.remove(entity.getId());
+        ChunkMap.TrackedEntity playerchunkmap_entitytracker1 = entity.tracker; // Folia - region threading
 
         if (playerchunkmap_entitytracker1 != null) {
             playerchunkmap_entitytracker1.broadcastRemoved();
@@ -1139,82 +1076,37 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         entity.tracker = null; // Paper - We're no longer tracked
     }
 
-    // Paper start - optimised tracker
-    private final void processTrackQueue() {
-        this.level.timings.tracker1.startTiming();
-        try {
-            for (TrackedEntity tracker : this.entityMap.values()) {
-                // update tracker entry
-                tracker.updatePlayers(tracker.entity.getPlayersInTrackRange());
+    // Folia start - region threading - replace entity tracking ticking
+    private void foliaEntityTrackerTick() {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.level.getCurrentWorldData();
+        io.papermc.paper.util.player.NearbyPlayers nearbyPlayers = worldData.getNearbyPlayers();
+        for (Entity entity : worldData.getLoadedEntities()) {
+            TrackedEntity tracker = entity.tracker;
+            if (tracker == null) {
+                continue;
             }
-        } finally {
-            this.level.timings.tracker1.stopTiming();
-        }
-
-
-        this.level.timings.tracker2.startTiming();
-        try {
-            for (TrackedEntity tracker : this.entityMap.values()) {
-                tracker.serverEntity.sendChanges();
+            tracker.tick(nearbyPlayers.getChunk(entity.chunkPosition()));
+            tracker.serverEntity.sendChanges();
+        }
+        // process unloads
+        for (Entity entity : worldData.takeTrackingUnloads()) {
+            TrackedEntity tracker = entity.tracker;
+            if (tracker == null) {
+                continue;
             }
-        } finally {
-            this.level.timings.tracker2.stopTiming();
+            tracker.clearPlayers();
         }
     }
-    // Paper end - optimised tracker
+    // Folia end - region threading - replace entity tracking ticking
 
-    protected void tick() {
-        // Paper start - optimized tracker
-        if (true) {
-            this.processTrackQueue();
-            return;
-        }
-        // Paper end - optimized tracker
-        List<ServerPlayer> list = Lists.newArrayList();
-        List<ServerPlayer> list1 = this.level.players();
-        ObjectIterator objectiterator = this.entityMap.values().iterator();
-        level.timings.tracker1.startTiming(); // Paper
-
-        ChunkMap.TrackedEntity playerchunkmap_entitytracker;
-
-        while (objectiterator.hasNext()) {
-            playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) objectiterator.next();
-            SectionPos sectionposition = playerchunkmap_entitytracker.lastSectionPos;
-            SectionPos sectionposition1 = SectionPos.of((EntityAccess) playerchunkmap_entitytracker.entity);
-            boolean flag = !Objects.equals(sectionposition, sectionposition1);
-
-            if (flag) {
-                playerchunkmap_entitytracker.updatePlayers(list1);
-                Entity entity = playerchunkmap_entitytracker.entity;
-
-                if (entity instanceof ServerPlayer) {
-                    list.add((ServerPlayer) entity);
-                }
-
-                playerchunkmap_entitytracker.lastSectionPos = sectionposition1;
-            }
-
-            if (flag || this.distanceManager.inEntityTickingRange(sectionposition1.chunk().toLong())) {
-                playerchunkmap_entitytracker.serverEntity.sendChanges();
-            }
-        }
-        level.timings.tracker1.stopTiming(); // Paper
-
-        if (!list.isEmpty()) {
-            objectiterator = this.entityMap.values().iterator();
-
-            level.timings.tracker2.startTiming(); // Paper
-            while (objectiterator.hasNext()) {
-                playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) objectiterator.next();
-                playerchunkmap_entitytracker.updatePlayers(list);
-            }
-            level.timings.tracker2.stopTiming(); // Paper
-        }
+    // Folia - region threading - replace entity tracking ticking
 
+    protected void tick() {
+        this.foliaEntityTrackerTick(); // Folia - region threading - replace entity tracking ticking
     }
 
     public void broadcast(Entity entity, Packet<?> packet) {
-        ChunkMap.TrackedEntity playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) this.entityMap.get(entity.getId());
+        ChunkMap.TrackedEntity playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) entity.tracker; // Folia - region threading
 
         if (playerchunkmap_entitytracker != null) {
             playerchunkmap_entitytracker.broadcast(packet);
@@ -1223,7 +1115,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     protected void broadcastAndSend(Entity entity, Packet<?> packet) {
-        ChunkMap.TrackedEntity playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) this.entityMap.get(entity.getId());
+        ChunkMap.TrackedEntity playerchunkmap_entitytracker = (ChunkMap.TrackedEntity) entity.tracker; // Folia - region threading
 
         if (playerchunkmap_entitytracker != null) {
             playerchunkmap_entitytracker.broadcastAndSend(packet);
@@ -1400,6 +1292,78 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             }
 
         }
+        // Folia start - region threading
+        private int lastChunkUpdate = -1;
+        private io.papermc.paper.util.player.NearbyPlayers.TrackedChunk lastTrackedChunk;
+        public void tick(io.papermc.paper.util.player.NearbyPlayers.TrackedChunk chunk) {
+            if (chunk == null) {
+                this.clearPlayers();
+                return;
+            }
+
+            com.destroystokyo.paper.util.maplist.ReferenceList<ServerPlayer> players =
+                chunk.getPlayers(io.papermc.paper.util.player.NearbyPlayers.NearbyMapType.VIEW_DISTANCE);
+
+            if (players == null) {
+                this.clearPlayers();
+                return;
+            }
+
+            int lastChunkUpdate = this.lastChunkUpdate;
+            int currChunkUpdate = chunk.getUpdateCount();
+            io.papermc.paper.util.player.NearbyPlayers.TrackedChunk lastTrackedChunk = this.lastTrackedChunk;
+            this.lastChunkUpdate = currChunkUpdate;
+            this.lastTrackedChunk = chunk;
+
+            for (int i = 0, len = players.size(); i < len; ++i) {
+                ServerPlayer player = players.getUnchecked(i);
+                this.updatePlayer(player);
+            }
+
+            if (lastChunkUpdate != currChunkUpdate || lastTrackedChunk != chunk) {
+                // need to purge any players possible not in the chunk list
+                for (ServerPlayerConnection conn : new java.util.ArrayList<>(this.seenBy)) {
+                    ServerPlayer player = conn.getPlayer();
+                    if (!players.contains(player)) {
+                        this.removePlayer(player);
+                    }
+                }
+            }
+        }
+
+        public void removeNonTickThreadPlayers() {
+            boolean foundToRemove = false;
+            for (ServerPlayerConnection conn : this.seenBy) {
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(conn.getPlayer())) {
+                    foundToRemove = true;
+                    break;
+                }
+            }
+
+            if (!foundToRemove) {
+                return;
+            }
+
+            for (ServerPlayerConnection conn : new java.util.ArrayList<>(this.seenBy)) {
+                ServerPlayer player = conn.getPlayer();
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(player)) {
+                    this.removePlayer(player);
+                }
+            }
+        }
+
+        public void clearPlayers() {
+            this.lastChunkUpdate = -1;
+            this.lastTrackedChunk = null;
+            if (this.seenBy.isEmpty()) {
+                return;
+            }
+            for (ServerPlayerConnection conn : new java.util.ArrayList<>(this.seenBy)) {
+                ServerPlayer player = conn.getPlayer();
+                this.removePlayer(player);
+            }
+        }
+        // Folia end - region threading
 
         public void updatePlayer(ServerPlayer player) {
             org.spigotmc.AsyncCatcher.catchOp("player tracker update"); // Spigot
@@ -1423,9 +1387,14 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                     }
                 }
                 // Paper end - Configurable entity tracking range by Y
+                // Folia start - region threading
+                if (flag && (this.entity instanceof ServerPlayer thisEntity) && thisEntity.broadcastedDeath) {
+                    flag = false;
+                }
+                // Folia end - region threading
 
                 // CraftBukkit start - respect vanish API
-                if (flag && !player.getBukkitEntity().canSee(this.entity.getBukkitEntity())) { // Paper - only consider hits
+                if (flag && (!io.papermc.paper.util.TickThread.isTickThreadFor(player) || !player.getBukkitEntity().canSee(this.entity.getBukkitEntity()))) { // Paper - only consider hits // Folia - region threading
                     flag = false;
                 }
                 // CraftBukkit end
diff --git a/src/main/java/net/minecraft/server/level/DistanceManager.java b/src/main/java/net/minecraft/server/level/DistanceManager.java
index 7c425ac50c83757b66a2178bc19d4c920b82f12f..584ee79355f1825b42bc98e508a3678b22886831 100644
--- a/src/main/java/net/minecraft/server/level/DistanceManager.java
+++ b/src/main/java/net/minecraft/server/level/DistanceManager.java
@@ -191,11 +191,11 @@ public abstract class DistanceManager {
     }
 
     public int getNaturalSpawnChunkCount() {
-        return this.chunkMap.playerMobSpawnMap.size(); // Paper - optimise chunk tick iteration
+        return this.chunkMap.level.getCurrentWorldData().mobSpawnMap.size(); // Paper - optimise chunk tick iteration // Folia - region threading
     }
 
     public boolean hasPlayersNearby(long chunkPos) {
-        return this.chunkMap.playerMobSpawnMap.getObjectsInRange(chunkPos) != null; // Paper - optimise chunk tick iteration
+        return this.chunkMap.level.getCurrentWorldData().mobSpawnMap.getObjectsInRange(chunkPos) != null; // Paper - optimise chunk tick iteration // Folia - region threading
     }
 
     public String getDebugStatus() {
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index 366c0c9b45a819f7f94ebe3e49b8ab7f9edf9ce7..d532043f33825ce2971d9e53f290cdead22d6916 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -58,23 +58,20 @@ public class ServerChunkCache extends ChunkSource {
     public final ServerChunkCache.MainThreadExecutor mainThreadProcessor;
     public final ChunkMap chunkMap;
     private final DimensionDataStorage dataStorage;
-    private long lastInhabitedUpdate;
+    //private long lastInhabitedUpdate; // Folia - region threading
     public boolean spawnEnemies = true;
     public boolean spawnFriendlies = true;
     private static final int CACHE_SIZE = 4;
     private final long[] lastChunkPos = new long[4];
     private final ChunkStatus[] lastChunkStatus = new ChunkStatus[4];
     private final ChunkAccess[] lastChunk = new ChunkAccess[4];
-    @Nullable
-    @VisibleForDebug
-    private NaturalSpawner.SpawnState lastSpawnState;
+    // Folia - moved to regionised world data
     // Paper start
-    public final io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet<LevelChunk> tickingChunks = new io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet<>(4096, 0.75f, 4096, 0.15, true);
-    public final io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet<LevelChunk> entityTickingChunks = new io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet<>(4096, 0.75f, 4096, 0.15, true);
+    // Folia - region threading - move to regionised world data
     final com.destroystokyo.paper.util.concurrent.WeakSeqLock loadedChunkMapSeqLock = new com.destroystokyo.paper.util.concurrent.WeakSeqLock();
-    final it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<LevelChunk> loadedChunkMap = new it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<>(8192, 0.5f);
+    final ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable<LevelChunk> loadedChunkMap = new ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable<>(8192, 0.5f); // Folia - region threading
     final java.util.concurrent.atomic.AtomicLong chunkFutureAwaitCounter = new java.util.concurrent.atomic.AtomicLong(); // Paper - chunk system rewrite
-    private final LevelChunk[] lastLoadedChunks = new LevelChunk[4 * 4];
+    // Folia - region threading
     // Paper end
 
     public ServerChunkCache(ServerLevel world, LevelStorageSource.LevelStorageAccess session, DataFixer dataFixer, StructureTemplateManager structureTemplateManager, Executor workerExecutor, ChunkGenerator chunkGenerator, int viewDistance, int simulationDistance, boolean dsync, ChunkProgressListener worldGenerationProgressListener, ChunkStatusUpdateListener chunkStatusChangeListener, Supplier<DimensionDataStorage> persistentStateManagerFactory) {
@@ -107,52 +104,23 @@ public class ServerChunkCache extends ChunkSource {
     }
 
     public void addLoadedChunk(LevelChunk chunk) {
-        this.loadedChunkMapSeqLock.acquireWrite();
-        try {
+        synchronized (this.loadedChunkMap) { // Folia - region threading
             this.loadedChunkMap.put(chunk.coordinateKey, chunk);
-        } finally {
-            this.loadedChunkMapSeqLock.releaseWrite();
-        }
-
-        // rewrite cache if we have to
-        // we do this since we also cache null chunks
-        int cacheKey = getChunkCacheKey(chunk.locX, chunk.locZ);
+        } // Folia - region threading
 
-        this.lastLoadedChunks[cacheKey] = chunk;
+        // Folia - region threading
     }
 
     public void removeLoadedChunk(LevelChunk chunk) {
-        this.loadedChunkMapSeqLock.acquireWrite();
-        try {
+        synchronized (this.loadedChunkMap) { // Folia - region threading
             this.loadedChunkMap.remove(chunk.coordinateKey);
-        } finally {
-            this.loadedChunkMapSeqLock.releaseWrite();
-        }
-
-        // rewrite cache if we have to
-        // we do this since we also cache null chunks
-        int cacheKey = getChunkCacheKey(chunk.locX, chunk.locZ);
+        } // Folia - region threading
 
-        LevelChunk cachedChunk = this.lastLoadedChunks[cacheKey];
-        if (cachedChunk != null && cachedChunk.coordinateKey == chunk.coordinateKey) {
-            this.lastLoadedChunks[cacheKey] = null;
-        }
+        // Folia - region threading
     }
 
     public final LevelChunk getChunkAtIfLoadedMainThread(int x, int z) {
-        int cacheKey = getChunkCacheKey(x, z);
-
-        LevelChunk cachedChunk = this.lastLoadedChunks[cacheKey];
-        if (cachedChunk != null && cachedChunk.locX == x & cachedChunk.locZ == z) {
-            return cachedChunk;
-        }
-
-        long chunkKey = ChunkPos.asLong(x, z);
-
-        cachedChunk = this.loadedChunkMap.get(chunkKey);
-        // Skipping a null check to avoid extra instructions to improve inline capability
-        this.lastLoadedChunks[cacheKey] = cachedChunk;
-        return cachedChunk;
+        return this.loadedChunkMap.get(ChunkPos.asLong(x, z)); // Folia - region threading
     }
 
     public final LevelChunk getChunkAtIfLoadedMainThreadNoCache(int x, int z) {
@@ -197,26 +165,7 @@ public class ServerChunkCache extends ChunkSource {
     public LevelChunk getChunkAtIfLoadedImmediately(int x, int z) {
         long k = ChunkPos.asLong(x, z);
 
-        if (io.papermc.paper.util.TickThread.isTickThread()) { // Paper - rewrite chunk system
-            return this.getChunkAtIfLoadedMainThread(x, z);
-        }
-
-        LevelChunk ret = null;
-        long readlock;
-        do {
-            readlock = this.loadedChunkMapSeqLock.acquireRead();
-            try {
-                ret = this.loadedChunkMap.get(k);
-            } catch (Throwable thr) {
-                if (thr instanceof ThreadDeath) {
-                    throw (ThreadDeath)thr;
-                }
-                // re-try, this means a CME occurred...
-                continue;
-            }
-        } while (!this.loadedChunkMapSeqLock.tryReleaseRead(readlock));
-
-        return ret;
+        return this.loadedChunkMap.get(k); // Folia - region threading
     }
     // Paper end
 
@@ -314,6 +263,7 @@ public class ServerChunkCache extends ChunkSource {
     }
 
     public CompletableFuture<Either<ChunkAccess, ChunkHolder.ChunkLoadingFailure>> getChunkFuture(int chunkX, int chunkZ, ChunkStatus leastStatus, boolean create) {
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         boolean flag1 = io.papermc.paper.util.TickThread.isTickThread(); // Paper - rewrite chunk system
         CompletableFuture completablefuture;
 
@@ -499,10 +449,11 @@ public class ServerChunkCache extends ChunkSource {
     }
 
     private void tickChunks() {
-        long i = this.level.getGameTime();
-        long j = i - this.lastInhabitedUpdate;
+        io.papermc.paper.threadedregions.RegionizedWorldData regionizedWorldData = this.level.getCurrentWorldData(); // Folia - region threading
+        //long i = this.level.getGameTime(); // Folia - region threading
+        long j = 1; // Folia - region threading
 
-        this.lastInhabitedUpdate = i;
+        //this.lastInhabitedUpdate = i; // Folia - region threading
         if (!this.level.isDebug()) {
             ProfilerFiller gameprofilerfiller = this.level.getProfiler();
 
@@ -522,7 +473,7 @@ public class ServerChunkCache extends ChunkSource {
                 NaturalSpawner.SpawnState spawnercreature_d; // moved down
                 if ((this.spawnFriendlies || this.spawnEnemies) && this.level.paperConfig().entities.spawning.perPlayerMobSpawns) { // don't count mobs when animals and monsters are disabled
                     // re-set mob counts
-                    for (ServerPlayer player : this.level.players) {
+                    for (ServerPlayer player : this.level.getLocalPlayers()) { // Folia - region threading
                         // Paper start - per player mob spawning backoff
                         for (int ii = 0; ii < ServerPlayer.MOBCATEGORY_TOTAL_ENUMS; ii++) {
                             player.mobCounts[ii] = 0;
@@ -535,22 +486,22 @@ public class ServerChunkCache extends ChunkSource {
                         }
                         // Paper end - per player mob spawning backoff
                     }
-                    spawnercreature_d = NaturalSpawner.createState(naturalSpawnChunkCount, this.level.getAllEntities(), this::getFullChunk, null, true);
+                    spawnercreature_d = NaturalSpawner.createState(naturalSpawnChunkCount, regionizedWorldData.getLoadedEntities(), this::getFullChunk, null, true); // Folia - region threading - note: function only cares about loaded entities, doesn't need all
                 } else {
-                    spawnercreature_d = NaturalSpawner.createState(naturalSpawnChunkCount, this.level.getAllEntities(), this::getFullChunk, !this.level.paperConfig().entities.spawning.perPlayerMobSpawns ? new LocalMobCapCalculator(this.chunkMap) : null, false);
+                    spawnercreature_d = NaturalSpawner.createState(naturalSpawnChunkCount, regionizedWorldData.getLoadedEntities(), this::getFullChunk, !this.level.paperConfig().entities.spawning.perPlayerMobSpawns ? new LocalMobCapCalculator(this.chunkMap) : null, false); // Folia - region threading - note: function only cares about loaded entities, doesn't need all
                 }
                 // Paper end - Optional per player mob spawns
                 this.level.timings.countNaturalMobs.stopTiming(); // Paper - timings
 
-                this.lastSpawnState = spawnercreature_d;
+                regionizedWorldData.lastSpawnState = spawnercreature_d; // Folia - region threading
                 gameprofilerfiller.popPush("spawnAndTick");
-                boolean flag = this.level.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && !this.level.players().isEmpty(); // CraftBukkit
+                boolean flag = this.level.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && !this.level.getLocalPlayers().isEmpty(); // CraftBukkit // Folia - region threadin
 
                 // Paper start - optimise chunk tick iteration
                 ChunkMap playerChunkMap = this.chunkMap;
-                for (ServerPlayer player : this.level.players) {
+                for (ServerPlayer player : this.level.getLocalPlayers()) { // Folia - region threading
                     if (!player.affectsSpawning || player.isSpectator()) {
-                        playerChunkMap.playerMobSpawnMap.remove(player);
+                        regionizedWorldData.mobSpawnMap.remove(player); // Folia - region threading
                         player.playerNaturallySpawnedEvent = null;
                         player.lastEntitySpawnRadiusSquared = -1.0;
                         continue;
@@ -566,7 +517,7 @@ public class ServerChunkCache extends ChunkSource {
                     com.destroystokyo.paper.event.entity.PlayerNaturallySpawnCreaturesEvent event = new com.destroystokyo.paper.event.entity.PlayerNaturallySpawnCreaturesEvent(player.getBukkitEntity(), (byte)chunkRange);
                     event.callEvent();
                     if (event.isCancelled() || event.getSpawnRadius() < 0) {
-                        playerChunkMap.playerMobSpawnMap.remove(player);
+                        regionizedWorldData.mobSpawnMap.remove(player); // Folia - region threading
                         player.playerNaturallySpawnedEvent = null;
                         player.lastEntitySpawnRadiusSquared = -1.0;
                         continue;
@@ -576,13 +527,13 @@ public class ServerChunkCache extends ChunkSource {
                     int chunkX = io.papermc.paper.util.CoordinateUtils.getChunkCoordinate(player.getX());
                     int chunkZ = io.papermc.paper.util.CoordinateUtils.getChunkCoordinate(player.getZ());
 
-                    playerChunkMap.playerMobSpawnMap.addOrUpdate(player, chunkX, chunkZ, range);
+                    regionizedWorldData.mobSpawnMap.addOrUpdate(player, chunkX, chunkZ, range); // Folia - region threading
                     player.lastEntitySpawnRadiusSquared = (double)((range << 4) * (range << 4)); // used in anyPlayerCloseEnoughForSpawning
                     player.playerNaturallySpawnedEvent = event;
                 }
                 // Paper end - optimise chunk tick iteration
                 int l = this.level.getGameRules().getInt(GameRules.RULE_RANDOMTICKING);
-                boolean flag1 = this.level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) != 0L && this.level.getLevelData().getGameTime() % this.level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) == 0L; // CraftBukkit
+                boolean flag1 = this.level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) != 0L && this.level.getRedstoneGameTime() % this.level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) == 0L; // CraftBukkit // Folia - region threading
                 // Paper - optimise chunk tick iteration
 
                 int chunksTicked = 0; // Paper
@@ -590,10 +541,10 @@ public class ServerChunkCache extends ChunkSource {
                 io.papermc.paper.util.player.NearbyPlayers nearbyPlayers = this.chunkMap.getNearbyPlayers(); // Paper - optimise chunk tick iteration
                 Iterator<LevelChunk> chunkIterator;
                 if (this.level.paperConfig().entities.spawning.perPlayerMobSpawns) {
-                    chunkIterator = this.tickingChunks.iterator();
+                    chunkIterator = regionizedWorldData.getTickingChunks().iterator(); // Folia - region threading
                 } else {
-                    chunkIterator = this.tickingChunks.unsafeIterator();
-                    List<LevelChunk> shuffled = Lists.newArrayListWithCapacity(this.tickingChunks.size());
+                    chunkIterator = regionizedWorldData.getTickingChunks().unsafeIterator(); // Folia - region threading
+                    List<LevelChunk> shuffled = Lists.newArrayListWithCapacity(regionizedWorldData.getTickingChunks().size()); // Folia - region threading
                     while (chunkIterator.hasNext()) {
                         shuffled.add(chunkIterator.next());
                     }
@@ -663,17 +614,21 @@ public class ServerChunkCache extends ChunkSource {
             // Paper - optimise chunk tick iteration
                 this.level.timings.broadcastChunkUpdates.startTiming(); // Paper - timing
             // Paper start - optimise chunk tick iteration
-            if (!this.chunkMap.needsChangeBroadcasting.isEmpty()) {
-                it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<ChunkHolder> copy = this.chunkMap.needsChangeBroadcasting.clone();
-                this.chunkMap.needsChangeBroadcasting.clear();
-                for (ChunkHolder holder : copy) {
-                    holder.broadcastChanges(holder.getFullChunkNowUnchecked()); // LevelChunks are NEVER unloaded
-                    if (holder.needsBroadcastChanges()) {
-                        // I DON'T want to KNOW what DUMB plugins might be doing.
-                        this.chunkMap.needsChangeBroadcasting.add(holder);
+            // Folia start - region threading
+            if (!this.level.needsChangeBroadcasting.isEmpty()) {
+                for (Iterator<ChunkHolder> iterator = this.level.needsChangeBroadcasting.iterator(); iterator.hasNext();) {
+                    ChunkHolder holder = iterator.next();
+                    if (!io.papermc.paper.util.TickThread.isTickThreadFor(holder.newChunkHolder.world, holder.pos)) {
+                        continue;
+                    }
+                    // don't need to worry about asynchronous chunk holder remove, as that can only be done by this tick thread
+                    holder.broadcastChanges(holder.getFullChunkNowUnchecked());
+                    if (!holder.needsBroadcastChanges()) {
+                        iterator.remove();
                     }
                 }
             }
+            // Folia end - region threading
             // Paper end - optimise chunk tick iteration
                 this.level.timings.broadcastChunkUpdates.stopTiming(); // Paper - timing
             // Paper - optimise chunk tick iteration
@@ -736,14 +691,19 @@ public class ServerChunkCache extends ChunkSource {
 
     @Override
     public void onLightUpdate(LightLayer type, SectionPos pos) {
-        this.mainThreadProcessor.execute(() -> {
+        Runnable run = () -> { // Folia - region threading
             ChunkHolder playerchunk = this.getVisibleChunkIfPresent(pos.chunk().toLong());
 
             if (playerchunk != null) {
                 playerchunk.sectionLightChanged(type, pos.y());
             }
 
-        });
+        }; // Folia - region threading
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueChunkTask(
+            this.level, pos.getX(), pos.getZ(), run
+        );
+        // Folia end - region threading
     }
 
     public <T> void addRegionTicket(TicketType<T> ticketType, ChunkPos pos, int radius, T argument) {
@@ -815,7 +775,8 @@ public class ServerChunkCache extends ChunkSource {
     @Nullable
     @VisibleForDebug
     public NaturalSpawner.SpawnState getLastSpawnState() {
-        return this.lastSpawnState;
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.level.getCurrentWorldData(); // Folia - region threading
+        return worldData == null ? null : worldData.lastSpawnState; // Folia - region threading
     }
 
     public void removeTicketsOnClosing() {
@@ -848,8 +809,43 @@ public class ServerChunkCache extends ChunkSource {
             return ServerChunkCache.this.mainThread;
         }
 
+        // Folia start - region threading
+        @Override
+        public void tell(Runnable runnable) {
+            if (true) {
+                throw new UnsupportedOperationException();
+            }
+            super.tell(runnable);
+        }
+
+        @Override
+        public void executeBlocking(Runnable runnable) {
+            if (true) {
+                throw new UnsupportedOperationException();
+            }
+            super.executeBlocking(runnable);
+        }
+
+        @Override
+        public void execute(Runnable runnable) {
+            if (true) {
+                throw new UnsupportedOperationException();
+            }
+            super.execute(runnable);
+        }
+
+        @Override
+        public void executeIfPossible(Runnable runnable) {
+            if (true) {
+                throw new UnsupportedOperationException();
+            }
+            super.executeIfPossible(runnable);
+        }
+        // Folia end - region threading
+
         @Override
         protected void doRunTask(Runnable task) {
+            if (true) throw new UnsupportedOperationException(); // Folia - region threading
             ServerChunkCache.this.level.getProfiler().incrementCounter("runTask");
             super.doRunTask(task);
         }
@@ -857,10 +853,15 @@ public class ServerChunkCache extends ChunkSource {
         @Override
         // CraftBukkit start - process pending Chunk loadCallback() and unloadCallback() after each run task
         public boolean pollTask() {
+            // Folia start - region threading
+            if (ServerChunkCache.this.level != io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().world) {
+                throw new IllegalStateException("Polling tasks from non-owned region");
+            }
+            // Folia end - region threading
             if (ServerChunkCache.this.runDistanceManagerUpdates()) {
                 return true;
             }
-            return super.pollTask() | ServerChunkCache.this.level.chunkTaskScheduler.executeMainThreadTask(); // Paper - rewrite chunk system
+            return io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegion().getData().getTaskQueueData().executeChunkTask(); // Paper - rewrite chunk system // Folia - region threading
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 502bdc726b7890b00ee36871d905dea44e8719e3..2f799ead36f0f22afe7dc4b688e59ef25fe2f9b8 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -193,37 +193,35 @@ public class ServerLevel extends Level implements WorldGenLevel {
     public final ServerChunkCache chunkSource;
     private final MinecraftServer server;
     public final PrimaryLevelData serverLevelData; // CraftBukkit - type
-    final EntityTickList entityTickList;
+    //final EntityTickList entityTickList; // Folia - region threading
     //public final PersistentEntitySectionManager<Entity> entityManager; // Paper - rewrite chunk system
     private final GameEventDispatcher gameEventDispatcher;
     public boolean noSave;
     private final SleepStatus sleepStatus;
     private int emptyTime;
     private final PortalForcer portalForcer;
-    private final LevelTicks<Block> blockTicks;
-    private final LevelTicks<Fluid> fluidTicks;
+    //private final LevelTicks<Block> blockTicks; // Folia - region threading
+    //private final LevelTicks<Fluid> fluidTicks; // Folia - region threading
     final Set<Mob> navigatingMobs;
     volatile boolean isUpdatingNavigations;
     protected final Raids raids;
-    private final ObjectLinkedOpenHashSet<BlockEventData> blockEvents;
-    private final List<BlockEventData> blockEventsToReschedule;
-    private boolean handlingTick;
+    //private final ObjectLinkedOpenHashSet<BlockEventData> blockEvents; // Folia - region threading
+    //private final List<BlockEventData> blockEventsToReschedule; // Folia - region threading
+    //private boolean handlingTick; // Folia - region threading
     private final List<CustomSpawner> customSpawners;
     @Nullable
     private EndDragonFight dragonFight;
     final Int2ObjectMap<EnderDragonPart> dragonParts;
     private final StructureManager structureManager;
     private final StructureCheck structureCheck;
-    private final boolean tickTime;
+    public final boolean tickTime; // Folia - region threading
     private final RandomSequences randomSequences;
-    public long lastMidTickExecuteFailure; // Paper - execute chunk tasks mid tick
+    // Folia - region threading
 
     // CraftBukkit start
     public final LevelStorageSource.LevelStorageAccess convertable;
     public final UUID uuid;
-    public boolean hasPhysicsEvent = true; // Paper - BlockPhysicsEvent
-    public boolean hasEntityMoveEvent; // Paper - Add EntityMoveEvent
-    private final alternate.current.wire.WireHandler wireHandler = new alternate.current.wire.WireHandler(this); // Paper - optimize redstone (Alternate Current)
+    // Folia - region threading - move to regionised world data
 
     public LevelChunk getChunkIfLoaded(int x, int z) {
         return this.chunkSource.getChunkAtIfLoadedImmediately(x, z); // Paper - Use getChunkIfLoadedImmediately
@@ -253,6 +251,36 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
         ServerChunkCache chunkProvider = this.getChunkSource();
 
+        // Folia start - region threading
+        // don't let players move into regions not owned
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(this, minChunkX, minChunkZ, maxChunkX, maxChunkZ)) {
+            return false;
+        }
+
+        for (int cx = minChunkX; cx <= maxChunkX; ++cx) {
+            for (int cz = minChunkZ; cz <= maxChunkZ; ++cz) {
+                if (chunkProvider.getChunkAtIfLoadedImmediately(cx, cz) == null) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    public final boolean isAreaLoaded(final BlockPos center, final int radius) {
+        int minX = (center.getX() - radius) >> 4;
+        int minZ = (center.getZ() - radius) >> 4;
+        int maxX = (center.getX() + radius) >> 4;
+        int maxZ = (center.getZ() + radius) >> 4;
+
+        return this.isAreaLoaded(minX, minZ, maxX, maxZ);
+    }
+
+    public final boolean isAreaLoaded(final int minChunkX, final int minChunkZ, final int maxChunkX, final int maxChunkZ) {
+        // Folia end - region threading
+        ServerChunkCache chunkProvider = this.getChunkSource();
+
         for (int cx = minChunkX; cx <= maxChunkX; ++cx) {
             for (int cz = minChunkZ; cz <= maxChunkZ; ++cz) {
                 if (chunkProvider.getChunkAtIfLoadedImmediately(cx, cz) == null) {
@@ -511,7 +539,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     public final int getRegionChunkShift() {
         // placeholder for folia
-        return io.papermc.paper.threadedregions.TickRegions.getRegionChunkShift();
+        return this.regioniser.sectionChunkShift; // Folia - region threading
     }
     // Paper end - rewrite chunk system
 
@@ -566,14 +594,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
     // Paper end - optimise getPlayerByUUID
     // Paper start - lag compensation
-    private long lagCompensationTick = net.minecraft.server.MinecraftServer.SERVER_INIT;
+    // Folia - region threading
 
     public long getLagCompensationTick() {
-        return this.lagCompensationTick;
+        return this.getCurrentWorldData().getLagCompensationTick(); // Folia - region threading
     }
 
     public void updateLagCompensationTick() {
-        this.lagCompensationTick = (System.nanoTime() - net.minecraft.server.MinecraftServer.SERVER_INIT) / (java.util.concurrent.TimeUnit.MILLISECONDS.toNanos(50L));
+        throw new UnsupportedOperationException(); // Folia - region threading
     }
     // Paper end - lag compensation
     // Paper start - optimise nearby player retrieval
@@ -620,7 +648,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
             ServerPlayer nearest = null;
             double nearestDist = Double.MAX_VALUE;
 
-            for (ServerPlayer player : this.players()) {
+            for (ServerPlayer player : this.getLocalPlayers()) { // Folia - region threading
                 double dist = player.distanceToSqr(x, y, z);
                 if (dist >= nearestDist) {
                     continue;
@@ -676,7 +704,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
             return nearest;
         } else {
-            return this.getNearestEntity(this.players(), targetPredicate, entity, x, y, z);
+            return this.getNearestEntity(this.getLocalPlayers(), targetPredicate, entity, x, y, z); // Folia - region threading
         }
     }
 
@@ -685,6 +713,58 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return this.getNearestPlayer(targetPredicate, null, x, y, z);
     }
     // Paper end - optimise nearby player retrieval
+    // Folia start - region threading
+    public final io.papermc.paper.threadedregions.TickRegions tickRegions = new io.papermc.paper.threadedregions.TickRegions();
+    public final io.papermc.paper.threadedregions.ThreadedRegionizer<io.papermc.paper.threadedregions.TickRegions.TickRegionData, io.papermc.paper.threadedregions.TickRegions.TickRegionSectionData> regioniser;
+    {
+        this.regioniser = new io.papermc.paper.threadedregions.ThreadedRegionizer<>(
+            (int)Math.max(1L, (8L * 16L * 16L) / (1L << (2 * (io.papermc.paper.threadedregions.TickRegions.getRegionChunkShift())))),
+            (1.0 / 6.0),
+            Math.max(1, 8 / (1 << io.papermc.paper.threadedregions.TickRegions.getRegionChunkShift())),
+            1,
+            io.papermc.paper.threadedregions.TickRegions.getRegionChunkShift(),
+            this,
+            this.tickRegions
+        );
+    }
+    public final io.papermc.paper.threadedregions.RegionizedTaskQueue.WorldRegionTaskData taskQueueRegionData = new io.papermc.paper.threadedregions.RegionizedTaskQueue.WorldRegionTaskData(this);
+    public static final int WORLD_INIT_NOT_CHECKED = 0;
+    public static final int WORLD_INIT_CHECKING = 1;
+    public static final int WORLD_INIT_CHECKED = 2;
+    public final java.util.concurrent.atomic.AtomicInteger checkInitialised = new java.util.concurrent.atomic.AtomicInteger(WORLD_INIT_NOT_CHECKED);
+    public ChunkPos randomSpawnSelection;
+
+    public static final record PendingTeleport(Entity.EntityTreeNode rootVehicle, Vec3 to) {}
+    private final it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<PendingTeleport> pendingTeleports = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>();
+
+    public void pushPendingTeleport(final PendingTeleport teleport) {
+        synchronized (this.pendingTeleports) {
+            this.pendingTeleports.add(teleport);
+        }
+    }
+
+    public boolean removePendingTeleport(final PendingTeleport teleport) {
+        synchronized (this.pendingTeleports) {
+            return this.pendingTeleports.remove(teleport);
+        }
+    }
+
+    public List<PendingTeleport> removeAllRegionTeleports() {
+        final List<PendingTeleport> ret = new ArrayList<>();
+
+        synchronized (this.pendingTeleports) {
+            for (final Iterator<PendingTeleport> iterator = this.pendingTeleports.iterator(); iterator.hasNext(); ) {
+                final PendingTeleport pendingTeleport = iterator.next();
+                if (io.papermc.paper.util.TickThread.isTickThreadFor(this, pendingTeleport.to())) {
+                    ret.add(pendingTeleport);
+                    iterator.remove();
+                }
+            }
+        }
+
+        return ret;
+    }
+    // Folia end - region threading
 
     // Add env and gen to constructor, IWorldDataServer -> WorldDataServer
     public ServerLevel(MinecraftServer minecraftserver, Executor executor, LevelStorageSource.LevelStorageAccess convertable_conversionsession, PrimaryLevelData iworlddataserver, ResourceKey<Level> resourcekey, LevelStem worlddimension, ChunkProgressListener worldloadlistener, boolean flag, long i, List<CustomSpawner> list, boolean flag1, @Nullable RandomSequences randomsequences, org.bukkit.World.Environment env, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider) {
@@ -697,13 +777,13 @@ public class ServerLevel extends Level implements WorldGenLevel {
         this.convertable = convertable_conversionsession;
         this.uuid = WorldUUID.getUUID(convertable_conversionsession.levelDirectory.path().toFile());
         // CraftBukkit end
-        this.players = Lists.newArrayList();
-        this.entityTickList = new EntityTickList();
-        this.blockTicks = new LevelTicks<>(this::isPositionTickingWithEntitiesLoaded, this.getProfilerSupplier());
-        this.fluidTicks = new LevelTicks<>(this::isPositionTickingWithEntitiesLoaded, this.getProfilerSupplier());
+        this.players = new java.util.concurrent.CopyOnWriteArrayList<>(); // Folia - region threading
+        //this.entityTickList = new EntityTickList(); // Folia - region threading
+        //this.blockTicks = new LevelTicks<>(this::isPositionTickingWithEntitiesLoaded, this.getProfilerSupplier()); // Folia - moved to RegioniedWorldData
+        //this.fluidTicks = new LevelTicks<>(this::isPositionTickingWithEntitiesLoaded, this.getProfilerSupplier()); // Folia - moved to RegioniedWorldData
         this.navigatingMobs = new ObjectOpenHashSet();
-        this.blockEvents = new ObjectLinkedOpenHashSet();
-        this.blockEventsToReschedule = new ArrayList(64);
+        //this.blockEvents = new ObjectLinkedOpenHashSet(); // Folia - moved to RegioniedWorldData
+        //this.blockEventsToReschedule = new ArrayList(64); // Folia - moved to RegioniedWorldData
         this.dragonParts = new Int2ObjectOpenHashMap();
         this.tickTime = flag1;
         this.server = minecraftserver;
@@ -742,7 +822,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         });
         this.chunkSource.getGeneratorState().ensureStructuresGenerated();
         this.portalForcer = new PortalForcer(this);
-        this.updateSkyBrightness();
+        //this.updateSkyBrightness(); // Folia - region threading - delay until first tick
         this.prepareWeather();
         this.getWorldBorder().setAbsoluteMaxSize(minecraftserver.getAbsoluteMaxWorldSize());
         this.raids = (Raids) this.getDataStorage().computeIfAbsent(Raids.factory(this), Raids.getFileId(this.dimensionTypeRegistration()));
@@ -769,7 +849,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
         this.chunkTaskScheduler = new io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler(this, io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler.workerThreads); // Paper - rewrite chunk system
         this.entityLookup = new io.papermc.paper.chunk.system.entity.EntityLookup(this, new EntityCallbacks()); // Paper - rewrite chunk system
+        this.updateTickData(); // Folia - region threading - make sure it is initialised before ticked
+    }
+
+    // Folia start - region threading
+    public void updateTickData() {
+        this.tickData = new io.papermc.paper.threadedregions.RegionizedServer.WorldLevelData(this, this.serverLevelData.getGameTime(), this.serverLevelData.getDayTime());
     }
+    // Folia end - region threading
 
     // Paper start
     @Override
@@ -802,44 +889,27 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return this.structureManager;
     }
 
-    public void tick(BooleanSupplier shouldKeepTicking) {
+    public void tick(BooleanSupplier shouldKeepTicking, io.papermc.paper.threadedregions.TickRegions.TickRegionData region) { // Folia - regionised ticking
+        final io.papermc.paper.threadedregions.RegionizedWorldData regionizedWorldData = this.getCurrentWorldData(); // Folia - regionised ticking
         ProfilerFiller gameprofilerfiller = this.getProfiler();
 
-        this.handlingTick = true;
+        regionizedWorldData.setHandlingTick(true); // Folia - regionised ticking
         TickRateManager tickratemanager = this.tickRateManager();
         boolean flag = tickratemanager.runsNormally();
 
         if (flag) {
             gameprofilerfiller.push("world border");
-            this.getWorldBorder().tick();
+            if (region == null) this.getWorldBorder().tick(); // Folia - regionised ticking
             gameprofilerfiller.popPush("weather");
-            this.advanceWeatherCycle();
+            if (region == null) this.advanceWeatherCycle(); // Folia - regionised ticking
         }
 
-        int i = this.getGameRules().getInt(GameRules.RULE_PLAYERS_SLEEPING_PERCENTAGE);
+        //int i = this.getGameRules().getInt(GameRules.RULE_PLAYERS_SLEEPING_PERCENTAGE); // Folia - region threading - move into tickSleep
         long j;
 
-        if (this.sleepStatus.areEnoughSleeping(i) && this.sleepStatus.areEnoughDeepSleeping(i, this.players)) {
-            // CraftBukkit start
-            j = this.levelData.getDayTime() + 24000L;
-            TimeSkipEvent event = new TimeSkipEvent(this.getWorld(), TimeSkipEvent.SkipReason.NIGHT_SKIP, (j - j % 24000L) - this.getDayTime());
-            if (this.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT)) {
-                this.getCraftServer().getPluginManager().callEvent(event);
-                if (!event.isCancelled()) {
-                    this.setDayTime(this.getDayTime() + event.getSkipAmount());
-                }
-            }
+        if (region == null) this.tickSleep(); // Folia - region threading
 
-            if (!event.isCancelled()) {
-                this.wakeUpAllPlayers();
-            }
-            // CraftBukkit end
-            if (this.getGameRules().getBoolean(GameRules.RULE_WEATHER_CYCLE) && this.isRaining()) {
-                this.resetWeatherCycle();
-            }
-        }
-
-        this.updateSkyBrightness();
+        if (region == null) this.updateSkyBrightness(); // Folia - region threading
         if (flag) {
             this.tickTime();
         }
@@ -847,11 +917,11 @@ public class ServerLevel extends Level implements WorldGenLevel {
         gameprofilerfiller.popPush("tickPending");
         this.timings.scheduledBlocks.startTiming(); // Paper
         if (!this.isDebug() && flag) {
-            j = this.getGameTime();
+            j = regionizedWorldData.getRedstoneGameTime(); // Folia - region threading
             gameprofilerfiller.push("blockTicks");
-            this.blockTicks.tick(j, paperConfig().environment.maxBlockTicks, this::tickBlock); // Paper - configurable max block ticks
+            regionizedWorldData.getBlockLevelTicks().tick(j, paperConfig().environment.maxBlockTicks, this::tickBlock); // Paper - configurable max block ticks // Folia - region ticking
             gameprofilerfiller.popPush("fluidTicks");
-            this.fluidTicks.tick(j, paperConfig().environment.maxFluidTicks, this::tickFluid); // Paper - configurable max fluid ticks
+            regionizedWorldData.getFluidLevelTicks().tick(j, paperConfig().environment.maxFluidTicks, this::tickFluid); // Paper - configurable max fluid ticks // Folia - region ticking
             gameprofilerfiller.pop();
         }
         this.timings.scheduledBlocks.stopTiming(); // Paper
@@ -874,9 +944,9 @@ public class ServerLevel extends Level implements WorldGenLevel {
             this.timings.doSounds.stopTiming(); // Spigot
         }
 
-        this.handlingTick = false;
+        regionizedWorldData.setHandlingTick(false); // Folia - regionised ticking
         gameprofilerfiller.pop();
-        boolean flag1 = !paperConfig().unsupportedSettings.disableWorldTickingWhenEmpty || !this.players.isEmpty() || !this.getForcedChunks().isEmpty(); // CraftBukkit - this prevents entity cleanup, other issues on servers with no players // Paper - restore this
+        boolean flag1 = true || !this.players.isEmpty() || !this.getForcedChunks().isEmpty(); // CraftBukkit - this prevents entity cleanup, other issues on servers with no players // Paper - restore this // Folia - unrestore this, we always need to tick empty worlds
 
         if (flag1) {
             this.resetEmptyTime();
@@ -886,20 +956,30 @@ public class ServerLevel extends Level implements WorldGenLevel {
             gameprofilerfiller.push("entities");
             this.timings.tickEntities.startTiming(); // Spigot
             if (this.dragonFight != null && flag) {
+                if (io.papermc.paper.util.TickThread.isTickThreadFor(this, this.dragonFight.origin)) { // Folia - region threading
                 gameprofilerfiller.push("dragonFight");
                 this.dragonFight.tick();
                 gameprofilerfiller.pop();
+                } else { // Folia start - region threading
+                    // try to load dragon fight
+                    ChunkPos fightCenter = new ChunkPos(this.dragonFight.origin);
+                    this.chunkSource.addTicketAtLevel(
+                        TicketType.UNKNOWN, fightCenter, io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+                        fightCenter
+                    );
+                } // Folia end - region threading
             }
 
             org.spigotmc.ActivationRange.activateEntities(this); // Spigot
             this.timings.entityTick.startTiming(); // Spigot
-            this.entityTickList.forEach((entity) -> {
+            regionizedWorldData.forEachTickingEntity((entity) -> { // Folia - regionised ticking
                 if (!entity.isRemoved()) {
                     if (false && this.shouldDiscardEntity(entity)) { // CraftBukkit - We prevent spawning in general, so this butchering is not needed
                         entity.discard();
                     } else if (!tickratemanager.isEntityFrozen(entity)) {
                         gameprofilerfiller.push("checkDespawn");
                         entity.checkDespawn();
+                        if (entity.isRemoved()) return; // Folia - region threading - if we despawned, DON'T TICK IT!
                         gameprofilerfiller.pop();
                         if (true || this.chunkSource.chunkMap.getDistanceManager().inEntityTickingRange(entity.chunkPosition().toLong())) { // Paper - now always true if in the ticking list
                             Entity entity1 = entity.getVehicle();
@@ -930,6 +1010,31 @@ public class ServerLevel extends Level implements WorldGenLevel {
         gameprofilerfiller.pop();
     }
 
+    // Folia start - region threading
+    public void tickSleep() {
+        int i = this.getGameRules().getInt(GameRules.RULE_PLAYERS_SLEEPING_PERCENTAGE); long j; // Folia moved from tick loop
+        if (this.sleepStatus.areEnoughSleeping(i) && this.sleepStatus.areEnoughDeepSleeping(i, this.players)) {
+            // CraftBukkit start
+            j = this.levelData.getDayTime() + 24000L;
+            TimeSkipEvent event = new TimeSkipEvent(this.getWorld(), TimeSkipEvent.SkipReason.NIGHT_SKIP, (j - j % 24000L) - this.getDayTime());
+            if (this.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT)) {
+                this.getCraftServer().getPluginManager().callEvent(event);
+                if (!event.isCancelled()) {
+                    this.setDayTime(this.getDayTime() + event.getSkipAmount());
+                }
+            }
+
+            if (!event.isCancelled()) {
+                this.wakeUpAllPlayers();
+            }
+            // CraftBukkit end
+            if (this.getGameRules().getBoolean(GameRules.RULE_WEATHER_CYCLE) && this.isRaining()) {
+                this.resetWeatherCycle();
+            }
+        }
+    }
+    // Folia end - region threading
+
     @Override
     public boolean shouldTickBlocksAt(long chunkPos) {
         // Paper start - replace player chunk loader system
@@ -940,11 +1045,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     protected void tickTime() {
         if (this.tickTime) {
-            long i = this.levelData.getGameTime() + 1L;
+            io.papermc.paper.threadedregions.RegionizedWorldData regionizedWorldData = this.getCurrentWorldData(); // Folia - region threading
+            long i = regionizedWorldData.getRedstoneGameTime() + 1L; // Folia - region threading
 
-            this.serverLevelData.setGameTime(i);
-            this.serverLevelData.getScheduledEvents().tick(this.server, i);
-            if (this.levelData.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT)) {
+            regionizedWorldData.setRedstoneGameTime(i); // Folia - region threading
+            if (false) this.serverLevelData.getScheduledEvents().tick(this.server, i); // Folia - region threading - TODO any way to bring this in?
+            if (false && this.levelData.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT)) { // Folia - region threading
                 this.setDayTime(this.levelData.getDayTime() + 1L);
             }
 
@@ -973,15 +1079,23 @@ public class ServerLevel extends Level implements WorldGenLevel {
     private void wakeUpAllPlayers() {
         this.sleepStatus.removeAllSleepers();
         (this.players.stream().filter(LivingEntity::isSleeping).collect(Collectors.toList())).forEach((entityplayer) -> { // CraftBukkit - decompile error
-            entityplayer.stopSleepInBed(false, false);
+            // Folia start - region threading
+            entityplayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                if (player.level() != ServerLevel.this || !player.isSleeping()) {
+                    return;
+                }
+                player.stopSleepInBed(false, false);
+            }, null, 1L);
+            // Folia end - region threading
         });
     }
     // Paper start - optimise random block ticking
-    private final BlockPos.MutableBlockPos chunkTickMutablePosition = new BlockPos.MutableBlockPos();
-    private final io.papermc.paper.util.math.ThreadUnsafeRandom randomTickRandom = new io.papermc.paper.util.math.ThreadUnsafeRandom(this.random.nextLong());
+    private final ThreadLocal<BlockPos.MutableBlockPos> chunkTickMutablePosition = ThreadLocal.withInitial(() -> new BlockPos.MutableBlockPos()); // Folia - region threading
+    private final ThreadLocal<io.papermc.paper.util.math.ThreadUnsafeRandom> randomTickRandom = ThreadLocal.withInitial(() -> new io.papermc.paper.util.math.ThreadUnsafeRandom(this.random.nextLong())); // Folia - region threading
     // Paper end
 
     public void tickChunk(LevelChunk chunk, int randomTickSpeed) {
+        io.papermc.paper.util.math.ThreadUnsafeRandom randomTickRandom = this.randomTickRandom.get(); // Folia - region threading
         ChunkPos chunkcoordintpair = chunk.getPos();
         boolean flag = this.isRaining();
         int j = chunkcoordintpair.getMinBlockX();
@@ -989,7 +1103,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         ProfilerFiller gameprofilerfiller = this.getProfiler();
 
         gameprofilerfiller.push("thunder");
-        final BlockPos.MutableBlockPos blockposition = this.chunkTickMutablePosition; // Paper - use mutable to reduce allocation rate, final to force compile fail on change
+        final BlockPos.MutableBlockPos blockposition = this.chunkTickMutablePosition.get(); // Paper - use mutable to reduce allocation rate, final to force compile fail on change // Folia - region threading
 
         if (!this.paperConfig().environment.disableThunder && flag && this.isThundering() && this.spigotConfig.thunderChance > 0 && this.random.nextInt(this.spigotConfig.thunderChance) == 0) { // Spigot // Paper - Option to disable thunder
             blockposition.set(this.findLightningTargetAround(this.getBlockRandomPos(j, 0, k, 15))); // Paper
@@ -1045,7 +1159,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                 int yPos = (sectionIndex + minSection) << 4;
                 for (int a = 0; a < randomTickSpeed; ++a) {
                     int tickingBlocks = section.tickingList.size();
-                    int index = this.randomTickRandom.nextInt(16 * 16 * 16);
+                    int index = randomTickRandom.nextInt(16 * 16 * 16); // Folia - region threading
                     if (index >= tickingBlocks) {
                         continue;
                     }
@@ -1059,7 +1173,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     BlockPos blockposition2 = blockposition.set(j + randomX, randomY, k + randomZ);
                     BlockState iblockdata = com.destroystokyo.paper.util.maplist.IBlockDataList.getBlockDataFromRaw(raw);
 
-                    iblockdata.randomTick(this, blockposition2, this.randomTickRandom);
+                    iblockdata.randomTick(this, blockposition2, randomTickRandom); // Folia - region threading
                 }
                 // We drop the fluid tick since LAVA is ALREADY TICKED by the above method (See LiquidBlock).
                 // TODO CHECK ON UPDATE (ping the Canadian)
@@ -1164,7 +1278,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public boolean isHandlingTick() {
-        return this.handlingTick;
+        return this.getCurrentWorldData().isHandlingTick(); // Folia - regionised ticking
     }
 
     public boolean canSleepThroughNights() {
@@ -1196,6 +1310,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public void updateSleepingPlayerList() {
+        // Folia start - region threading
+        if (!io.papermc.paper.threadedregions.RegionizedServer.isGlobalTickThread()) {
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+                ServerLevel.this.updateSleepingPlayerList();
+            });
+            return;
+        }
+        // Folia end - region threading
         if (!this.players.isEmpty() && this.sleepStatus.update(this.players)) {
             this.announceSleepStatus();
         }
@@ -1207,7 +1329,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return this.server.getScoreboard();
     }
 
-    private void advanceWeatherCycle() {
+    public void advanceWeatherCycle() { // Folia - region threading - public
         boolean flag = this.isRaining();
 
         if (this.dimensionType().hasSkyLight()) {
@@ -1293,23 +1415,24 @@ public class ServerLevel extends Level implements WorldGenLevel {
             this.server.getPlayerList().broadcastAll(new PacketPlayOutGameStateChange(PacketPlayOutGameStateChange.THUNDER_LEVEL_CHANGE, this.thunderLevel));
         }
         // */
-        for (int idx = 0; idx < this.players.size(); ++idx) {
-            if (((ServerPlayer) this.players.get(idx)).level() == this) {
-                ((ServerPlayer) this.players.get(idx)).tickWeather();
+        ServerPlayer[] players = this.players.toArray(new ServerPlayer[0]); // Folia - region threading
+        for (ServerPlayer player : players) { // Folia - region threading
+            if (player.level() == this) { // Folia - region threading
+                player.tickWeather(); // Folia - region threading
             }
         }
 
         if (flag != this.isRaining()) {
             // Only send weather packets to those affected
-            for (int idx = 0; idx < this.players.size(); ++idx) {
-                if (((ServerPlayer) this.players.get(idx)).level() == this) {
-                    ((ServerPlayer) this.players.get(idx)).setPlayerWeather((!flag ? WeatherType.DOWNFALL : WeatherType.CLEAR), false);
+            for (ServerPlayer player : players) { // Folia - region threading
+                if (player.level() == this) { // Folia - region threading
+                    player.setPlayerWeather((!flag ? WeatherType.DOWNFALL : WeatherType.CLEAR), false); // Folia - region threading
                 }
             }
         }
-        for (int idx = 0; idx < this.players.size(); ++idx) {
-            if (((ServerPlayer) this.players.get(idx)).level() == this) {
-                ((ServerPlayer) this.players.get(idx)).updateWeather(this.oRainLevel, this.rainLevel, this.oThunderLevel, this.thunderLevel);
+        for (ServerPlayer player : players) { // Folia - region threading
+            if (player.level() == this) { // Folia - region threading
+                player.updateWeather(this.oRainLevel, this.rainLevel, this.oThunderLevel, this.thunderLevel); // Folia - region threading
             }
         }
         // CraftBukkit end
@@ -1374,7 +1497,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     public void tickNonPassenger(Entity entity) {
         // Paper start - log detailed entity tick information
-        io.papermc.paper.util.TickThread.ensureTickThread("Cannot tick an entity off-main");
+        io.papermc.paper.util.TickThread.ensureTickThread(entity, "Cannot tick an entity off-main"); // Folia - region threading
         try {
             if (currentlyTickingEntity.get() == null) {
                 currentlyTickingEntity.lazySet(entity);
@@ -1407,7 +1530,16 @@ public class ServerLevel extends Level implements WorldGenLevel {
         if (isActive) { // Paper - EAR 2
             TimingHistory.activatedEntityTicks++;
         entity.tick();
-        entity.postTick(); // CraftBukkit
+        // Folia start - region threading
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(entity)) {
+            // removed from region while ticking
+            return;
+        }
+        if (entity.doPortalLogic()) {
+            // portalled
+            return;
+        }
+        // Folia end - region threading
         } else { entity.inactiveTick(); } // Paper - EAR 2
         this.getProfiler().pop();
         } finally { timer.stopTiming(); } // Paper - timings
@@ -1430,7 +1562,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     private void tickPassenger(Entity vehicle, Entity passenger) {
         if (!passenger.isRemoved() && passenger.getVehicle() == vehicle) {
-            if (passenger instanceof Player || this.entityTickList.contains(passenger)) {
+            if (passenger instanceof Player || this.getCurrentWorldData().hasEntityTickingEntity(passenger)) { // Folia - region threading
                 // Paper - EAR 2
                 final boolean isActive = org.spigotmc.ActivationRange.checkIfActive(passenger);
                 co.aikar.timings.Timing timer = isActive ? passenger.getType().passengerTickTimer.startTiming() : passenger.getType().passengerInactiveTickTimer.startTiming(); // Paper
@@ -1447,7 +1579,16 @@ public class ServerLevel extends Level implements WorldGenLevel {
                 // Paper start - EAR 2
                 if (isActive) {
                 passenger.rideTick();
-                passenger.postTick(); // CraftBukkit
+                // Folia start - region threading
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(passenger)) {
+                    // removed from region while ticking
+                    return;
+                }
+                if (passenger.doPortalLogic()) {
+                    // portalled
+                    return;
+                }
+                // Folia end - region threading
                 } else {
                     passenger.setDeltaMovement(Vec3.ZERO);
                     passenger.inactiveTick();
@@ -1536,20 +1677,22 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
         } else if (close) { chunkproviderserver.close(false); } // Paper - rewrite chunk system
 
-        // CraftBukkit start - moved from MinecraftServer.saveChunks
-        ServerLevel worldserver1 = this;
-
-        this.serverLevelData.setWorldBorder(worldserver1.getWorldBorder().createSettings());
-        this.serverLevelData.setCustomBossEvents(this.server.getCustomBossEvents().save());
-        this.convertable.saveDataTag(this.server.registryAccess(), this.serverLevelData, this.server.getPlayerList().getSingleplayerData());
-        // CraftBukkit end
+        // Folia - move into saveLevelData
     }
 
-    private void saveLevelData(boolean async) { // Paper - Write SavedData IO async
+    public void saveLevelData(boolean async) { // Paper - Write SavedData IO async // Folia - public
         if (this.dragonFight != null) {
             this.serverLevelData.setEndDragonFightData(this.dragonFight.saveData()); // CraftBukkit
         }
 
+        // Folia start - moved into saveLevelData
+        ServerLevel worldserver1 = this;
+
+        this.serverLevelData.setWorldBorder(worldserver1.getWorldBorder().createSettings());
+        this.serverLevelData.setCustomBossEvents(this.server.getCustomBossEvents().save());
+        this.convertable.saveDataTag(this.server.registryAccess(), this.serverLevelData, this.server.getPlayerList().getSingleplayerData());
+        // Folia end - moved into saveLevelData
+
         this.getChunkSource().getDataStorage().save(async); // Paper - Write SavedData IO async
     }
 
@@ -1603,6 +1746,19 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return list;
     }
 
+    // Folia start - region threading
+    @Nullable
+    public ServerPlayer getRandomLocalPlayer() {
+        List<ServerPlayer> list = this.getLocalPlayers();
+        list = new java.util.ArrayList<>(list);
+        list.removeIf((ServerPlayer player) -> {
+            return !player.isAlive();
+        });
+
+        return list.isEmpty() ? null : (ServerPlayer) list.get(this.random.nextInt(list.size()));
+    }
+    // Folia end - region threading
+
     @Nullable
     public ServerPlayer getRandomPlayer() {
         List<ServerPlayer> list = this.getPlayers(LivingEntity::isAlive);
@@ -1690,8 +1846,8 @@ public class ServerLevel extends Level implements WorldGenLevel {
         } else {
             if (entity instanceof net.minecraft.world.entity.item.ItemEntity itemEntity && itemEntity.getItem().isEmpty()) return false; // Paper - Prevent empty items from being added
             // Paper start - capture all item additions to the world
-            if (captureDrops != null && entity instanceof net.minecraft.world.entity.item.ItemEntity) {
-                captureDrops.add((net.minecraft.world.entity.item.ItemEntity) entity);
+            if (this.getCurrentWorldData().captureDrops != null && entity instanceof net.minecraft.world.entity.item.ItemEntity) { // Folia - region threading
+                this.getCurrentWorldData().captureDrops.add((net.minecraft.world.entity.item.ItemEntity) entity); // Folia - region threading
                 return true;
             }
             // Paper end - capture all item additions to the world
@@ -1846,7 +2002,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     @Override
     public void sendBlockUpdated(BlockPos pos, BlockState oldState, BlockState newState, int flags) {
-        if (this.isUpdatingNavigations) {
+        if (false && this.isUpdatingNavigations) { // Folia - region threading
             String s = "recursive call to sendBlockUpdated";
 
             Util.logAndPauseIfInIde("recursive call to sendBlockUpdated", new IllegalStateException("recursive call to sendBlockUpdated"));
@@ -1859,7 +2015,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
         if (Shapes.joinIsNotEmpty(voxelshape, voxelshape1, BooleanOp.NOT_SAME)) {
             List<PathNavigation> list = new ObjectArrayList();
-            Iterator iterator = this.navigatingMobs.iterator();
+            Iterator iterator = this.getCurrentWorldData().getNavigatingMobs(); // Folia - region threading
 
             while (iterator.hasNext()) {
                 // CraftBukkit start - fix SPIGOT-6362
@@ -1882,7 +2038,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
             }
 
             try {
-                this.isUpdatingNavigations = true;
+                //this.isUpdatingNavigations = true; // Folia - region threading
                 iterator = list.iterator();
 
                 while (iterator.hasNext()) {
@@ -1891,7 +2047,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     navigationabstract1.recomputePath();
                 }
             } finally {
-                this.isUpdatingNavigations = false;
+                //this.isUpdatingNavigations = false; // Folia - region threading
             }
 
         }
@@ -1900,23 +2056,23 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     @Override
     public void updateNeighborsAt(BlockPos pos, Block sourceBlock) {
-        if (captureBlockStates) { return; } // Paper - Cancel all physics during placement
-        this.neighborUpdater.updateNeighborsAtExceptFromFacing(pos, sourceBlock, (Direction) null);
+        if (this.getCurrentWorldData().captureBlockStates) { return; } // Paper - Cancel all physics during placement // Folia - region threading
+        this.getCurrentWorldData().neighborUpdater.updateNeighborsAtExceptFromFacing(pos, sourceBlock, (Direction) null); // Folia - region threading
     }
 
     @Override
     public void updateNeighborsAtExceptFromFacing(BlockPos pos, Block sourceBlock, Direction direction) {
-        this.neighborUpdater.updateNeighborsAtExceptFromFacing(pos, sourceBlock, direction);
+        this.getCurrentWorldData().neighborUpdater.updateNeighborsAtExceptFromFacing(pos, sourceBlock, direction); // Folia - region threading
     }
 
     @Override
     public void neighborChanged(BlockPos pos, Block sourceBlock, BlockPos sourcePos) {
-        this.neighborUpdater.neighborChanged(pos, sourceBlock, sourcePos);
+        this.getCurrentWorldData().neighborUpdater.neighborChanged(pos, sourceBlock, sourcePos); // Folia - region threading
     }
 
     @Override
     public void neighborChanged(BlockState state, BlockPos pos, Block sourceBlock, BlockPos sourcePos, boolean notify) {
-        this.neighborUpdater.neighborChanged(state, pos, sourceBlock, sourcePos, notify);
+        this.getCurrentWorldData().neighborUpdater.neighborChanged(state, pos, sourceBlock, sourcePos, notify); // Folia - region threading
     }
 
     @Override
@@ -1947,7 +2103,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
             explosion.clearToBlow();
         }
 
-        Iterator iterator = this.players.iterator();
+        Iterator iterator = this.getLocalPlayers().iterator(); // Folia - region thraeding
 
         while (iterator.hasNext()) {
             ServerPlayer entityplayer = (ServerPlayer) iterator.next();
@@ -1962,25 +2118,28 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     @Override
     public void blockEvent(BlockPos pos, Block block, int type, int data) {
-        this.blockEvents.add(new BlockEventData(pos, block, type, data));
+        this.getCurrentWorldData().pushBlockEvent(new BlockEventData(pos, block, type, data)); // Folia - regionised ticking
     }
 
     private void runBlockEvents() {
-        this.blockEventsToReschedule.clear();
+        List<BlockEventData> blockEventsToReschedule = new ArrayList<>(64); // Folia - regionised ticking
 
-        while (!this.blockEvents.isEmpty()) {
-            BlockEventData blockactiondata = (BlockEventData) this.blockEvents.removeFirst();
+        // Folia start - regionised ticking
+        io.papermc.paper.threadedregions.RegionizedWorldData worldRegionData = this.getCurrentWorldData();
+        BlockEventData blockactiondata;
+        while ((blockactiondata = worldRegionData.removeFirstBlockEvent()) != null) {
+            // Folia end - regionised ticking
 
             if (this.shouldTickBlocksAt(blockactiondata.pos())) {
                 if (this.doBlockEvent(blockactiondata)) {
                     this.server.getPlayerList().broadcast((Player) null, (double) blockactiondata.pos().getX(), (double) blockactiondata.pos().getY(), (double) blockactiondata.pos().getZ(), 64.0D, this.dimension(), new ClientboundBlockEventPacket(blockactiondata.pos(), blockactiondata.block(), blockactiondata.paramA(), blockactiondata.paramB()));
                 }
             } else {
-                this.blockEventsToReschedule.add(blockactiondata);
+                blockEventsToReschedule.add(blockactiondata); // Folia - regionised ticking
             }
         }
 
-        this.blockEvents.addAll(this.blockEventsToReschedule);
+        worldRegionData.pushBlockEvents(blockEventsToReschedule); // Folia - regionised ticking
     }
 
     private boolean doBlockEvent(BlockEventData event) {
@@ -1991,12 +2150,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     @Override
     public LevelTicks<Block> getBlockTicks() {
-        return this.blockTicks;
+        return this.getCurrentWorldData().getBlockLevelTicks(); // Folia - region ticking
     }
 
     @Override
     public LevelTicks<Fluid> getFluidTicks() {
-        return this.fluidTicks;
+        return this.getCurrentWorldData().getFluidLevelTicks(); // Folia - region ticking
     }
 
     @Nonnull
@@ -2020,7 +2179,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     public <T extends ParticleOptions> int sendParticles(ServerPlayer sender, T t0, double d0, double d1, double d2, int i, double d3, double d4, double d5, double d6, boolean force) {
         // Paper start - Particle API
-        return sendParticles(players, sender, t0, d0, d1, d2, i, d3, d4, d5, d6, force);
+        return sendParticles(this.getLocalPlayers(), sender, t0, d0, d1, d2, i, d3, d4, d5, d6, force); // Folia - region threading
     }
     public <T extends ParticleOptions> int sendParticles(List<ServerPlayer> receivers, @Nullable ServerPlayer sender, T t0, double d0, double d1, double d2, int i, double d3, double d4, double d5, double d6, boolean force) {
         // Paper end - Particle API
@@ -2073,7 +2232,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
     public Entity getEntityOrPart(int id) {
         Entity entity = (Entity) this.getEntities().get(id);
 
-        return entity != null ? entity : (Entity) this.dragonParts.get(id);
+        // Folia start - region threading
+        if (entity !=  null) {
+            return entity;
+        }
+        synchronized (this.dragonParts) {
+            return this.dragonParts.get(id);
+        }
+        // Folia end - region threading
     }
 
     @Nullable
@@ -2128,6 +2294,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         // Paper start - Call missing map initialize event and set id
         final DimensionDataStorage storage = this.getServer().overworld().getDataStorage();
 
+        synchronized (storage.cache) { // Folia - region threading
         final net.minecraft.world.level.saveddata.SavedData existing = storage.cache.get(id);
         if (existing == null && !storage.cache.containsKey(id)) {
             final net.minecraft.world.level.saveddata.SavedData.Factory<MapItemSavedData> factory = MapItemSavedData.factory();
@@ -2143,6 +2310,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         }
 
         return existing instanceof MapItemSavedData data ? data : null;
+        } // Folia - region threading
         // Paper end - Call missing map initialize event and set id
     }
 
@@ -2251,6 +2419,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public boolean setChunkForced(int x, int z, boolean forced) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify force loaded chunks off of the global region"); // Folia - region threading
         ForcedChunksSavedData forcedchunk = (ForcedChunksSavedData) this.getDataStorage().computeIfAbsent(ForcedChunksSavedData.factory(), "chunks");
         ChunkPos chunkcoordintpair = new ChunkPos(x, z);
         long k = chunkcoordintpair.toLong();
@@ -2259,7 +2428,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         if (forced) {
             flag1 = forcedchunk.getChunks().add(k);
             if (flag1) {
-                this.getChunk(x, z);
+                //this.getChunk(x, z); // Folia - region threading - we must let the chunk load asynchronously
             }
         } else {
             flag1 = forcedchunk.getChunks().remove(k);
@@ -2287,13 +2456,18 @@ public class ServerLevel extends Level implements WorldGenLevel {
             BlockPos blockposition1 = pos.immutable();
 
             optional.ifPresent((holder) -> {
-                this.getServer().execute(() -> {
+                Runnable run = () -> { // Folia - region threading
                     this.getPoiManager().remove(blockposition1);
                     DebugPackets.sendPoiRemovedPacket(this, blockposition1);
-                });
+                }; // Folia - region threading
+                // Folia start - region threading
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueChunkTask(
+                    this, blockposition1.getX() >> 4, blockposition1.getZ() >> 4, run
+                );
+                // Folia end - region threading
             });
             optional1.ifPresent((holder) -> {
-                this.getServer().execute(() -> {
+                Runnable run = () -> { // Folia - region threading
                     // Paper start - Remove stale POIs
                     if (optional.isEmpty() && this.getPoiManager().exists(blockposition1, poiType -> true)) {
                         this.getPoiManager().remove(blockposition1);
@@ -2301,7 +2475,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     // Paper end - Remove stale POIs
                     this.getPoiManager().add(blockposition1, holder);
                     DebugPackets.sendPoiAddedPacket(this, blockposition1);
-                });
+                }; // Folia - region threading
+                // Folia start - region threading
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueChunkTask(
+                    this, blockposition1.getX() >> 4, blockposition1.getZ() >> 4, run
+                );
+                // Folia end - region threading
             });
         }
     }
@@ -2348,7 +2527,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         BufferedWriter bufferedwriter = Files.newBufferedWriter(path.resolve("stats.txt"));
 
         try {
-            bufferedwriter.write(String.format(Locale.ROOT, "spawning_chunks: %d\n", playerchunkmap.getDistanceManager().getNaturalSpawnChunkCount()));
+            //bufferedwriter.write(String.format(Locale.ROOT, "spawning_chunks: %d\n", playerchunkmap.getDistanceManager().getNaturalSpawnChunkCount())); // Folia - region threading
             NaturalSpawner.SpawnState spawnercreature_d = this.getChunkSource().getLastSpawnState();
 
             if (spawnercreature_d != null) {
@@ -2362,7 +2541,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
             }
 
             bufferedwriter.write(String.format(Locale.ROOT, "entities: %s\n", this.entityLookup.getDebugInfo())); // Paper - rewrite chunk system
-            bufferedwriter.write(String.format(Locale.ROOT, "block_entity_tickers: %d\n", this.blockEntityTickers.size()));
+            //bufferedwriter.write(String.format(Locale.ROOT, "block_entity_tickers: %d\n", this.blockEntityTickers.size())); // Folia - region threading
             bufferedwriter.write(String.format(Locale.ROOT, "block_ticks: %d\n", this.getBlockTicks().count()));
             bufferedwriter.write(String.format(Locale.ROOT, "fluid_ticks: %d\n", this.getFluidTicks().count()));
             bufferedwriter.write("distance_manager: " + playerchunkmap.getDistanceManager().getDebugStatus() + "\n");
@@ -2508,7 +2687,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     private void dumpBlockEntityTickers(Writer writer) throws IOException {
         CsvOutput csvwriter = CsvOutput.builder().addColumn("x").addColumn("y").addColumn("z").addColumn("type").build(writer);
-        Iterator iterator = this.blockEntityTickers.iterator();
+        Iterator iterator = null; // Folia - region threading
 
         while (iterator.hasNext()) {
             TickingBlockEntity tickingblockentity = (TickingBlockEntity) iterator.next();
@@ -2521,7 +2700,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     @VisibleForTesting
     public void clearBlockEvents(BoundingBox box) {
-        this.blockEvents.removeIf((blockactiondata) -> {
+        this.getCurrentWorldData().removeIfBlockEvents((blockactiondata) -> { // Folia - regionised ticking
             return box.isInside(blockactiondata.pos());
         });
     }
@@ -2530,7 +2709,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     public void blockUpdated(BlockPos pos, Block block) {
         if (!this.isDebug()) {
             // CraftBukkit start
-            if (this.populating) {
+            if (this.getCurrentWorldData().populating) { // Folia - region threading
                 return;
             }
             // CraftBukkit end
@@ -2573,9 +2752,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     @VisibleForTesting
     public String getWatchdogStats() {
-        return String.format(Locale.ROOT, "players: %s, entities: %s [%s], block_entities: %d [%s], block_ticks: %d, fluid_ticks: %d, chunk_source: %s", this.players.size(), this.entityLookup.getDebugInfo(), ServerLevel.getTypeCount(this.entityLookup.getAll(), (entity) -> { // Paper - rewrite chunk system
-            return BuiltInRegistries.ENTITY_TYPE.getKey(entity.getType()).toString();
-        }), this.blockEntityTickers.size(), ServerLevel.getTypeCount(this.blockEntityTickers, TickingBlockEntity::getType), this.getBlockTicks().count(), this.getFluidTicks().count(), this.gatherChunkSourceStats());
+        return "region threading"; // Folia - region threading
     }
 
     private static <T> String getTypeCount(Iterable<T> items, Function<T, String> classifier) {
@@ -2608,6 +2785,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
     public static void makeObsidianPlatform(ServerLevel worldserver, Entity entity) {
         // CraftBukkit end
         BlockPos blockposition = ServerLevel.END_SPAWN_POINT;
+        // Folia start - region threading
+        makeObsidianPlatform(worldserver, entity, blockposition);
+    }
+
+    public static void makeObsidianPlatform(ServerLevel worldserver, Entity entity, BlockPos blockposition) {
+        // Folia end - region threading
         int i = blockposition.getX();
         int j = blockposition.getY() - 2;
         int k = blockposition.getZ();
@@ -2620,11 +2803,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         BlockPos.betweenClosed(i - 2, j, k - 2, i + 2, j, k + 2).forEach((blockposition1) -> {
             blockList.setBlock(blockposition1, Blocks.OBSIDIAN.defaultBlockState(), 3);
         });
-        org.bukkit.World bworld = worldserver.getWorld();
-        org.bukkit.event.world.PortalCreateEvent portalEvent = new org.bukkit.event.world.PortalCreateEvent((List<org.bukkit.block.BlockState>) (List) blockList.getList(), bworld, (entity == null) ? null : entity.getBukkitEntity(), org.bukkit.event.world.PortalCreateEvent.CreateReason.END_PLATFORM);
-
-        worldserver.getCraftServer().getPluginManager().callEvent(portalEvent);
-        if (!portalEvent.isCancelled()) {
+        if (true) { // Folia - region threading
             blockList.updateList();
         }
         // CraftBukkit end
@@ -2645,13 +2824,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public void startTickingChunk(LevelChunk chunk) {
-        chunk.unpackTicks(this.getLevelData().getGameTime());
+        chunk.unpackTicks(this.getRedstoneGameTime()); // Folia - region threading
     }
 
     public void onStructureStartsAvailable(ChunkAccess chunk) {
-        this.server.execute(() -> {
-            this.structureCheck.onStructureLoad(chunk.getPos(), chunk.getAllStarts());
-        });
+        // Folia start - region threading
+        // no longer needs to be on main
+        this.structureCheck.onStructureLoad(chunk.getPos(), chunk.getAllStarts());
+        // Folia end - region threading
     }
 
     @Override
@@ -2673,7 +2853,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         // Paper end - rewrite chunk system
     }
 
-    private boolean isPositionTickingWithEntitiesLoaded(long chunkPos) {
+    public boolean isPositionTickingWithEntitiesLoaded(long chunkPos) { // Folia - region threaded - make public
         // Paper start - optimize is ticking ready type functions
         io.papermc.paper.chunk.system.scheduling.NewChunkHolder chunkHolder = this.chunkTaskScheduler.chunkHolderManager.getChunkHolder(chunkPos);
         // isTicking implies the chunk is loaded, and the chunk is loaded now implies the entities are loaded
@@ -2728,7 +2908,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     // Paper start - optimize redstone (Alternate Current)
     @Override
     public alternate.current.wire.WireHandler getWireHandler() {
-        return wireHandler;
+        return this.getCurrentWorldData().wireHandler; // Folia - region threading - move to regionised data
     }
     // Paper end - optimize redstone (Alternate Current)
 
@@ -2739,16 +2919,16 @@ public class ServerLevel extends Level implements WorldGenLevel {
         public void onCreated(Entity entity) {}
 
         public void onDestroyed(Entity entity) {
-            ServerLevel.this.getScoreboard().entityRemoved(entity);
+            // ServerLevel.this.getScoreboard().entityRemoved(entity); // Folia - region threading
         }
 
         public void onTickingStart(Entity entity) {
             if (entity instanceof net.minecraft.world.entity.Marker && !paperConfig().entities.markers.tick) return; // Paper - Configurable marker ticking
-            ServerLevel.this.entityTickList.add(entity);
+            ServerLevel.this.getCurrentWorldData().addEntityTickingEntity(entity); // Folia - region threading
         }
 
         public void onTickingEnd(Entity entity) {
-            ServerLevel.this.entityTickList.remove(entity);
+            ServerLevel.this.getCurrentWorldData().removeEntityTickingEntity(entity); // Folia - region threading
             // Paper start - Reset pearls when they stop being ticked
             if (paperConfig().fixes.disableUnloadedChunkEnderpearlExploit && entity instanceof net.minecraft.world.entity.projectile.ThrownEnderpearl pearl) {
                 pearl.cachedOwner = null;
@@ -2759,6 +2939,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
         public void onTrackingStart(Entity entity) {
             org.spigotmc.AsyncCatcher.catchOp("entity register"); // Spigot
+            ServerLevel.this.getCurrentWorldData().addLoadedEntity(entity); // Folia - region threading
             // ServerLevel.this.getChunkSource().addEntity(entity); // Paper - ignore and warn about illegal addEntity calls instead of crashing server; moved down below valid=true
             if (entity instanceof ServerPlayer) {
                 ServerPlayer entityplayer = (ServerPlayer) entity;
@@ -2776,7 +2957,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     Util.logAndPauseIfInIde("onTrackingStart called during navigation iteration", new IllegalStateException("onTrackingStart called during navigation iteration"));
                 }
 
-                ServerLevel.this.navigatingMobs.add(entityinsentient);
+                ServerLevel.this.getCurrentWorldData().addNavigatingMob(entityinsentient); // Folia - region threading
             }
 
             if (entity instanceof EnderDragon) {
@@ -2787,7 +2968,9 @@ public class ServerLevel extends Level implements WorldGenLevel {
                 for (int j = 0; j < i; ++j) {
                     EnderDragonPart entitycomplexpart = aentitycomplexpart[j];
 
+                    synchronized (ServerLevel.this.dragonParts) { // Folia - region threading
                     ServerLevel.this.dragonParts.put(entitycomplexpart.getId(), entitycomplexpart);
+                    } // Folia - region threading
                 }
             }
 
@@ -2809,16 +2992,24 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
         public void onTrackingEnd(Entity entity) {
             org.spigotmc.AsyncCatcher.catchOp("entity unregister"); // Spigot
+            ServerLevel.this.getCurrentWorldData().removeLoadedEntity(entity);
             // Spigot start
             if ( entity instanceof Player )
             {
                 com.google.common.collect.Streams.stream( ServerLevel.this.getServer().getAllLevels() ).map( ServerLevel::getDataStorage ).forEach( (worldData) ->
                 {
-                    for (Object o : worldData.cache.values() )
+                    // Folia start - make map data thread-safe
+                    List<Object> worldDataCache;
+                    synchronized (worldData.cache) {
+                        worldDataCache = new java.util.ArrayList<>(worldData.cache.values());
+                    }
+                    for (Object o : worldDataCache )
+                    // Folia end - make map data thread-safe
                     {
                         if ( o instanceof MapItemSavedData )
                         {
                             MapItemSavedData map = (MapItemSavedData) o;
+                            synchronized (map) { // Folia - make map data thread-safe
                             map.carriedByPlayers.remove( (Player) entity );
                             for ( Iterator<MapItemSavedData.HoldingPlayer> iter = (Iterator<MapItemSavedData.HoldingPlayer>) map.carriedBy.iterator(); iter.hasNext(); )
                             {
@@ -2828,6 +3019,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                                     iter.remove();
                                 }
                             }
+                            } // Folia - make map data thread-safe
                         }
                     }
                 } );
@@ -2862,7 +3054,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     Util.logAndPauseIfInIde("onTrackingStart called during navigation iteration", new IllegalStateException("onTrackingStart called during navigation iteration"));
                 }
 
-                ServerLevel.this.navigatingMobs.remove(entityinsentient);
+                ServerLevel.this.getCurrentWorldData().removeNavigatingMob(entityinsentient); // Folia - region threading
             }
 
             if (entity instanceof EnderDragon) {
@@ -2873,13 +3065,16 @@ public class ServerLevel extends Level implements WorldGenLevel {
                 for (int j = 0; j < i; ++j) {
                     EnderDragonPart entitycomplexpart = aentitycomplexpart[j];
 
+                    synchronized (ServerLevel.this.dragonParts) { // Folia - region threading
                     ServerLevel.this.dragonParts.remove(entitycomplexpart.getId());
+                    } // Folia - region threading
                 }
             }
 
             entity.updateDynamicGameEventListener(DynamicGameEventListener::remove);
             // CraftBukkit start
             entity.valid = false;
+            // Folia - region threading - TODO THIS SHIT
             if (!(entity instanceof ServerPlayer)) {
                 for (ServerPlayer player : ServerLevel.this.players) {
                     player.getBukkitEntity().onEntityRemove(entity);
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index b3781efbd3edcf102fe1bda5d6149915dc1127c6..36d074d1abed62b09ca808dc2774bc83a6fd5df7 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -191,7 +191,7 @@ import org.bukkit.inventory.MainHand;
 public class ServerPlayer extends Player {
 
     private static final Logger LOGGER = LogUtils.getLogger();
-    public long lastSave = MinecraftServer.currentTick; // Paper - Incremental chunk and player saving
+    public long lastSave = Long.MIN_VALUE; // Paper // Folia - threaded regions - changed to nanoTime
     private static final int NEUTRAL_MOB_DEATH_NOTIFICATION_RADII_XZ = 32;
     private static final int NEUTRAL_MOB_DEATH_NOTIFICATION_RADII_Y = 10;
     private static final int FLY_STAT_RECORDING_SPEED = 25;
@@ -470,51 +470,151 @@ public class ServerPlayer extends Player {
     }
     // CraftBukkit end
 
-    public void fudgeSpawnLocation(ServerLevel world) {
-        BlockPos blockposition = world.getSharedSpawnPos();
+    // Folia start - region threading
+    private static final int SPAWN_RADIUS_SELECTION_SEARCH = 5;
 
-        if (world.dimensionType().hasSkyLight() && world.serverLevelData.getGameType() != GameType.ADVENTURE) { // CraftBukkit
-            int i = Math.max(0, this.server.getSpawnRadius(world));
-            int j = Mth.floor(world.getWorldBorder().getDistanceToBorder((double) blockposition.getX(), (double) blockposition.getZ()));
+    private static BlockPos getRandomSpawn(ServerLevel world, RandomSource random) {
+        BlockPos spawn = world.getSharedSpawnPos();
+        double radius = (double)Math.max(0, world.getGameRules().getInt(GameRules.RULE_SPAWN_RADIUS));
 
-            if (j < i) {
-                i = j;
-            }
+        double spawnX = (double)spawn.getX() + 0.5;
+        double spawnZ = (double)spawn.getZ() + 0.5;
 
-            if (j <= 1) {
-                i = 1;
+        WorldBorder worldBorder = world.getWorldBorder();
+
+        double selectMinX = Math.max(worldBorder.getMinX() + 1.0, spawnX - radius);
+        double selectMinZ = Math.max(worldBorder.getMinZ() + 1.0, spawnZ - radius);
+        double selectMaxX = Math.min(worldBorder.getMaxX() - 1.0, spawnX + radius);
+        double selectMaxZ = Math.min(worldBorder.getMaxZ() - 1.0, spawnZ + radius);
+
+        double amountX = selectMaxX - selectMinX;
+        double amountZ = selectMaxZ - selectMinZ;
+
+        int selectX = amountX < 1.0 ? Mth.floor(worldBorder.getCenterX()) : (int)Mth.floor((amountX + 1.0) * random.nextDouble() + selectMinX);
+        int selectZ = amountZ < 1.0 ? Mth.floor(worldBorder.getCenterZ()) : (int)Mth.floor((amountZ + 1.0) * random.nextDouble() + selectMinZ);
+
+        return new BlockPos(selectX, 0, selectZ);
+    }
+
+    private static void completeSpawn(ServerLevel world, BlockPos selected,
+                                      ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) {
+        toComplete.complete(io.papermc.paper.util.MCUtil.toLocation(world, Vec3.atBottomCenterOf(selected), world.levelData.getSpawnAngle(), 0.0f));
+    }
+
+    private static BlockPos findSpawnAround(ServerLevel world, ServerPlayer player, BlockPos selected) {
+        // try hard to find, so that we don't attempt another chunk load
+        for (int dz = -SPAWN_RADIUS_SELECTION_SEARCH; dz <= SPAWN_RADIUS_SELECTION_SEARCH; ++dz) {
+            for (int dx = -SPAWN_RADIUS_SELECTION_SEARCH; dx <= SPAWN_RADIUS_SELECTION_SEARCH; ++dx) {
+                BlockPos inChunk = PlayerRespawnLogic.getOverworldRespawnPos(world, selected.getX(), selected.getZ());
+                if (inChunk == null) {
+                    continue;
+                }
+
+                AABB checkVolume = player.getBoundingBoxAt((double)inChunk.getX() + 0.5, (double)inChunk.getY(), (double)inChunk.getZ() + 0.5);
+
+                if (!world.noCollision(player, checkVolume, true)) {
+                    continue;
+                }
+
+                return inChunk;
             }
+        }
 
-            long k = (long) (i * 2 + 1);
-            long l = k * k;
-            int i1 = l > 2147483647L ? Integer.MAX_VALUE : (int) l;
-            int j1 = this.getCoprime(i1);
-            int k1 = RandomSource.create().nextInt(i1);
+        return null;
+    }
 
-            for (int l1 = 0; l1 < i1; ++l1) {
-                int i2 = (k1 + j1 * l1) % i1;
-                int j2 = i2 % (i * 2 + 1);
-                int k2 = i2 / (i * 2 + 1);
-                BlockPos blockposition1 = PlayerRespawnLogic.getOverworldRespawnPos(world, blockposition.getX() + j2 - i, blockposition.getZ() + k2 - i);
+    // rets false when another attempt is required
+    private static boolean trySpawnOrSchedule(ServerLevel world, ServerPlayer player, RandomSource random, int[] attemptCount, int maxAttempts,
+                                              ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) {
+        ++attemptCount[0];
 
-                if (blockposition1 != null) {
-                    this.moveTo(blockposition1, world.getSharedSpawnAngle(), 0.0F); // Paper - MC-200092 - fix first spawn pos yaw being ignored
-                    if (world.noCollision(this, this.getBoundingBox(), true)) { // Paper - make sure this loads chunks, we default to NOT loading now
-                        break;
+        BlockPos rough = getRandomSpawn(world, random);
+
+        int minX = (rough.getX() - SPAWN_RADIUS_SELECTION_SEARCH) >> 4;
+        int minZ = (rough.getZ() - SPAWN_RADIUS_SELECTION_SEARCH) >> 4;
+        int maxX = (rough.getX() + SPAWN_RADIUS_SELECTION_SEARCH) >> 4;
+        int maxZ = (rough.getZ() + SPAWN_RADIUS_SELECTION_SEARCH) >> 4;
+
+        // we could short circuit this check, but it would possibly recurse. Then, it could end up causing a stack overflow
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(world, minX, minZ, maxX, maxZ) || !world.isAreaLoaded(minX, minZ, maxX, maxZ)) {
+            world.loadChunksAsync(minX, maxX, minZ, maxZ,
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                (unused) -> {
+                    BlockPos selected = findSpawnAround(world, player, rough);
+                    if (selected == null) {
+                        // run more spawn attempts
+                        selectSpawn(world, player, random, attemptCount, maxAttempts, toComplete);
+                        return;
                     }
+
+                    completeSpawn(world, selected, toComplete);
+                    return;
                 }
-            }
-        } else {
-            this.moveTo(blockposition, world.getSharedSpawnAngle(), 0.0F); // Paper - MC-200092 - fix first spawn pos yaw being ignored
+            );
+            return true;
+        }
 
-            while (!world.noCollision(this, this.getBoundingBox(), true) && this.getY() < (double) (world.getMaxBuildHeight() - 1)) { // Paper - make sure this loads chunks, we default to NOT loading now
-                this.setPos(this.getX(), this.getY() + 1.0D, this.getZ());
+        BlockPos selected = findSpawnAround(world, player, rough);
+        if (selected == null) {
+            return false;
+        }
+
+        completeSpawn(world, selected, toComplete);
+        return true;
+    }
+
+    private static void selectSpawn(ServerLevel world, ServerPlayer player, RandomSource random, int[] attemptCount, int maxAttempts,
+                                    ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) {
+        do {
+            if (attemptCount[0] >= maxAttempts) {
+                BlockPos sharedSpawn = world.getSharedSpawnPos();
+                BlockPos selected = world.getWorldBorder().clampToBounds((double)sharedSpawn.getX(), (double)sharedSpawn.getY(), (double)sharedSpawn.getZ());
+
+                LOGGER.warn("Found no spawn in radius for player '" + player.getName() + "', ignoring radius");
+
+                // this call requires to return a location with loaded chunks, so we need to schedule a load here
+                io.papermc.paper.chunk.system.ChunkSystem.scheduleChunkLoad(
+                    world, selected.getX() >> 4, selected.getZ() >> 4, net.minecraft.world.level.chunk.ChunkStatus.FULL,
+                    true, ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                    (unused) -> {
+                        completeSpawn(world, selected, toComplete);
+                    }
+                );
+                return;
             }
+        } while (!trySpawnOrSchedule(world, player, random, attemptCount, maxAttempts, toComplete));
+    }
+    // Folia end - region threading
+
+    public static void fudgeSpawnLocation(ServerLevel world, ServerPlayer player, ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) { // Folia - region threading
+        BlockPos blockposition = world.getSharedSpawnPos();
+
+        if (world.dimensionType().hasSkyLight() && world.serverLevelData.getGameType() != GameType.ADVENTURE) { // CraftBukkit
+            // Folia start - region threading
+            selectSpawn(world, player, player.random, new int[1], 500, toComplete);
+            // Folia end - region threading
+        } else {
+            // Folia start - region threading
+            world.loadChunksForMoveAsync(player.getBoundingBoxAt(blockposition.getX() + 0.5, blockposition.getY(), blockposition.getZ() + 0.5),
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                (c) -> {
+                    BlockPos ret = blockposition;
+                    while (!world.noCollision(player, player.getBoundingBoxAt(ret.getX() + 0.5, ret.getY(), ret.getZ() + 0.5), true) && ret.getY() < (double) (world.getMaxBuildHeight() - 1)) { // Paper - make sure this loads chunks, we default to NOT loading now
+                        ret = ret.above();
+                    }
+                    toComplete.complete(io.papermc.paper.util.MCUtil.toLocation(world, Vec3.atBottomCenterOf(ret), world.levelData.getSpawnAngle(), 0.0f));
+                }
+            );
+            // Folia end - region threading
         }
 
     }
 
-    private int getCoprime(int horizontalSpawnArea) {
+    // Folia start - region threading
+    public final java.util.Set<java.util.UUID> pendingTpas = java.util.concurrent.ConcurrentHashMap.newKeySet();
+    // Folia end - region threading
+
+    private static int getCoprime(int horizontalSpawnArea) { // Folia - region threading - not static
         return horizontalSpawnArea <= 16 ? horizontalSpawnArea - 1 : 17;
     }
 
@@ -1169,6 +1269,337 @@ public class ServerPlayer extends Player {
         }
     }
 
+    // Folia start - region threading
+    /**
+     * Teleport flag indicating that the player is to be respawned, expected to only be used
+     * internally for {@link #respawn(java.util.function.Consumer)}.
+     */
+    public static final long TELEPORT_FLAGS_PLAYER_RESPAWN    = Long.MIN_VALUE >>> 0;
+    /**
+     * Teleport flag indicating the player should be placed at the highest y-value that
+     * provides no collisions for the player's bounding box. Note that this setting
+     * does not imply {@link Entity#TELEPORT_FLAG_LOAD_CHUNK}, so it may
+     * sync load chunks unless the load chunk flag is provided.
+     */
+    public static final long TELEPORT_FLAGS_AVOID_SUFFOCATION = Long.MIN_VALUE >>> 1;
+
+    private void avoidSuffocation() {
+        while (!this.level().noCollision(this, this.getBoundingBox(), true) && this.getY() < (double)this.level().getMaxBuildHeight()) { // Folia - make sure this loads chunks, we default to NOT loading now
+            this.setPos(this.getX(), this.getY() + 1.0D, this.getZ());
+        }
+    }
+
+    public void exitEndCredits() {
+        if (!this.wonGame) {
+            // not in the end credits anymore
+            return;
+        }
+        this.wonGame = false;
+
+        this.respawn((player) -> {
+            CriteriaTriggers.CHANGED_DIMENSION.trigger(player, Level.END, Level.OVERWORLD);
+        }, true);
+    }
+
+    public void respawn(java.util.function.Consumer<ServerPlayer> respawnComplete) {
+        this.respawn(respawnComplete, false);
+    }
+
+    private void respawn(java.util.function.Consumer<ServerPlayer> respawnComplete, boolean alive) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot respawn entity async");
+
+        this.getBukkitEntity(); // force bukkit entity to be created before TPing
+
+        if (alive != this.isAlive()) {
+            throw new IllegalStateException("isAlive expected = " + alive);
+        }
+
+        if (!this.hasNullCallback()) {
+            this.unRide();
+        }
+
+        if (this.isVehicle() || this.isPassenger()) {
+            throw new IllegalStateException("Dead player should not be a vehicle or passenger");
+        }
+
+        ServerLevel origin = this.serverLevel();
+        ServerLevel respawnWorld = this.server.getLevel(this.getRespawnDimension());
+
+        // modified based off PlayerList#respawn
+
+        EntityTreeNode passengerTree = this.makePassengerTree();
+
+        this.isChangingDimension = true;
+        origin.removePlayerImmediately(this, RemovalReason.CHANGED_DIMENSION);
+        // reset player if needed, only after removal from world
+        if (!alive) {
+            ServerPlayer.this.reset();
+        }
+        // must be manually removed from connections, delay until after reset() so that we do not trip any thread checks
+        this.serverLevel().getCurrentWorldData().connections.remove(this.connection.connection);
+
+        BlockPos respawnPos = this.getRespawnPosition();
+        float respawnAngle = this.getRespawnAngle();
+        boolean isRespawnForced = this.isRespawnForced();
+
+        ca.spottedleaf.concurrentutil.completable.Completable<Location> spawnPosComplete =
+            new ca.spottedleaf.concurrentutil.completable.Completable<>();
+        boolean[] usedRespawnAnchor = new boolean[1];
+
+        // set up post spawn location logic
+        spawnPosComplete.addWaiter((spawnLoc, throwable) -> {
+            // update pos and velocity
+            ServerPlayer.this.setPosRaw(spawnLoc.getX(), spawnLoc.getY(), spawnLoc.getZ());
+            ServerPlayer.this.setYRot(spawnLoc.getYaw());
+            ServerPlayer.this.setYHeadRot(spawnLoc.getYaw());
+            ServerPlayer.this.setXRot(spawnLoc.getPitch());
+            ServerPlayer.this.setDeltaMovement(Vec3.ZERO);
+            // placeInAsync will update the world
+
+            this.placeInAsync(
+                origin,
+                // use the load chunk flag just in case the spawn loc isn't loaded, and to ensure the chunks
+                // stay loaded for a bit with the teleport ticket
+                ((CraftWorld)spawnLoc.getWorld()).getHandle(),
+                TELEPORT_FLAG_LOAD_CHUNK | TELEPORT_FLAGS_PLAYER_RESPAWN | TELEPORT_FLAGS_AVOID_SUFFOCATION,
+                passengerTree, // note: we expect this to just be the player, no passengers
+                (entity) -> {
+                    // now the player is in the world, and can receive sound
+                    if (usedRespawnAnchor[0]) {
+                        ServerPlayer.this.connection.send(
+                            new ClientboundSoundPacket(
+                                net.minecraft.sounds.SoundEvents.RESPAWN_ANCHOR_DEPLETE, SoundSource.BLOCKS,
+                                ServerPlayer.this.getX(), ServerPlayer.this.getY(), ServerPlayer.this.getZ(),
+                                1.0F, 1.0F, ServerPlayer.this.serverLevel().getRandom().nextLong()
+                            )
+                        );
+                    }
+                    // now the respawn logic is complete
+
+                    // last, call the function callback
+                    if (respawnComplete != null) {
+                        respawnComplete.accept(ServerPlayer.this);
+                    }
+                }
+            );
+        });
+
+        // find and modify respawn block state
+        if (respawnWorld == null || respawnPos == null) {
+            // default to regular spawn
+            fudgeSpawnLocation(this.server.getLevel(Level.OVERWORLD), this, spawnPosComplete);
+        } else {
+            // load chunk for block
+            // give at least 1 radius of loaded chunks so that we do not sync load anything
+            int radiusBlocks = 16;
+            respawnWorld.loadChunksAsync(respawnPos, radiusBlocks,
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                (chunks) -> {
+                    Vec3 spawnPos = findRespawnPositionAndUseSpawnBlock(
+                        respawnWorld, respawnPos, respawnAngle, isRespawnForced, alive
+                    ).orElse(null);
+                    if (spawnPos == null) {
+                        // no spawn
+                        ServerPlayer.this.connection.send(
+                            new ClientboundGameEventPacket(ClientboundGameEventPacket.NO_RESPAWN_BLOCK_AVAILABLE, 0.0F)
+                        );
+                        ServerPlayer.this.setRespawnPosition(
+                            null, null, 0f, false, false,
+                            com.destroystokyo.paper.event.player.PlayerSetSpawnEvent.Cause.PLAYER_RESPAWN
+                        );
+                        // default to regular spawn
+                        fudgeSpawnLocation(this.server.getLevel(Level.OVERWORLD), this, spawnPosComplete);
+                        return;
+                    }
+
+                    boolean isRespawnAnchor = respawnWorld.getBlockState(respawnPos).is(Blocks.RESPAWN_ANCHOR);
+                    boolean isBed = respawnWorld.getBlockState(respawnPos).is(net.minecraft.tags.BlockTags.BEDS);
+                    usedRespawnAnchor[0] = !alive && isRespawnAnchor;
+
+                    // determine angle
+                    float locAngle;
+                    if (!isBed && !isRespawnAnchor) {
+                        // something else
+                        locAngle = respawnAngle;
+                    } else {
+                        // select angle in direction of the difference applied to respawn pos?
+                        Vec3 vec3d1 = Vec3.atBottomCenterOf(respawnPos).subtract(spawnPos).normalize();
+
+                        locAngle = (float)Mth.wrapDegrees(Mth.atan2(vec3d1.z, vec3d1.x) * 57.2957763671875D - 90.0D);
+                    }
+                    ServerPlayer.this.setRespawnPosition(
+                        respawnWorld.dimension(), respawnPos, respawnAngle, isRespawnForced, false,
+                        com.destroystokyo.paper.event.player.PlayerSetSpawnEvent.Cause.PLAYER_RESPAWN
+                    );
+
+                    // finished now, pass the location on
+                    spawnPosComplete.complete(
+                        io.papermc.paper.util.MCUtil.toLocation(respawnWorld, spawnPos, locAngle, 0.0f)
+                    );
+                    return;
+                }
+            );
+        }
+    }
+
+    @Override
+    protected void teleportSyncSameRegion(Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate) {
+        if (yaw != null) {
+            this.setYRot(yaw.floatValue());
+            this.setYHeadRot(yaw.floatValue());
+        }
+        if (pitch != null) {
+            this.setXRot(pitch.floatValue());
+        }
+        if (speedDirectionUpdate != null) {
+            this.setDeltaMovement(speedDirectionUpdate.normalize().scale(this.getDeltaMovement().length()));
+        }
+        this.connection.internalTeleport(pos.x, pos.y, pos.z, this.getYRot(), this.getXRot(), java.util.Collections.emptySet());
+        this.connection.resetPosition();
+        this.resetStoredPositions();
+    }
+
+    @Override
+    protected ServerPlayer transformForAsyncTeleport(ServerLevel destination, Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate) {
+        // must be manually removed from connections
+        this.serverLevel().getCurrentWorldData().connections.remove(this.connection.connection);
+        this.serverLevel().removePlayerImmediately(this, Entity.RemovalReason.CHANGED_DIMENSION);
+
+        this.spawnIn(destination);
+        this.transform(pos, yaw, pitch, speedDirectionUpdate);
+
+        return this;
+    }
+
+    @Override
+    public void preChangeDimension() {
+        super.preChangeDimension();
+        this.stopUsingItem();
+    }
+
+    @Override
+    protected void placeSingleSync(ServerLevel originWorld, ServerLevel destination, EntityTreeNode treeNode, long teleportFlags) {
+        if (destination == originWorld && (teleportFlags & TELEPORT_FLAGS_PLAYER_RESPAWN) == 0L) {
+            this.unsetRemoved();
+            destination.addDuringTeleport(this);
+
+            // must be manually added to connections
+            this.serverLevel().getCurrentWorldData().connections.add(this.connection.connection);
+
+            if ((teleportFlags & TELEPORT_FLAGS_AVOID_SUFFOCATION) != 0L && treeNode.passengers == null && treeNode.parent == null) {
+                this.avoidSuffocation();
+            }
+
+            // required to set up the pending teleport stuff to the client, and to actually update
+            // the player's position clientside
+            this.connection.internalTeleport(
+                this.getX(), this.getY(), this.getZ(), this.getYRot(), this.getXRot(),
+                java.util.Collections.emptySet()
+            );
+            this.connection.resetPosition();
+
+            this.postChangeDimension();
+        } else {
+            // Modelled after PlayerList#respawn
+
+            // We avoid checking for disconnection here, which means we do not have to add/remove from
+            // the player list here. We can let this be properly handled by the connection handler
+
+            // pre-add logic
+            PlayerList playerlist = this.server.getPlayerList();
+            net.minecraft.world.level.storage.LevelData worlddata = destination.getLevelData();
+            this.connection.send(
+                new ClientboundRespawnPacket(
+                    this.createCommonSpawnInfo(destination),
+                    (teleportFlags & TELEPORT_FLAGS_PLAYER_RESPAWN) == 0L ? (byte)1 : (byte)0
+                )
+            );
+            // don't bother with the chunk cache radius and simulation distance packets, they are handled
+            // by the chunk loader
+            this.spawnIn(destination); // important that destination != null
+            // we can delay teleport until later, the player position is already set up at the target
+            this.setShiftKeyDown(false);
+
+            this.connection.send(new net.minecraft.network.protocol.game.ClientboundSetDefaultSpawnPositionPacket(
+                destination.getSharedSpawnPos(), destination.getSharedSpawnAngle()
+            ));
+            this.connection.send(new ClientboundChangeDifficultyPacket(
+                worlddata.getDifficulty(), worlddata.isDifficultyLocked()
+            ));
+            this.connection.send(new ClientboundSetExperiencePacket(
+                this.experienceProgress, this.totalExperience, this.experienceLevel
+            ));
+
+            playerlist.sendLevelInfo(this, destination);
+            playerlist.sendPlayerPermissionLevel(this);
+
+            // regular world add logic
+            this.unsetRemoved();
+            destination.addDuringTeleport(this);
+
+            // must be manually added to connections
+            this.serverLevel().getCurrentWorldData().connections.add(this.connection.connection);
+
+            if ((teleportFlags & TELEPORT_FLAGS_AVOID_SUFFOCATION) != 0L && treeNode.passengers == null && treeNode.parent == null) {
+                this.avoidSuffocation();
+            }
+
+            // required to set up the pending teleport stuff to the client, and to actually update
+            // the player's position clientside
+            this.connection.internalTeleport(
+                this.getX(), this.getY(), this.getZ(), this.getYRot(), this.getXRot(),
+                java.util.Collections.emptySet()
+            );
+            this.connection.resetPosition();
+
+            // delay callback until after post add logic
+
+            // post add logic
+
+            // "Added from changeDimension"
+            this.setHealth(this.getHealth());
+            playerlist.sendAllPlayerInfo(this);
+            this.onUpdateAbilities();
+            for (MobEffectInstance mobEffect : this.getActiveEffects()) {
+                this.connection.send(new ClientboundUpdateMobEffectPacket(this.getId(), mobEffect));
+            }
+
+            this.triggerDimensionChangeTriggers(originWorld);
+
+            // finished
+
+            this.postChangeDimension();
+        }
+    }
+
+    @Override
+    public boolean endPortalLogicAsync() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot portal entity async");
+
+        if (this.level().getTypeKey() == LevelStem.END) {
+            if (!this.canPortalAsync(false)) {
+                return false;
+            }
+            this.wonGame = true;
+            // TODO is there a better solution to this that DOESN'T skip the credits?
+            this.seenCredits = true;
+            this.connection.send(new ClientboundGameEventPacket(ClientboundGameEventPacket.WIN_GAME, this.seenCredits ? 0.0F : 1.0F));
+            this.exitEndCredits();
+            return true;
+        } else {
+            return super.endPortalLogicAsync();
+        }
+    }
+
+    @Override
+    protected void prePortalLogic(ServerLevel origin, ServerLevel destination, PortalType type) {
+        super.prePortalLogic(origin, destination, type);
+        if (origin.getTypeKey() == LevelStem.OVERWORLD && destination.getTypeKey() == LevelStem.NETHER) {
+            this.enteredNetherPosition = this.position();
+        }
+    }
+    // Folia end - region threading
+
     @Nullable
     @Override
     public Entity changeDimension(ServerLevel destination) {
@@ -1178,6 +1609,11 @@ public class ServerPlayer extends Player {
 
     @Nullable
     public Entity changeDimension(ServerLevel worldserver, PlayerTeleportEvent.TeleportCause cause) {
+        // Folia start - region threading
+        if (true) {
+            throw new UnsupportedOperationException("Must use teleportAsync while in region threading");
+        }
+        // Folia end - region threading
         // CraftBukkit end
         if (this.isSleeping()) return this; // CraftBukkit - SPIGOT-3154
         // this.isChangingDimension = true; // CraftBukkit - Moved down and into PlayerList#changeDimension
@@ -2232,6 +2668,12 @@ public class ServerPlayer extends Player {
     public void setCamera(@Nullable Entity entity) {
         Entity entity1 = this.getCamera();
 
+        // Folia start - region threading
+        if (entity != null && !io.papermc.paper.util.TickThread.isTickThreadFor(entity)) {
+            return;
+        }
+        // Folia end - region threading
+
         this.camera = (Entity) (entity == null ? this : entity);
         if (entity1 != this.camera) {
             // Paper start - Add PlayerStartSpectatingEntityEvent and PlayerStopSpectatingEntity
@@ -2733,7 +3175,7 @@ public class ServerPlayer extends Player {
         this.experienceLevel = this.newLevel;
         this.totalExperience = this.newTotalExp;
         this.experienceProgress = 0;
-        this.deathTime = 0;
+        this.deathTime = 0; this.broadcastedDeath = false; // Folia - region threading
         this.setArrowCount(0, true); // CraftBukkit - ArrowBodyCountChangeEvent
         this.removeAllEffects(org.bukkit.event.entity.EntityPotionEffectEvent.Cause.DEATH);
         this.effectsDirty = true;
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
index a7b217ddbcbf92513bd38101fdfca2075505e267..8d2d0852ca5d137a74ba7be9a58e45c6bb832552 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
@@ -128,7 +128,7 @@ public class ServerPlayerGameMode {
         BlockState iblockdata;
 
         if (this.hasDelayedDestroy) {
-            iblockdata = this.level.getBlockStateIfLoaded(this.delayedDestroyPos); // Paper - Don't allow digging into unloaded chunks
+            iblockdata = !io.papermc.paper.util.TickThread.isTickThreadFor(this.level, this.delayedDestroyPos) ? null : this.level.getBlockStateIfLoaded(this.delayedDestroyPos); // Paper - Don't allow digging into unloaded chunks // Folia - region threading - don't destroy blocks not owned
             if (iblockdata == null || iblockdata.isAir()) { // Paper - Don't allow digging into unloaded chunks
                 this.hasDelayedDestroy = false;
             } else {
@@ -141,7 +141,7 @@ public class ServerPlayerGameMode {
             }
         } else if (this.isDestroyingBlock) {
             // Paper start - Don't allow digging into unloaded chunks; don't want to do same logic as above, return instead
-            iblockdata = this.level.getBlockStateIfLoaded(this.destroyPos);
+            iblockdata = !io.papermc.paper.util.TickThread.isTickThreadFor(this.level, this.destroyPos) ? null : this.level.getBlockStateIfLoaded(this.destroyPos);
             if (iblockdata == null) {
                 this.isDestroyingBlock = false;
                 return;
@@ -416,7 +416,7 @@ public class ServerPlayerGameMode {
             } else {
                 // CraftBukkit start
                 org.bukkit.block.BlockState state = bblock.getState();
-                this.level.captureDrops = new ArrayList<>();
+                this.level.getCurrentWorldData().captureDrops = new ArrayList<>(); // Folia - region threading
                 // CraftBukkit end
                 BlockState iblockdata1 = block.playerWillDestroy(this.level, pos, iblockdata, this.player);
                 boolean flag = this.level.removeBlock(pos, false);
@@ -444,8 +444,8 @@ public class ServerPlayerGameMode {
                     // return true; // CraftBukkit
                 }
                 // CraftBukkit start
-                java.util.List<net.minecraft.world.entity.item.ItemEntity> itemsToDrop = this.level.captureDrops; // Paper - capture all item additions to the world
-                this.level.captureDrops = null; // Paper - capture all item additions to the world; Remove this earlier so that we can actually drop stuff
+                java.util.List<net.minecraft.world.entity.item.ItemEntity> itemsToDrop = this.level.getCurrentWorldData().captureDrops; // Paper - capture all item additions to the world  // Folia - region threading
+                this.level.getCurrentWorldData().captureDrops = null; // Paper - capture all item additions to the world; Remove this earlier so that we can actually drop stuff  // Folia - region threading
                 if (event.isDropItems()) {
                     org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockDropItemEvent(bblock, state, this.player, itemsToDrop); // Paper - capture all item additions to the world
                 }
diff --git a/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java b/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
index 17b624294fc0cab2976e3804e6c9a24b91a0e3aa..7c10a1f9f7bcb1711a05cddabe0cc86258d49a57 100644
--- a/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
+++ b/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
@@ -103,10 +103,15 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
         this.chunkMap.level.chunkTaskScheduler.radiusAwareScheduler.queueInfiniteRadiusTask(() -> { // Paper - rewrite chunk system
             this.theLightEngine.relightChunks(chunks, (ChunkPos chunkPos) -> {
                 chunkLightCallback.accept(chunkPos);
-                ((java.util.concurrent.Executor)((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().mainThreadProcessor).execute(() -> {
+                Runnable run = () -> { // Folia - region threading
                     ((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().chunkMap.getUpdatingChunkIfPresent(chunkPos.toLong()).broadcast(new net.minecraft.network.protocol.game.ClientboundLightUpdatePacket(chunkPos, ThreadedLevelLightEngine.this, null, null), false);
                     ((ServerLevel)this.theLightEngine.getWorld()).getChunkSource().removeTicketAtLevel(TicketType.CHUNK_RELIGHT, chunkPos, io.papermc.paper.util.MCUtil.getTicketLevelFor(ChunkStatus.LIGHT), ticketIds.get(chunkPos));
-                });
+                }; // Folia - region threading
+                // Folia start - region threading
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueChunkTask(
+                    (ServerLevel)this.theLightEngine.getWorld(), chunkPos.x, chunkPos.z, run
+                );
+                // Folia end - region threading
             }, onComplete);
         });
         this.tryScheduleUpdate();
@@ -114,7 +119,7 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
         return totalChunks;
     }
 
-    private final Long2IntOpenHashMap chunksBeingWorkedOn = new Long2IntOpenHashMap();
+    //private final Long2IntOpenHashMap chunksBeingWorkedOn = new Long2IntOpenHashMap(); // Folia - region threading
 
     private void queueTaskForSection(final int chunkX, final int chunkY, final int chunkZ,
                                      final Supplier<io.papermc.paper.chunk.system.light.LightQueue.ChunkTasks> runnable) { // Paper - rewrite chunk system
@@ -134,11 +139,16 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
             return;
         }
 
-        if (!world.getChunkSource().chunkMap.mainThreadExecutor.isSameThread()) {
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(world, chunkX, chunkZ)) { // Folia - region threading
             // ticket logic is not safe to run off-main, re-schedule
-            world.getChunkSource().chunkMap.mainThreadExecutor.execute(() -> {
+            Runnable run = () -> { // Folia - region threading
                 this.queueTaskForSection(chunkX, chunkY, chunkZ, runnable);
-            });
+            }; // Folia - region threading
+            // Folia start - region threading
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                world, chunkX, chunkZ, run
+            );
+            // Folia end - region threading
             return;
         }
 
@@ -157,22 +167,28 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
         }
         updateFuture.isTicketAdded = true;
 
-        final int references = this.chunksBeingWorkedOn.addTo(key, 1);
+        final int references = this.chunkMap.level.getCurrentWorldData().chunksBeingWorkedOn.addTo(key, 1); // Folia - region threading
         if (references == 0) {
             final ChunkPos pos = new ChunkPos(chunkX, chunkZ);
             world.getChunkSource().addRegionTicket(ca.spottedleaf.starlight.common.light.StarLightInterface.CHUNK_WORK_TICKET, pos, 0, pos);
         }
 
-        updateFuture.onComplete.thenAcceptAsync((final Void ignore) -> {
-            final int newReferences = this.chunksBeingWorkedOn.get(key);
-            if (newReferences == 1) {
-                this.chunksBeingWorkedOn.remove(key);
-                final ChunkPos pos = new ChunkPos(chunkX, chunkZ);
-                world.getChunkSource().removeRegionTicket(ca.spottedleaf.starlight.common.light.StarLightInterface.CHUNK_WORK_TICKET, pos, 0, pos);
-            } else {
-                this.chunksBeingWorkedOn.put(key, newReferences - 1);
-            }
-        }, world.getChunkSource().chunkMap.mainThreadExecutor).whenComplete((final Void ignore, final Throwable thr) -> {
+        // Folia start - region threading
+        updateFuture.onComplete.thenAccept((final Void ignore) -> {
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                this.chunkMap.level, chunkX, chunkZ, () -> {
+                    final int newReferences = this.chunkMap.level.getCurrentWorldData().chunksBeingWorkedOn.get(key);
+                    if (newReferences == 1) {
+                        this.chunkMap.level.getCurrentWorldData().chunksBeingWorkedOn.remove(key);
+                        final ChunkPos pos = new ChunkPos(chunkX, chunkZ);
+                        world.getChunkSource().removeRegionTicket(ca.spottedleaf.starlight.common.light.StarLightInterface.CHUNK_WORK_TICKET, pos, 0, pos);
+                    } else {
+                        this.chunkMap.level.getCurrentWorldData().chunksBeingWorkedOn.put(key, newReferences - 1);
+                    }
+                }
+            );
+        }).whenComplete((final Void ignore, final Throwable thr) -> {
+            // Folia end - region threading
             if (thr != null) {
                 LOGGER.error("Failed to remove ticket level for post chunk task " + new ChunkPos(chunkX, chunkZ), thr);
             }
diff --git a/src/main/java/net/minecraft/server/level/TicketType.java b/src/main/java/net/minecraft/server/level/TicketType.java
index 658e63ebde81dc14c8ab5850fb246dc0aab25dea..7e1f15ac8d2f7c86d4aba1be5df717052ffb31f0 100644
--- a/src/main/java/net/minecraft/server/level/TicketType.java
+++ b/src/main/java/net/minecraft/server/level/TicketType.java
@@ -37,6 +37,14 @@ public class TicketType<T> {
     public static final TicketType<Long> NON_FULL_SYNC_LOAD = create("non_full_sync_load", Long::compareTo);
     public static final TicketType<ChunkPos> DELAY_UNLOAD = create("delay_unload", Comparator.comparingLong(ChunkPos::toLong), 1);
     // Paper end - rewrite chunk system
+    // Folia start - region threading
+    public static final TicketType<Unit> LOGIN = create("login", (u1, u2) -> 0, 20);
+    public static final TicketType<Unit> DELAYED = create("delay", (u1, u2) -> 0, 5);
+    public static final TicketType<Long> END_GATEWAY_EXIT_SEARCH = create("end_gateway_exit_search", Long::compareTo);
+    public static final TicketType<Long> NETHER_PORTAL_DOUBLE_CHECK = create("nether_portal_double_check", Long::compareTo);
+    public static final TicketType<Long> TELEPORT_HOLD_TICKET = create("teleport_hold_ticket", Long::compareTo);
+    public static final TicketType<Unit> REGION_SCHEDULER_API_HOLD = create("region_scheduler_api_hold", (a, b) -> 0);
+    // Folia end - region threading
 
     public static <T> TicketType<T> create(String name, Comparator<T> argumentComparator) {
         return new TicketType<>(name, argumentComparator, 0L);
diff --git a/src/main/java/net/minecraft/server/level/WorldGenRegion.java b/src/main/java/net/minecraft/server/level/WorldGenRegion.java
index 9c3f8f79c2b3389a118dce9a1558edda52446833..8c455cda45ca2d724fbc140d53ffc7ecba3ca44c 100644
--- a/src/main/java/net/minecraft/server/level/WorldGenRegion.java
+++ b/src/main/java/net/minecraft/server/level/WorldGenRegion.java
@@ -84,6 +84,13 @@ public class WorldGenRegion implements WorldGenLevel {
     private final AtomicLong subTickCount = new AtomicLong();
     private static final ResourceLocation WORLDGEN_REGION_RANDOM = new ResourceLocation("worldgen_region_random");
 
+    // Folia start - region threading
+    @Override
+    public StructureManager structureManager() {
+        return this.structureManager;
+    }
+    // Folia end - region threading
+
     public WorldGenRegion(ServerLevel world, List<ChunkAccess> chunks, ChunkStatus status, int placementRadius) {
         this.generatingStatus = status;
         this.writeRadiusCutoff = placementRadius;
diff --git a/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
index 0306771b8f90dcdd77f151c19c6c2d75c41f8feb..22f0d91df0a81040d72c499fbff32b3a9d41598f 100644
--- a/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
@@ -75,6 +75,10 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
         // CraftBukkit end
     }
 
+    // Folia start - region threading
+    private boolean handledDisconnect = false;
+    // Folia end - region threading
+
     @Override
     public void onDisconnect(Component reason) {
         // Paper start - Fix kick event leave message not being sent
@@ -82,10 +86,18 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
     }
     public void onDisconnect(Component reason, @Nullable net.kyori.adventure.text.Component quitMessage) {
         // Paper end - Fix kick event leave message not being sent
+        // Folia start - region threading
+        if (this.handledDisconnect) {
+            // avoid retiring scheduler twice
+            return;
+        }
+        this.handledDisconnect = true;
+        // Folia end - region threading
         if (this.isSingleplayerOwner()) {
             ServerCommonPacketListenerImpl.LOGGER.info("Stopping singleplayer server as player logged out");
             this.server.halt(false);
         }
+        this.player.getBukkitEntity().taskScheduler.retire(); // Folia - region threading
 
     }
 
@@ -99,9 +111,9 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
             this.keepAlivePending = false;
         } else if (!this.isSingleplayerOwner()) {
             // Paper start - This needs to be handled on the main thread for plugins
-            server.submit(() -> {
+            // Folia - region threading - do not schedule to main anymore, there is no main
                 this.disconnect(ServerCommonPacketListenerImpl.TIMEOUT_DISCONNECTION_MESSAGE, org.bukkit.event.player.PlayerKickEvent.Cause.TIMEOUT); // Paper - kick event cause
-            });
+            // Folia - region threading - do not schedule to main anymore, there is no main
             // Paper end - This needs to be handled on the main thread for plugins
         }
 
@@ -292,24 +304,8 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
         if (this.processedDisconnect) {
             return;
         }
-        if (!this.cserver.isPrimaryThread()) {
-            Waitable waitable = new Waitable() {
-                @Override
-                protected Object evaluate() {
-                    ServerCommonPacketListenerImpl.this.disconnect(reason, cause); // Paper - adventure
-                    return null;
-                }
-            };
-
-            this.server.processQueue.add(waitable);
-
-            try {
-                waitable.get();
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-            } catch (ExecutionException e) {
-                throw new RuntimeException(e);
-            }
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(this.player)) { // Folia - region threading
+            this.connection.disconnectSafely(io.papermc.paper.adventure.PaperAdventure.asVanilla(reason), cause); // Folia - region threading - it HAS to be delayed/async to avoid deadlock if we try to wait for another region
             return;
         }
 
@@ -340,7 +336,7 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
 
         Objects.requireNonNull(this.connection);
         // CraftBukkit - Don't wait
-        minecraftserver.scheduleOnMain(networkmanager::handleDisconnection); // Paper
+        // Folia - region threading
     }
 
     protected boolean isSingleplayerOwner() {
diff --git a/src/main/java/net/minecraft/server/network/ServerConfigurationPacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerConfigurationPacketListenerImpl.java
index 87c5690774363edc1b7ebff10b041e48c0a6d56d..18113fdd0d3f269e2ffb3b661d6adfa5b20d7386 100644
--- a/src/main/java/net/minecraft/server/network/ServerConfigurationPacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerConfigurationPacketListenerImpl.java
@@ -43,6 +43,7 @@ public class ServerConfigurationPacketListenerImpl extends ServerCommonPacketLis
     @Nullable
     private ConfigurationTask currentTask;
     private ClientInformation clientInformation;
+    public boolean switchToMain = false; // Folia - region threading - rewrite login process
 
     public ServerConfigurationPacketListenerImpl(MinecraftServer minecraftserver, Connection networkmanager, CommonListenerCookie commonlistenercookie, ServerPlayer player) { // CraftBukkit
         super(minecraftserver, networkmanager, commonlistenercookie, player); // CraftBukkit
@@ -131,7 +132,57 @@ public class ServerConfigurationPacketListenerImpl extends ServerCommonPacketLis
 
             ServerPlayer entityplayer = playerlist.getPlayerForLogin(this.gameProfile, this.clientInformation, this.player); // CraftBukkit
 
-            playerlist.placeNewPlayer(this.connection, entityplayer, this.createCookie(this.clientInformation));
+            // Folia start - region threading - rewrite login process
+            io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot handle player login off global tick thread");
+            CommonListenerCookie clientData = this.createCookie(this.clientInformation);
+            org.apache.commons.lang3.mutable.MutableObject<net.minecraft.nbt.CompoundTag> data = new org.apache.commons.lang3.mutable.MutableObject<>();
+            org.apache.commons.lang3.mutable.MutableObject<String> lastKnownName = new org.apache.commons.lang3.mutable.MutableObject<>();
+            ca.spottedleaf.concurrentutil.completable.Completable<org.bukkit.Location> toComplete = new ca.spottedleaf.concurrentutil.completable.Completable<>();
+            // note: need to call addWaiter before completion to ensure the callback is invoked synchronously
+            // the loadSpawnForNewPlayer function always completes the completable once the chunks were loaded,
+            // on the load callback for those chunks (so on the same region)
+            // this guarantees the chunk cannot unload under our feet
+            toComplete.addWaiter((org.bukkit.Location loc, Throwable t) -> {
+                int chunkX = net.minecraft.util.Mth.floor(loc.getX()) >> 4;
+                int chunkZ = net.minecraft.util.Mth.floor(loc.getZ()) >> 4;
+
+                net.minecraft.server.level.ServerLevel world = ((org.bukkit.craftbukkit.CraftWorld)loc.getWorld()).getHandle();
+                // we just need to hold the chunks at loaded until the next tick
+                // so we do not need to care about unique IDs for the ticket
+                world.getChunkSource().addTicketAtLevel(
+                    net.minecraft.server.level.TicketType.LOGIN,
+                    new net.minecraft.world.level.ChunkPos(chunkX, chunkZ),
+                    io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.FULL_LOADED_TICKET_LEVEL,
+                    net.minecraft.util.Unit.INSTANCE
+                );
+
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                    world, chunkX, chunkZ,
+                    () -> {
+                        // once switchToMain is set, the current ticking region now owns the connection and is responsible
+                        // for cleaning it up
+                        playerlist.placeNewPlayer(
+                            ServerConfigurationPacketListenerImpl.this.connection,
+                            entityplayer,
+                            clientData,
+                            data.getValue(),
+                            lastKnownName.getValue(),
+                            loc
+                        );
+                    },
+                    ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER
+                );
+            });
+            this.switchToMain = true;
+            try {
+                // now the connection responsibility is transferred on the region
+                playerlist.loadSpawnForNewPlayer(this.connection, entityplayer, clientData, data, lastKnownName, toComplete);
+            } catch (final Throwable throwable) {
+                // assume toComplete will not be invoked
+                // ensure global tick thread owns the connection again, to properly disconnect it
+                this.switchToMain = false;
+            }
+            // Folia end - region threading - rewrite login process
             this.connection.resumeInboundAfterProtocolChange();
         } catch (Exception exception) {
             ServerConfigurationPacketListenerImpl.LOGGER.error("Couldn't place player in world", exception);
diff --git a/src/main/java/net/minecraft/server/network/ServerConnectionListener.java b/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
index 586521a2cbb1d4dcfb912029f65e4363ec7674a7..6e95017f4c36208abdf344e3b7d55efe2d5b4e10 100644
--- a/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
+++ b/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
@@ -152,10 +152,13 @@ public class ServerConnectionListener {
                         });
                     }
                     // Paper end - Add support for proxy protocol
-                    pending.add(object); // Paper - prevent blocking on adding a new connection while the server is ticking
+                    // Folia - connection fixes - move down
                     ((Connection) object).configurePacketHandler(channelpipeline);
                     ((Connection) object).setListenerForServerboundHandshake(new ServerHandshakePacketListenerImpl(ServerConnectionListener.this.server, (Connection) object));
                     io.papermc.paper.network.ChannelInitializeListenerHolder.callListeners(channel); // Paper - Add Channel initialization listeners
+                    // Folia start - regionised threading
+                    io.papermc.paper.threadedregions.RegionizedServer.getInstance().addConnection(object);
+                    // Folia end - regionised threading
                 }
             }).group(eventloopgroup).localAddress(address)).option(ChannelOption.AUTO_READ, false).bind().syncUninterruptibly()); // CraftBukkit // Paper - Unix domain socket support
         }
@@ -218,7 +221,7 @@ public class ServerConnectionListener {
             // Spigot Start
             this.addPending(); // Paper - prevent blocking on adding a new connection while the server is ticking
             // This prevents players from 'gaming' the server, and strategically relogging to increase their position in the tick order
-            if ( org.spigotmc.SpigotConfig.playerShuffle > 0 && MinecraftServer.currentTick % org.spigotmc.SpigotConfig.playerShuffle == 0 )
+            if ( org.spigotmc.SpigotConfig.playerShuffle > 0 && 0 % org.spigotmc.SpigotConfig.playerShuffle == 0 ) // Folia - region threading
             {
                 Collections.shuffle( this.connections );
             }
diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index fe2ef36ab5dc4b933abf24dbfd0e811c53239cf0..e7b510dee355a9865bd67f5aea52c62957226eb3 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -291,7 +291,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
     private final LastSeenMessagesValidator lastSeenMessages = new LastSeenMessagesValidator(20);
     private final MessageSignatureCache messageSignatureCache = MessageSignatureCache.createDefault();
     private final FutureChain chatMessageChain;
-    private boolean waitingForSwitchToConfig;
+    public volatile boolean waitingForSwitchToConfig; // Folia - rewrite login process - fix bad ordering of this field write + public
     private static final int MAX_SIGN_LINE_LENGTH = Integer.getInteger("Paper.maxSignLength", 80); // Paper - Limit client sign length
 
     public ServerGamePacketListenerImpl(MinecraftServer server, Connection connection, ServerPlayer player, CommonListenerCookie clientData) {
@@ -309,10 +309,10 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
     }
 
     // CraftBukkit start - add fields
-    private int lastTick = MinecraftServer.currentTick;
+    private long lastTick = Util.getMillis() / 50L; // Folia - region threading
     private int allowedPlayerTicks = 1;
-    private int lastDropTick = MinecraftServer.currentTick;
-    private int lastBookTick  = MinecraftServer.currentTick;
+    private long lastDropTick = Util.getMillis() / 50L; // Folia - region threading
+    private long lastBookTick  = Util.getMillis() / 50L; // Folia - region threading
     private int dropCount = 0;
 
     private boolean hasMoved = false;
@@ -324,8 +324,21 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
     private boolean justTeleported = false;
     // CraftBukkit end
 
+    // Folia start - region threading
+    public net.minecraft.world.level.ChunkPos disconnectPos;
+    private static final java.util.concurrent.atomic.AtomicLong DISCONNECT_TICKET_ID_GENERATOR = new java.util.concurrent.atomic.AtomicLong();
+    public static final net.minecraft.server.level.TicketType<Long> DISCONNECT_TICKET = net.minecraft.server.level.TicketType.create("disconnect_ticket", Long::compareTo);
+    public final Long disconnectTicketId = Long.valueOf(DISCONNECT_TICKET_ID_GENERATOR.getAndIncrement());
+    // Folia end - region threading
+
     @Override
     public void tick() {
+        // Folia start - region threading
+        this.keepConnectionAlive();
+        if (this.processedDisconnect || this.player.wonGame) {
+            return;
+        }
+        // Folia end - region threading
         if (this.ackBlockChangesUpTo > -1) {
             this.send(new ClientboundBlockChangedAckPacket(this.ackBlockChangesUpTo));
             this.ackBlockChangesUpTo = -1;
@@ -374,7 +387,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             this.aboveGroundVehicleTickCount = 0;
         }
 
-        this.keepConnectionAlive();
+        // Folia - region threading - moved to beginning of method
         // CraftBukkit start
         for (int spam; (spam = this.chatSpamTickCount.get()) > 0 && !this.chatSpamTickCount.compareAndSet(spam, spam - 1); ) ;
         if (tabSpamLimiter.get() > 0) tabSpamLimiter.getAndDecrement(); // Paper - configurable tab spam limits
@@ -411,6 +424,19 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         this.lastGoodX = this.player.getX();
         this.lastGoodY = this.player.getY();
         this.lastGoodZ = this.player.getZ();
+        // Folia start - support vehicle teleportations
+        this.lastVehicle = this.player.getRootVehicle();
+        if (this.lastVehicle != this.player && this.lastVehicle.getControllingPassenger() == this.player) {
+            this.vehicleFirstGoodX = this.lastVehicle.getX();
+            this.vehicleFirstGoodY = this.lastVehicle.getY();
+            this.vehicleFirstGoodZ = this.lastVehicle.getZ();
+            this.vehicleLastGoodX = this.lastVehicle.getX();
+            this.vehicleLastGoodY = this.lastVehicle.getY();
+            this.vehicleLastGoodZ = this.lastVehicle.getZ();
+        } else {
+            this.lastVehicle = null;
+        }
+        // Folia end - support vehicle teleportations
     }
 
     @Override
@@ -511,9 +537,10 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 // Paper end - fix large move vectors killing the server
 
                 // CraftBukkit start - handle custom speeds and skipped ticks
-                this.allowedPlayerTicks += (System.currentTimeMillis() / 50) - this.lastTick;
+                int currTick = (int)(Util.getMillis() / 50); // Folia - region threading
+                this.allowedPlayerTicks += currTick - this.lastTick; // Folia - region threading
                 this.allowedPlayerTicks = Math.max(this.allowedPlayerTicks, 1);
-                this.lastTick = (int) (System.currentTimeMillis() / 50);
+                this.lastTick = (int) currTick; // Folia - region threading
 
                 ++this.receivedMovePacketCount;
                 int i = this.receivedMovePacketCount - this.knownMovePacketCount;
@@ -587,7 +614,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 }
 
                 entity.absMoveTo(d3, d4, d5, f, f1);
-                this.player.absMoveTo(d3, d4, d5, this.player.getYRot(), this.player.getXRot()); // CraftBukkit
+                //this.player.absMoveTo(d3, d4, d5, this.player.getYRot(), this.player.getXRot()); // CraftBukkit // Folia - move to repositionAllPassengers
 
                 // Paper start - optimise out extra getCubes
                 boolean teleportBack = flag2; // violating this is always a fail
@@ -600,11 +627,19 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 }
                 if (teleportBack) { // Paper end - optimise out extra getCubes
                     entity.absMoveTo(d0, d1, d2, f, f1);
-                    this.player.absMoveTo(d0, d1, d2, this.player.getYRot(), this.player.getXRot()); // CraftBukkit
+                    //this.player.absMoveTo(d0, d1, d2, this.player.getYRot(), this.player.getXRot()); // CraftBukkit // Folia - not needed, the player is no longer updated
                     this.send(new ClientboundMoveVehiclePacket(entity));
                     return;
                 }
 
+                // Folia start - move to positionRider
+                // this correction is required on folia since we move the connection tick to the beginning of the server
+                // tick, which would make any desync here visible
+                // this will correctly update the passenger positions for all mounted entities
+                // this prevents desync and ensures that all passengers have the correct rider-adjusted position
+                entity.repositionAllPassengers(false);
+                // Folia end - move to positionRider
+
                 // CraftBukkit start - fire PlayerMoveEvent
                 Player player = this.getCraftPlayer();
                 if (!this.hasMoved) {
@@ -644,7 +679,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
                     // If the event is cancelled we move the player back to their old location.
                     if (event.isCancelled()) {
-                        this.teleport(from);
+                        this.player.getBukkitEntity().teleportAsync(from, PlayerTeleportEvent.TeleportCause.PLUGIN); // Folia - region threading
                         return;
                     }
 
@@ -652,7 +687,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                     // there to avoid any 'Moved wrongly' or 'Moved too quickly' errors.
                     // We only do this if the Event was not cancelled.
                     if (!oldTo.equals(event.getTo()) && !event.isCancelled()) {
-                        this.player.getBukkitEntity().teleport(event.getTo(), PlayerTeleportEvent.TeleportCause.PLUGIN);
+                        this.player.getBukkitEntity().teleportAsync(event.getTo(), PlayerTeleportEvent.TeleportCause.PLUGIN); // Folia - region threading
                         return;
                     }
 
@@ -768,7 +803,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         // PacketUtils.ensureRunningOnSameThread(packet, this, this.player.serverLevel()); // Paper - AsyncTabCompleteEvent; run this async
         // CraftBukkit start
         if (this.chatSpamTickCount.addAndGet(io.papermc.paper.configuration.GlobalConfiguration.get().spamLimiter.tabSpamIncrement) > io.papermc.paper.configuration.GlobalConfiguration.get().spamLimiter.tabSpamLimit && !this.server.getPlayerList().isOp(this.player.getGameProfile())) { // Paper - configurable tab spam limits
-            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Paper - Kick event cause
+            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Paper - Kick event cause // Folia - region threading
             return;
         }
         // CraftBukkit end
@@ -780,7 +815,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         // Paper start
         final int index;
         if (packet.getCommand().length() > 64 && ((index = packet.getCommand().indexOf(' ')) == -1 || index >= 64)) {
-            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM);
+            this.disconnect(Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Folia - region threading
             return;
         }
         // Paper end
@@ -805,7 +840,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             }
 
             // This needs to be on main
-            this.server.scheduleOnMain(() -> this.sendServerSuggestions(packet, stringreader));
+            this.player.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> this.sendServerSuggestions(packet, stringreader), null, 1L); // Folia - region threading
         } else if (!completions.isEmpty()) {
             final com.mojang.brigadier.suggestion.SuggestionsBuilder builder0 = new com.mojang.brigadier.suggestion.SuggestionsBuilder(packet.getCommand(), stringreader.getTotalLength());
             final com.mojang.brigadier.suggestion.SuggestionsBuilder builder = builder0.createOffset(builder0.getInput().lastIndexOf(' ') + 1);
@@ -1146,7 +1181,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 int byteLength = testString.getBytes(java.nio.charset.StandardCharsets.UTF_8).length;
                 if (byteLength > 256 * 4) {
                     ServerGamePacketListenerImpl.LOGGER.warn(this.player.getScoreboardName() + " tried to send a book with with a page too large!");
-                    server.scheduleOnMain(() -> this.disconnect("Book too large!", org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_ACTION)); // Paper - kick event cause
+                    this.disconnect("Book too large!", org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_ACTION); // Paper - kick event cause // Folia - region threading
                     return;
                 }
                 byteTotal += byteLength;
@@ -1169,17 +1204,17 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
             if (byteTotal > byteAllowed) {
                 ServerGamePacketListenerImpl.LOGGER.warn(this.player.getScoreboardName() + " tried to send too large of a book. Book Size: " + byteTotal + " - Allowed:  "+ byteAllowed + " - Pages: " + pageList.size());
-                server.scheduleOnMain(() -> this.disconnect("Book too large!", org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_ACTION)); // Paper - kick event cause
+                this.disconnect("Book too large!", org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_ACTION); // Paper - kick event cause // Folia - region threading
                 return;
             }
         }
         // Paper end - Book size limits
         // CraftBukkit start
-        if (this.lastBookTick + 20 > MinecraftServer.currentTick) {
-            server.scheduleOnMain(() -> this.disconnect("Book edited too quickly!", org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_ACTION)); // Paper - kick event cause // Paper - Also ensure this is called on main
+        if (this.lastBookTick + 20 > this.lastTick) {
+            this.disconnect("Book edited too quickly!", org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_ACTION); // Paper - kick event cause // Paper - Also ensure this is called on main // Folia - region threading
             return;
         }
-        this.lastBookTick = MinecraftServer.currentTick;
+        this.lastBookTick = this.lastTick;
         // CraftBukkit end
         int i = packet.getSlot();
 
@@ -1199,7 +1234,19 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 this.updateBookContents(list1, i);
             };
 
-            this.filterTextPacket((List) list).thenAcceptAsync(consumer, this.server);
+            this.filterTextPacket(list).thenAcceptAsync(consumer, // Folia start - region threading
+                (Runnable run) -> {
+                    this.player.getBukkitEntity().taskScheduler.schedule(
+                        (player) -> {
+                            run.run();
+                        },
+                        null, 1L);
+            }).whenComplete((Object res, Throwable thr) -> {
+                if (thr != null) {
+                    LOGGER.error("Failed to handle book update packet", thr);
+                }
+            });
+            // Folia end - region threading
         }
     }
 
@@ -1385,9 +1432,10 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                                 int i = this.receivedMovePacketCount - this.knownMovePacketCount;
 
                                 // CraftBukkit start - handle custom speeds and skipped ticks
-                                this.allowedPlayerTicks += (System.currentTimeMillis() / 50) - this.lastTick;
+                                int currTick = (int)(Util.getMillis() / 50); // Folia - region threading
+                                this.allowedPlayerTicks += currTick - this.lastTick; // Folia - region threading
                                 this.allowedPlayerTicks = Math.max(this.allowedPlayerTicks, 1);
-                                this.lastTick = (int) (System.currentTimeMillis() / 50);
+                                this.lastTick = (int) currTick; // Folia - region threading
 
                                 if (i > Math.max(this.allowedPlayerTicks, 5)) {
                                     ServerGamePacketListenerImpl.LOGGER.debug("{} is sending move packets too frequently ({} packets since last tick)", this.player.getName().getString(), i);
@@ -1577,7 +1625,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
                                     // If the event is cancelled we move the player back to their old location.
                                     if (event.isCancelled()) {
-                                        this.teleport(from);
+                                        this.player.getBukkitEntity().teleportAsync(from, PlayerTeleportEvent.TeleportCause.PLUGIN); // Folia - region threading
                                         return;
                                     }
 
@@ -1585,7 +1633,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                                     // there to avoid any 'Moved wrongly' or 'Moved too quickly' errors.
                                     // We only do this if the Event was not cancelled.
                                     if (!oldTo.equals(event.getTo()) && !event.isCancelled()) {
-                                        this.player.getBukkitEntity().teleport(event.getTo(), PlayerTeleportEvent.TeleportCause.PLUGIN);
+                                        this.player.getBukkitEntity().teleportAsync(event.getTo(), PlayerTeleportEvent.TeleportCause.PLUGIN); // Folia - region threading
                                         return;
                                     }
 
@@ -1805,9 +1853,9 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 if (!this.player.isSpectator()) {
                     // limit how quickly items can be dropped
                     // If the ticks aren't the same then the count starts from 0 and we update the lastDropTick.
-                    if (this.lastDropTick != MinecraftServer.currentTick) {
+                    if (this.lastDropTick != io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick()) {
                         this.dropCount = 0;
-                        this.lastDropTick = MinecraftServer.currentTick;
+                        this.lastDropTick = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick();
                     } else {
                         // Else we increment the drop count and check the amount.
                         this.dropCount++;
@@ -1835,7 +1883,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             case ABORT_DESTROY_BLOCK:
             case STOP_DESTROY_BLOCK:
                 // Paper start - Don't allow digging into unloaded chunks
-                if (this.player.level().getChunkIfLoadedImmediately(blockposition.getX() >> 4, blockposition.getZ() >> 4) == null) {
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(this.player.serverLevel(), blockposition.getX() >> 4, blockposition.getZ() >> 4, 8) || this.player.level().getChunkIfLoadedImmediately(blockposition.getX() >> 4, blockposition.getZ() >> 4) == null) {  // Folia - region threading - don't destroy blocks not owned
                     this.player.connection.ackBlockChangesUpTo(packet.getSequence());
                     return;
                 }
@@ -1919,7 +1967,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             BlockPos blockposition = movingobjectpositionblock.getBlockPos();
             Vec3 vec3d1 = Vec3.atCenterOf(blockposition);
 
-            if (this.player.getEyePosition().distanceToSqr(vec3d1) <= ServerGamePacketListenerImpl.MAX_INTERACTION_DISTANCE) {
+            if (io.papermc.paper.util.TickThread.isTickThreadFor(this.player.serverLevel(), blockposition.getX() >> 4, blockposition.getZ() >> 4, 8) && this.player.getEyePosition().distanceToSqr(vec3d1) <= ServerGamePacketListenerImpl.MAX_INTERACTION_DISTANCE) { // Folia - do not allow players to interact with blocks outside the current region
                 Vec3 vec3d2 = vec3d.subtract(vec3d1);
                 double d0 = 1.0000001D;
 
@@ -2033,7 +2081,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                 Entity entity = packet.getEntity(worldserver);
 
                 if (entity != null) {
-                    this.player.teleportTo(worldserver, entity.getX(), entity.getY(), entity.getZ(), entity.getYRot(), entity.getXRot(), org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.SPECTATE); // CraftBukkit
+                    io.papermc.paper.threadedregions.TeleportUtils.teleport(this.player, false, entity, null, null, Entity.TELEPORT_FLAG_LOAD_CHUNK, org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.SPECTATE, null); // Folia - region threading
                     return;
                 }
             }
@@ -2070,7 +2118,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         }
         // CraftBukkit end
         ServerGamePacketListenerImpl.LOGGER.info("{} lost connection: {}", this.player.getName().getString(), reason.getString());
-        this.removePlayerFromWorld(quitMessage); // Paper - Fix kick event leave message not being sent
+        if (!this.waitingForSwitchToConfig) this.removePlayerFromWorld(quitMessage); // Paper - Fix kick event leave message not being sent // Folia - region threading
         super.onDisconnect(reason, quitMessage); // Paper - Fix kick event leave message not being sent
     }
 
@@ -2079,6 +2127,8 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         this.removePlayerFromWorld(null);
     }
 
+    public boolean hackSwitchingConfig; // Folia - rewrite login process
+
     private void removePlayerFromWorld(@Nullable net.kyori.adventure.text.Component quitMessage) {
         // Paper end - Fix kick event leave message not being sent
         this.chatMessageChain.close();
@@ -2091,6 +2141,8 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         this.player.disconnect();
         // Paper start - Adventure
         quitMessage = quitMessage == null ? this.server.getPlayerList().remove(this.player) : this.server.getPlayerList().remove(this.player, quitMessage); // Paper - pass in quitMessage to fix kick message not being used
+        if (!this.hackSwitchingConfig) this.disconnectPos = this.player.chunkPosition(); // Folia - region threading - note: only set after removing, since it can tick the player
+        if (!this.hackSwitchingConfig) this.player.serverLevel().chunkSource.addTicketAtLevel(DISCONNECT_TICKET, this.disconnectPos, io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL, this.disconnectTicketId); // Folia - region threading - force chunk to be loaded so that the region is not lost
         if ((quitMessage != null) && !quitMessage.equals(net.kyori.adventure.text.Component.empty())) {
             this.server.getPlayerList().broadcastSystemMessage(PaperAdventure.asVanilla(quitMessage), false);
             // Paper end
@@ -2143,7 +2195,9 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         }
         // CraftBukkit end
         if (ServerGamePacketListenerImpl.isChatMessageIllegal(packet.message())) {
+            // Folia - region threading
             this.disconnect(Component.translatable("multiplayer.disconnect.illegal_characters"), org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_CHARACTERS); // Paper - add cause
+            // Folia - region threading
         } else {
             Optional<LastSeenMessages> optional = this.tryHandleChat(packet.lastSeenMessages());
 
@@ -2175,21 +2229,22 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
     @Override
     public void handleChatCommand(ServerboundChatCommandPacket packet) {
         if (ServerGamePacketListenerImpl.isChatMessageIllegal(packet.command())) {
+            // Folia - region threading
             this.disconnect(Component.translatable("multiplayer.disconnect.illegal_characters"), org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_CHARACTERS); // Paper
+            // Folia - region threading
         } else {
             Optional<LastSeenMessages> optional = this.tryHandleChat(packet.lastSeenMessages());
 
             if (optional.isPresent()) {
-                this.server.submit(() -> {
+                this.player.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
                     // CraftBukkit start - SPIGOT-7346: Prevent disconnected players from executing commands
                     if (this.player.hasDisconnected()) {
                         return;
                     }
                     // CraftBukkit end
-
                     this.performChatCommand(packet, (LastSeenMessages) optional.get());
                     this.detectRateSpam("/" + packet.command()); // Spigot
-                });
+                }, null, 1L); // Folia - region threading
             }
 
         }
@@ -2323,7 +2378,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
             String originalFormat = event.getFormat(), originalMessage = event.getMessage();
             this.cserver.getPluginManager().callEvent(event);
 
-            if (PlayerChatEvent.getHandlerList().getRegisteredListeners().length != 0) {
+            if (false && PlayerChatEvent.getHandlerList().getRegisteredListeners().length != 0) { // Folia - region threading
                 // Evil plugins still listening to deprecated event
                 final PlayerChatEvent queueEvent = new PlayerChatEvent(player, event.getMessage(), event.getFormat(), event.getRecipients());
                 queueEvent.setCancelled(event.isCancelled());
@@ -2434,6 +2489,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         if (s.isEmpty()) {
             ServerGamePacketListenerImpl.LOGGER.warn(this.player.getScoreboardName() + " tried to send an empty message");
         } else if (this.getCraftPlayer().isConversing()) {
+            if (true) throw new UnsupportedOperationException(); // Folia - region threading
             final String conversationInput = s;
             this.server.processQueue.add(new Runnable() {
                 @Override
@@ -2674,8 +2730,25 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
     // Spigot End
 
     public void switchToConfig() {
-        this.waitingForSwitchToConfig = true;
+        // Folia start - rewrite login process
+        io.papermc.paper.util.TickThread.ensureTickThread(this.player, "Cannot switch config off-main");
+        if (io.papermc.paper.threadedregions.RegionizedServer.isGlobalTickThread()) {
+            throw new IllegalStateException("Cannot switch config while on global tick thread");
+        }
+        // Folia end - rewrite login process
+        // Folia start - rewrite login process - fix bad ordering of this field write - move after removed from world
+        // the field write ordering is bad as it allows the client to send the response packet before the player is
+        // removed from the world
+        // Folia end - rewrite login process - fix bad ordering of this field write - move after removed from world
+        try { // Folia - rewrite login process - move connection ownership to global region
+            this.hackSwitchingConfig = true; // Folia - rewrite login process - avoid adding logout ticket here and retiring scheduler
         this.removePlayerFromWorld();
+        } finally { // Folia start - rewrite login process - move connection ownership to global region
+            io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.player.serverLevel().getCurrentWorldData();
+            worldData.connections.remove(this.connection);
+            // once waitingForSwitchToConfig is set, the global tick thread will own the connection
+        } // Folia end - rewrite login process - move connection ownership to global region
+        this.waitingForSwitchToConfig = true; // Folia - rewrite login process - fix bad ordering of this field write - moved down
         this.send(new ClientboundStartConfigurationPacket());
     }
 
@@ -2700,7 +2773,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
         this.player.resetLastActionTime();
         this.player.setShiftKeyDown(packet.isUsingSecondaryAction());
-        if (entity != null) {
+        if (io.papermc.paper.util.TickThread.isTickThreadFor(entity) && entity != null) { // Folia - region threading - do not allow interaction of entities outside the current region
             if (!worldserver.getWorldBorder().isWithinBounds(entity.blockPosition())) {
                 return;
             }
@@ -2830,6 +2903,12 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         switch (packetplayinclientcommand_enumclientcommand) {
             case PERFORM_RESPAWN:
                 if (this.player.wonGame) {
+                    // Folia start - region threading
+                    if (true) {
+                        this.player.exitEndCredits();
+                        return;
+                    }
+                    // Folia end - region threading
                     this.player.wonGame = false;
                     this.player = this.server.getPlayerList().respawn(this.player, this.server.getLevel(this.player.getRespawnDimension()), true, null, true, RespawnReason.END_PORTAL, org.bukkit.event.player.PlayerRespawnEvent.RespawnFlag.END_PORTAL); // Paper - Expand PlayerRespawnEvent
                     CriteriaTriggers.CHANGED_DIMENSION.trigger(this.player, Level.END, Level.OVERWORLD);
@@ -2838,6 +2917,18 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
                         return;
                     }
 
+                    // Folia start - region threading
+                    if (true) {
+                        this.player.respawn((ServerPlayer player) -> {
+                            if (ServerGamePacketListenerImpl.this.server.isHardcore()) {
+                                player.setGameMode(GameType.SPECTATOR, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.HARDCORE_DEATH, null); // Paper
+                                ((GameRules.BooleanValue) player.level().getGameRules().getRule(GameRules.RULE_SPECTATORSGENERATECHUNKS)).set(false, player.serverLevel()); // Paper
+                            }
+                        });
+                        return;
+                    }
+                    // Folia end - region threading
+
                     this.player = this.server.getPlayerList().respawn(this.player, false, RespawnReason.DEATH);
                     if (this.server.isHardcore()) {
                         this.player.setGameMode(GameType.SPECTATOR, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.HARDCORE_DEATH, null); // Paper - Expand PlayerGameModeChangeEvent
@@ -3209,7 +3300,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
         // Paper start - auto recipe limit
         if (!org.bukkit.Bukkit.isPrimaryThread()) {
             if (this.recipeSpamPackets.addAndGet(io.papermc.paper.configuration.GlobalConfiguration.get().spamLimiter.recipeSpamIncrement) > io.papermc.paper.configuration.GlobalConfiguration.get().spamLimiter.recipeSpamLimit) {
-                this.server.scheduleOnMain(() -> this.disconnect(net.minecraft.network.chat.Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM)); // Paper - kick event cause
+                this.disconnect(net.minecraft.network.chat.Component.translatable("disconnect.spam"), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Paper - kick event cause // Folia - region threading
                 return;
             }
         }
@@ -3378,7 +3469,18 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
 
         this.filterTextPacket(list).thenAcceptAsync((list1) -> {
             this.updateSignText(packet, list1);
-        }, this.server);
+        }, (Runnable run) -> { // Folia start - region threading
+            this.player.getBukkitEntity().taskScheduler.schedule(
+                (player) -> {
+                    run.run();
+                },
+                null, 1L);
+        }).whenComplete((Object res, Throwable thr) -> {
+            if (thr != null) {
+                LOGGER.error("Failed to handle sign update packet", thr);
+            }
+        });
+        // Folia end - region threading
     }
 
     private void updateSignText(ServerboundSignUpdatePacket packet, List<FilteredText> signText) {
diff --git a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
index c5fa9f4d28f9a7f64a50a902ee5e631bfc00119c..58cdb65083134680230d7070f9f6209f2d32873b 100644
--- a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
@@ -83,7 +83,11 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
         }
         // Paper end - Do not allow logins while the server is shutting down
         if (this.state == ServerLoginPacketListenerImpl.State.VERIFYING) {
-            if (this.connection.isConnected()) { // Paper - prevent logins to be processed even though disconnect was called
+            // Folia start - region threading - rewrite login process
+            String name = this.authenticatedProfile.getName();
+            java.util.UUID uniqueId = this.authenticatedProfile.getId();
+            if (this.server.getPlayerList().pushPendingJoin(name, uniqueId, this.connection)) {
+            // Folia end - region threading - rewrite login process
             this.verifyLoginAndFinishConnectionSetup((GameProfile) Objects.requireNonNull(this.authenticatedProfile));
             } // Paper - prevent logins to be processed even though disconnect was called
         }
@@ -205,7 +209,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
                 }));
             }
 
-            boolean flag = playerlist.disconnectAllPlayersWithProfile(profile, this.player); // CraftBukkit - add player reference
+            boolean flag = false && playerlist.disconnectAllPlayersWithProfile(profile, this.player); // CraftBukkit - add player reference // Folia - rewrite login process - always false here
 
             if (flag) {
                 this.state = ServerLoginPacketListenerImpl.State.WAITING_FOR_DUPE_DISCONNECT;
@@ -325,7 +329,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
         uniqueId = gameprofile.getId();
         // Paper end - Add more fields to AsyncPlayerPreLoginEvent
 
-        if (PlayerPreLoginEvent.getHandlerList().getRegisteredListeners().length != 0) {
+        if (false && PlayerPreLoginEvent.getHandlerList().getRegisteredListeners().length != 0) { // Folia - region threading
             final PlayerPreLoginEvent event = new PlayerPreLoginEvent(playerName, address, uniqueId);
             if (asyncEvent.getResult() != PlayerPreLoginEvent.Result.ALLOWED) {
                 event.disallow(asyncEvent.getResult(), asyncEvent.kickMessage()); // Paper - Adventure
diff --git a/src/main/java/net/minecraft/server/players/BanListEntry.java b/src/main/java/net/minecraft/server/players/BanListEntry.java
index 8b1da1fb5ca27432a39aff6dbc452b793268dab5..e83f3676d5a194fa8d3d1567edcb4b6f7847a4c1 100644
--- a/src/main/java/net/minecraft/server/players/BanListEntry.java
+++ b/src/main/java/net/minecraft/server/players/BanListEntry.java
@@ -10,7 +10,7 @@ import net.minecraft.network.chat.Component;
 
 public abstract class BanListEntry<T> extends StoredUserEntry<T> {
 
-    public static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z", Locale.ROOT);
+    public static final ThreadLocal<SimpleDateFormat> DATE_FORMAT = ThreadLocal.withInitial(() -> new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z", Locale.ROOT)); // Folia - region threading - SDF is not thread-safe
     public static final String EXPIRES_NEVER = "forever";
     protected final Date created;
     protected final String source;
@@ -32,7 +32,7 @@ public abstract class BanListEntry<T> extends StoredUserEntry<T> {
         Date date;
 
         try {
-            date = json.has("created") ? BanListEntry.DATE_FORMAT.parse(json.get("created").getAsString()) : new Date();
+            date = json.has("created") ? BanListEntry.DATE_FORMAT.get().parse(json.get("created").getAsString()) : new Date(); // Folia - region threading - SDF is not thread-safe
         } catch (ParseException parseexception) {
             date = new Date();
         }
@@ -43,7 +43,7 @@ public abstract class BanListEntry<T> extends StoredUserEntry<T> {
         Date date1;
 
         try {
-            date1 = json.has("expires") ? BanListEntry.DATE_FORMAT.parse(json.get("expires").getAsString()) : null;
+            date1 = json.has("expires") ? BanListEntry.DATE_FORMAT.get().parse(json.get("expires").getAsString()) : null; // Folia - region threading - SDF is not thread-safe
         } catch (ParseException parseexception1) {
             date1 = null;
         }
@@ -78,9 +78,9 @@ public abstract class BanListEntry<T> extends StoredUserEntry<T> {
 
     @Override
     protected void serialize(JsonObject json) {
-        json.addProperty("created", BanListEntry.DATE_FORMAT.format(this.created));
+        json.addProperty("created", BanListEntry.DATE_FORMAT.get().format(this.created)); // Folia - region threading - SDF is not thread-safe
         json.addProperty("source", this.source);
-        json.addProperty("expires", this.expires == null ? "forever" : BanListEntry.DATE_FORMAT.format(this.expires));
+        json.addProperty("expires", this.expires == null ? "forever" : BanListEntry.DATE_FORMAT.get().format(this.expires)); // Folia - region threading - SDF is not thread-safe
         json.addProperty("reason", this.reason);
     }
 
@@ -89,7 +89,7 @@ public abstract class BanListEntry<T> extends StoredUserEntry<T> {
         Date expires = null;
 
         try {
-            expires = jsonobject.has("expires") ? BanListEntry.DATE_FORMAT.parse(jsonobject.get("expires").getAsString()) : null;
+            expires = jsonobject.has("expires") ? BanListEntry.DATE_FORMAT.get().parse(jsonobject.get("expires").getAsString()) : null; // Folia - region threading - SDF is not thread-safe
         } catch (ParseException ex) {
             // Guess we don't have a date
         }
diff --git a/src/main/java/net/minecraft/server/players/OldUsersConverter.java b/src/main/java/net/minecraft/server/players/OldUsersConverter.java
index 45d4638d568ea2aee805aa1b0542533019e5870d..599feff33b43623d7c6bd22158afa730efd5370d 100644
--- a/src/main/java/net/minecraft/server/players/OldUsersConverter.java
+++ b/src/main/java/net/minecraft/server/players/OldUsersConverter.java
@@ -510,7 +510,7 @@ public class OldUsersConverter {
         Date date1;
 
         try {
-            date1 = BanListEntry.DATE_FORMAT.parse(dateString);
+            date1 = BanListEntry.DATE_FORMAT.get().parse(dateString); // Folia - region threading - SDF is not thread-safe
         } catch (ParseException parseexception) {
             date1 = fallback;
         }
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 1e5f709115007ff19901c0a6c3cf884d9e4d3a6c..08daa5ed0b4b599836b97eef1e53e630e7659443 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -132,10 +132,10 @@ public abstract class PlayerList {
     public static final Component DUPLICATE_LOGIN_DISCONNECT_MESSAGE = Component.translatable("multiplayer.disconnect.duplicate_login");
     private static final Logger LOGGER = LogUtils.getLogger();
     private static final int SEND_PLAYER_INFO_INTERVAL = 600;
-    private static final SimpleDateFormat BAN_DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss z");
+    private static final ThreadLocal<SimpleDateFormat> BAN_DATE_FORMAT = ThreadLocal.withInitial(() -> new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss z")); // Folia - region threading - SDF is not thread-safe
     private final MinecraftServer server;
     public final List<ServerPlayer> players = new java.util.concurrent.CopyOnWriteArrayList(); // CraftBukkit - ArrayList -> CopyOnWriteArrayList: Iterator safety
-    private final Map<UUID, ServerPlayer> playersByUUID = Maps.newHashMap();
+    private final Map<UUID, ServerPlayer> playersByUUID = new java.util.concurrent.ConcurrentHashMap<>(); // Folia - region threading - change to CHM - Note: we do NOT expect concurrency PER KEY!
     private final UserBanList bans;
     private final IpBanList ipBans;
     private final ServerOpList ops;
@@ -156,9 +156,63 @@ public abstract class PlayerList {
 
     // CraftBukkit start
     private CraftServer cserver;
-    private final Map<String,ServerPlayer> playersByName = new java.util.HashMap<>();
+    private final Map<String,ServerPlayer> playersByName = new java.util.concurrent.ConcurrentHashMap<>(); // Folia - region threading - change to CHM - Note: we do NOT expect concurrency PER KEY!
     public @Nullable String collideRuleTeamName; // Paper - Configurable player collision
 
+    // Folia start - region threading
+    private final Object connectionsStateLock = new Object();
+    private final Map<String, Connection> connectionByName = new java.util.HashMap<>();
+    private final Map<UUID, Connection> connectionById = new java.util.HashMap<>();
+    private final it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<Connection> usersCountedAgainstLimit = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>();
+
+    public boolean pushPendingJoin(String userName, UUID byId, Connection conn) {
+        userName = userName.toLowerCase(java.util.Locale.ROOT);
+        Connection conflictingName, conflictingId;
+        synchronized (this.connectionsStateLock) {
+            conflictingName = this.connectionByName.get(userName);
+            conflictingId = this.connectionById.get(byId);
+
+            if (conflictingName == null && conflictingId == null) {
+                this.connectionByName.put(userName, conn);
+                this.connectionById.put(byId, conn);
+            }
+        }
+
+        Component message = Component.translatable("multiplayer.disconnect.duplicate_login", new Object[0]);
+
+        if (conflictingId != null || conflictingName != null) {
+            if (conflictingName != null && conflictingName.isPlayerConnected()) {
+                conflictingName.disconnectSafely(message, org.bukkit.event.player.PlayerKickEvent.Cause.DUPLICATE_LOGIN);
+            }
+            if (conflictingName != conflictingId && conflictingId != null && conflictingId.isPlayerConnected()) {
+                conflictingId.disconnectSafely(message, org.bukkit.event.player.PlayerKickEvent.Cause.DUPLICATE_LOGIN);
+            }
+        }
+
+        return conflictingName == null && conflictingId == null;
+    }
+
+    public void removeConnection(String userName, UUID byId, Connection conn) {
+        userName = userName.toLowerCase(java.util.Locale.ROOT);
+        synchronized (this.connectionsStateLock) {
+            this.connectionByName.remove(userName, conn);
+            this.connectionById.remove(byId, conn);
+            this.usersCountedAgainstLimit.remove(conn);
+        }
+    }
+
+    private boolean countConnection(Connection conn, int limit) {
+        synchronized (this.connectionsStateLock) {
+            int count = this.usersCountedAgainstLimit.size();
+            if (count >= limit) {
+                return false;
+            }
+            this.usersCountedAgainstLimit.add(conn);
+            return true;
+        }
+    }
+    // Folia end - region threading
+
     public PlayerList(MinecraftServer server, LayeredRegistryAccess<RegistryLayer> registryManager, PlayerDataStorage saveHandler, int maxPlayers) {
         this.cserver = server.server = new CraftServer((DedicatedServer) server, this);
         server.console = new com.destroystokyo.paper.console.TerminalConsoleCommandSender(); // Paper
@@ -179,7 +233,7 @@ public abstract class PlayerList {
     }
     abstract public void loadAndSaveFiles(); // Paper - fix converting txt to json file; moved from DedicatedPlayerList constructor
 
-    public void placeNewPlayer(Connection connection, ServerPlayer player, CommonListenerCookie clientData) {
+    public void loadSpawnForNewPlayer(final Connection connection, final ServerPlayer player, final CommonListenerCookie clientData, org.apache.commons.lang3.mutable.MutableObject<CompoundTag> data, org.apache.commons.lang3.mutable.MutableObject<String> lastKnownName, ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) { // Folia - region threading - rewrite login process
         player.isRealPlayer = true; // Paper
         player.loginTime = System.currentTimeMillis(); // Paper - Replace OfflinePlayer#getLastPlayed
         GameProfile gameprofile = player.getGameProfile();
@@ -258,18 +312,42 @@ public abstract class PlayerList {
             player.spawnReason = org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT; // set Player SpawnReason to DEFAULT on first login
             // Paper start - reset to main world spawn if first spawn or invalid world
         }
+        // Folia start - region threading - rewrite login process
+        // must write to these before toComplete is invoked
+        data.setValue(nbttagcompound);
+        lastKnownName.setValue(s);
+        // Folia end - region threading - rewrite login process
         if (nbttagcompound == null || invalidPlayerWorld) {
             // Paper end - reset to main world spawn if first spawn or invalid world
-            player.fudgeSpawnLocation(worldserver1); // Paper - Don't move existing players to world spawn
+            ServerPlayer.fudgeSpawnLocation(worldserver1, player, toComplete); // Paper - Don't move existing players to world spawn // Folia - region threading
+        } else { // Folia start - region threading - rewrite login process
+            worldserver1.loadChunksForMoveAsync(
+                player.getBoundingBox(),
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                (c) -> {
+                    toComplete.complete(io.papermc.paper.util.MCUtil.toLocation(worldserver1, player.position()));
+                }
+            );
         }
+        // Folia end - region threading - rewrite login process
         // Paper end - Entity#getEntitySpawnReason
+        // Folia start - region threading - rewrite login process
+        return;
+    }
+    // nbttagcomound -> player data
+    // s -> last known name
+    public void placeNewPlayer(Connection connection, ServerPlayer player, CommonListenerCookie clientData, CompoundTag nbttagcompound, String s, Location selectedSpawn) {
+        ServerLevel worldserver1 = ((CraftWorld)selectedSpawn.getWorld()).getHandle();
+        player.setPosRaw(selectedSpawn.getX(), selectedSpawn.getY(), selectedSpawn.getZ());
+        player.lastSave = System.nanoTime(); // changed to nanoTime
+        // Folia end - region threading - rewrite login process
         player.setServerLevel(worldserver1);
         String s1 = connection.getLoggableAddress(this.server.logIPs());
 
         // Spigot start - spawn location event
         Player spawnPlayer = player.getBukkitEntity();
         org.spigotmc.event.player.PlayerSpawnLocationEvent ev = new com.destroystokyo.paper.event.player.PlayerInitialSpawnEvent(spawnPlayer, spawnPlayer.getLocation()); // Paper use our duplicate event
-        this.cserver.getPluginManager().callEvent(ev);
+        //this.cserver.getPluginManager().callEvent(ev); // Folia - region threading - TODO WTF TO DO WITH THIS EVENT?
 
         Location loc = ev.getSpawnLocation();
         worldserver1 = ((CraftWorld) loc.getWorld()).getHandle();
@@ -288,6 +366,10 @@ public abstract class PlayerList {
 
         player.loadGameTypes(nbttagcompound);
         ServerGamePacketListenerImpl playerconnection = new ServerGamePacketListenerImpl(this.server, connection, player, clientData);
+        // Folia start - rewrite login process
+        // only after setting the connection listener to game type, add the connection to this regions list
+        worldserver1.getCurrentWorldData().connections.add(connection);
+        // Folia end - rewrite login process
         GameRules gamerules = worldserver1.getGameRules();
         boolean flag = gamerules.getBoolean(GameRules.RULE_DO_IMMEDIATE_RESPAWN);
         boolean flag1 = gamerules.getBoolean(GameRules.RULE_REDUCEDDEBUGINFO);
@@ -303,7 +385,7 @@ public abstract class PlayerList {
         this.sendPlayerPermissionLevel(player);
         player.getStats().markAllDirty();
         player.getRecipeBook().sendInitialRecipeBook(player);
-        this.updateEntireScoreboard(worldserver1.getScoreboard(), player);
+        if (false) this.updateEntireScoreboard(worldserver1.getScoreboard(), player); // Folia - region threading
         this.server.invalidateStatus();
         MutableComponent ichatmutablecomponent;
 
@@ -345,7 +427,7 @@ public abstract class PlayerList {
         this.cserver.getPluginManager().callEvent(playerJoinEvent);
 
         if (!player.connection.isAcceptingMessages()) {
-            return;
+            //return; // Folia - region threading - must still allow the player to connect, as we must add to chunk map before handling disconnect
         }
 
         final net.kyori.adventure.text.Component jm = playerJoinEvent.joinMessage();
@@ -360,8 +442,7 @@ public abstract class PlayerList {
         ClientboundPlayerInfoUpdatePacket packet = ClientboundPlayerInfoUpdatePacket.createPlayerInitializing(List.of(player)); // Paper - Add Listing API for Player
 
         final List<ServerPlayer> onlinePlayers = Lists.newArrayListWithExpectedSize(this.players.size() - 1); // Paper - Use single player info update packet on join
-        for (int i = 0; i < this.players.size(); ++i) {
-            ServerPlayer entityplayer1 = (ServerPlayer) this.players.get(i);
+        for (ServerPlayer entityplayer1 : this.players) { // Folia - region threading
 
             if (entityplayer1.getBukkitEntity().canSee(bukkitPlayer)) {
                 // Paper start - Add Listing API for Player
@@ -483,7 +564,7 @@ public abstract class PlayerList {
         // Paper start - Configurable player collision; Add to collideRule team if needed
         final net.minecraft.world.scores.Scoreboard scoreboard = this.getServer().getLevel(Level.OVERWORLD).getScoreboard();
         final PlayerTeam collideRuleTeam = scoreboard.getPlayerTeam(this.collideRuleTeamName);
-        if (this.collideRuleTeamName != null && collideRuleTeam != null && player.getTeam() == null) {
+        if (false && this.collideRuleTeamName != null && collideRuleTeam != null && player.getTeam() == null) { // Folia - region threading
             scoreboard.addPlayerToTeam(player.getScoreboardName(), collideRuleTeam);
         }
         // Paper end - Configurable player collision
@@ -577,7 +658,7 @@ public abstract class PlayerList {
 
     protected void save(ServerPlayer player) {
         if (!player.getBukkitEntity().isPersistent()) return; // CraftBukkit
-        player.lastSave = MinecraftServer.currentTick; // Paper - Incremental chunk and player saving
+        player.lastSave = System.nanoTime(); // Folia - region threading - changed to nanoTime tracking
         this.playerIo.save(player);
         ServerStatsCounter serverstatisticmanager = (ServerStatsCounter) player.getStats(); // CraftBukkit
 
@@ -617,7 +698,7 @@ public abstract class PlayerList {
         // CraftBukkit end
 
         // Paper start - Configurable player collision; Remove from collideRule team if needed
-        if (this.collideRuleTeamName != null) {
+        if (false && this.collideRuleTeamName != null) { // Folia - region threading
             final net.minecraft.world.scores.Scoreboard scoreBoard = this.server.getLevel(Level.OVERWORLD).getScoreboard();
             final PlayerTeam team = scoreBoard.getPlayersTeam(this.collideRuleTeamName);
             if (entityplayer.getTeam() == team && team != null) {
@@ -657,7 +738,7 @@ public abstract class PlayerList {
 
         entityplayer.unRide();
         worldserver.removePlayerImmediately(entityplayer, Entity.RemovalReason.UNLOADED_WITH_PLAYER);
-        entityplayer.retireScheduler(); // Paper - Folia schedulers
+        // Folia - region threading - move to onDisconnect of common packet listener
         entityplayer.getAdvancements().stopListening();
         this.players.remove(entityplayer);
         this.playersByName.remove(entityplayer.getScoreboardName().toLowerCase(java.util.Locale.ROOT)); // Spigot
@@ -676,8 +757,7 @@ public abstract class PlayerList {
         // CraftBukkit start
         // this.broadcastAll(new ClientboundPlayerInfoRemovePacket(List.of(entityplayer.getUUID())));
         ClientboundPlayerInfoRemovePacket packet = new ClientboundPlayerInfoRemovePacket(List.of(entityplayer.getUUID()));
-        for (int i = 0; i < this.players.size(); i++) {
-            ServerPlayer entityplayer2 = (ServerPlayer) this.players.get(i);
+        for (ServerPlayer entityplayer2 : this.players) { // Folia - region threading
 
             if (entityplayer2.getBukkitEntity().canSee(entityplayer.getBukkitEntity())) {
                 entityplayer2.connection.send(packet);
@@ -702,19 +782,12 @@ public abstract class PlayerList {
 
         ServerPlayer entityplayer;
 
-        for (int i = 0; i < this.players.size(); ++i) {
-            entityplayer = (ServerPlayer) this.players.get(i);
-            if (entityplayer.getUUID().equals(uuid) || (io.papermc.paper.configuration.GlobalConfiguration.get().proxies.isProxyOnlineMode() && entityplayer.getGameProfile().getName().equalsIgnoreCase(gameprofile.getName()))) { // Paper - validate usernames
-                list.add(entityplayer);
-            }
-        }
+        // Folia - region threading - rewrite login process - moved to pushPendingJoin
 
         Iterator iterator = list.iterator();
 
         while (iterator.hasNext()) {
-            entityplayer = (ServerPlayer) iterator.next();
-            this.save(entityplayer); // CraftBukkit - Force the player's inventory to be saved
-            entityplayer.connection.disconnect(Component.translatable("multiplayer.disconnect.duplicate_login"), org.bukkit.event.player.PlayerKickEvent.Cause.DUPLICATE_LOGIN); // Paper - kick event cause
+            // Folia - moved to pushPendingJoin
         }
 
         // Instead of kicking then returning, we need to store the kick reason
@@ -733,7 +806,7 @@ public abstract class PlayerList {
 
             ichatmutablecomponent = Component.translatable("multiplayer.disconnect.banned.reason", gameprofilebanentry.getReason());
             if (gameprofilebanentry.getExpires() != null) {
-                ichatmutablecomponent.append((Component) Component.translatable("multiplayer.disconnect.banned.expiration", PlayerList.BAN_DATE_FORMAT.format(gameprofilebanentry.getExpires())));
+                ichatmutablecomponent.append((Component) Component.translatable("multiplayer.disconnect.banned.expiration", PlayerList.BAN_DATE_FORMAT.get().format(gameprofilebanentry.getExpires()))); // Folia - region threading - SDF is not thread-safe
             }
 
             // return chatmessage;
@@ -746,14 +819,14 @@ public abstract class PlayerList {
 
             ichatmutablecomponent = Component.translatable("multiplayer.disconnect.banned_ip.reason", ipbanentry.getReason());
             if (ipbanentry.getExpires() != null) {
-                ichatmutablecomponent.append((Component) Component.translatable("multiplayer.disconnect.banned_ip.expiration", PlayerList.BAN_DATE_FORMAT.format(ipbanentry.getExpires())));
+                ichatmutablecomponent.append((Component) Component.translatable("multiplayer.disconnect.banned_ip.expiration", PlayerList.BAN_DATE_FORMAT.get().format(ipbanentry.getExpires()))); // Folia - region threading - SDF is not thread-safe
             }
 
             // return chatmessage;
             event.disallow(PlayerLoginEvent.Result.KICK_BANNED, io.papermc.paper.adventure.PaperAdventure.asAdventure(ichatmutablecomponent)); // Paper - Adventure
         } else {
             // return this.players.size() >= this.maxPlayers && !this.canBypassPlayerLimit(gameprofile) ? IChatBaseComponent.translatable("multiplayer.disconnect.server_full") : null;
-            if (this.players.size() >= this.maxPlayers && !this.canBypassPlayerLimit(gameprofile)) {
+            if (!this.countConnection(loginlistener.connection, this.maxPlayers) && !this.canBypassPlayerLimit(gameprofile)) { // Folia - region threading - we control connection state here now async, not player list size
                 event.disallow(PlayerLoginEvent.Result.KICK_FULL, net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer.legacySection().deserialize(org.spigotmc.SpigotConfig.serverFullMessage)); // Spigot // Paper - Adventure
             }
         }
@@ -819,6 +892,11 @@ public abstract class PlayerList {
 
     public ServerPlayer respawn(ServerPlayer entityplayer, ServerLevel worldserver, boolean flag, Location location, boolean avoidSuffocation, RespawnReason reason, org.bukkit.event.player.PlayerRespawnEvent.RespawnFlag...respawnFlags) {
         // Paper end - Expand PlayerRespawnEvent
+        // Folia start - region threading
+        if (true) {
+            throw new UnsupportedOperationException("Must use teleportAsync while in region threading");
+        }
+        // Folia end - region threading
         entityplayer.stopRiding(); // CraftBukkit
         this.players.remove(entityplayer);
         this.playersByName.remove(entityplayer.getScoreboardName().toLowerCase(java.util.Locale.ROOT)); // Spigot
@@ -1018,10 +1096,10 @@ public abstract class PlayerList {
     public void tick() {
         if (++this.sendAllPlayerInfoIn > 600) {
             // CraftBukkit start
-            for (int i = 0; i < this.players.size(); ++i) {
-                final ServerPlayer target = (ServerPlayer) this.players.get(i);
+            ServerPlayer[] players = this.players.toArray(new ServerPlayer[0]); // Folia - region threading
+            for (final ServerPlayer target : players) { // Folia - region threading
 
-                target.connection.send(new ClientboundPlayerInfoUpdatePacket(EnumSet.of(ClientboundPlayerInfoUpdatePacket.Action.UPDATE_LATENCY), this.players.stream().filter(new Predicate<ServerPlayer>() {
+                target.connection.send(new ClientboundPlayerInfoUpdatePacket(EnumSet.of(ClientboundPlayerInfoUpdatePacket.Action.UPDATE_LATENCY), java.util.Arrays.stream(players).filter(new Predicate<ServerPlayer>() { // Folia - region threading
                     @Override
                     public boolean test(ServerPlayer input) {
                         return target.getBukkitEntity().canSee(input.getBukkitEntity());
@@ -1047,18 +1125,17 @@ public abstract class PlayerList {
 
     // CraftBukkit start - add a world/entity limited version
     public void broadcastAll(Packet packet, net.minecraft.world.entity.player.Player entityhuman) {
-        for (int i = 0; i < this.players.size(); ++i) {
-            ServerPlayer entityplayer =  this.players.get(i);
+        for (ServerPlayer entityplayer : this.players) { // Folia - region threading
             if (entityhuman != null && !entityplayer.getBukkitEntity().canSee(entityhuman.getBukkitEntity())) {
                 continue;
             }
-            ((ServerPlayer) this.players.get(i)).connection.send(packet);
+            entityplayer.connection.send(packet); // Folia - region threading
         }
     }
 
     public void broadcastAll(Packet packet, Level world) {
-        for (int i = 0; i < world.players().size(); ++i) {
-            ((ServerPlayer) world.players().get(i)).connection.send(packet);
+        for (net.minecraft.world.entity.player.Player player : world.players()) { // Folia - region threading
+            ((ServerPlayer) player).connection.send(packet); // Folia - region threading
         }
 
     }
@@ -1102,8 +1179,7 @@ public abstract class PlayerList {
         if (scoreboardteam == null) {
             this.broadcastSystemMessage(message, false);
         } else {
-            for (int i = 0; i < this.players.size(); ++i) {
-                ServerPlayer entityplayer = (ServerPlayer) this.players.get(i);
+            for (ServerPlayer entityplayer : this.players) { // Folia - region threading
 
                 if (entityplayer.getTeam() != scoreboardteam) {
                     entityplayer.sendSystemMessage(message);
@@ -1114,10 +1190,12 @@ public abstract class PlayerList {
     }
 
     public String[] getPlayerNamesArray() {
-        String[] astring = new String[this.players.size()];
+        List<ServerPlayer> players = new java.util.ArrayList<>(this.players); // Folia start - region threading
+        String[] astring = new String[players.size()];
 
-        for (int i = 0; i < this.players.size(); ++i) {
-            astring[i] = ((ServerPlayer) this.players.get(i)).getGameProfile().getName();
+        for (int i = 0; i < players.size(); ++i) {
+            astring[i] = ((ServerPlayer) players.get(i)).getGameProfile().getName();
+            // Folia end - region threading
         }
 
         return astring;
@@ -1136,7 +1214,9 @@ public abstract class PlayerList {
         ServerPlayer entityplayer = this.getPlayer(profile.getId());
 
         if (entityplayer != null) {
+            entityplayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
             this.sendPlayerPermissionLevel(entityplayer);
+            }, null, 1L); // Folia - region threading
         }
 
     }
@@ -1146,7 +1226,10 @@ public abstract class PlayerList {
         ServerPlayer entityplayer = this.getPlayer(profile.getId());
 
         if (entityplayer != null) {
+            entityplayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
             this.sendPlayerPermissionLevel(entityplayer);
+            }, null, 1L); // Folia - region threading
+
         }
 
     }
@@ -1207,8 +1290,7 @@ public abstract class PlayerList {
     }
 
     public void broadcast(@Nullable net.minecraft.world.entity.player.Player player, double x, double y, double z, double distance, ResourceKey<Level> worldKey, Packet<?> packet) {
-        for (int i = 0; i < this.players.size(); ++i) {
-            ServerPlayer entityplayer = (ServerPlayer) this.players.get(i);
+        for (ServerPlayer entityplayer : this.players) { // Folia - region threading
 
             // CraftBukkit start - Test if player receiving packet can see the source of the packet
             if (player != null && !entityplayer.getBukkitEntity().canSee(player.getBukkitEntity())) {
@@ -1238,12 +1320,21 @@ public abstract class PlayerList {
         io.papermc.paper.util.MCUtil.ensureMain("Save Players" , () -> { // Paper - Ensure main
         MinecraftTimings.savePlayers.startTiming(); // Paper
         int numSaved = 0;
-        long now = MinecraftServer.currentTick;
-        for (int i = 0; i < this.players.size(); ++i) {
-            ServerPlayer entityplayer = this.players.get(i);
-            if (interval == -1 || now - entityplayer.lastSave >= interval) {
+        long now = System.nanoTime(); // Folia - region threading
+        int max = io.papermc.paper.configuration.GlobalConfiguration.get().playerAutoSave.maxPerTick(); // Folia - region threading
+        long timeInterval = (long)interval * io.papermc.paper.threadedregions.TickRegionScheduler.TIME_BETWEEN_TICKS; // Folia - region threading
+        for (ServerPlayer entityplayer : this.players) { // Folia start - region threading
+            if (!io.papermc.paper.util.TickThread.isTickThreadFor(entityplayer)) {
+                continue;
+            }
+            // Folia end - region threading
+            if (interval == -1 || now - entityplayer.lastSave >= timeInterval) { // Folia - region threading
                 this.save(entityplayer);
-                if (interval != -1 && ++numSaved >= io.papermc.paper.configuration.GlobalConfiguration.get().playerAutoSave.maxPerTick()) { break; }
+                // Folia start - region threading
+                if (interval != -1 && max != -1 && ++numSaved >= max) {
+                    break;
+                }
+                // Folia end - region threading
             }
             // Paper end - Incremental chunk and player saving
         }
@@ -1362,6 +1453,20 @@ public abstract class PlayerList {
     }
 
     public void removeAll(boolean isRestarting) {
+        // Folia start - region threading
+        // just send disconnect packet, don't modify state
+        for (ServerPlayer player : this.players) {
+            final Component shutdownMessage = io.papermc.paper.adventure.PaperAdventure.asVanilla(this.server.server.shutdownMessage()); // Paper - Adventure
+            // CraftBukkit end
+
+            player.connection.send(new net.minecraft.network.protocol.common.ClientboundDisconnectPacket(shutdownMessage), net.minecraft.network.PacketSendListener.thenRun(() -> {
+                player.connection.connection.disconnect(shutdownMessage);
+            }));
+        }
+        if (true) {
+            return;
+        }
+        // Folia end - region threading
         // Paper end
         // CraftBukkit start - disconnect safely
         for (ServerPlayer player : this.players) {
@@ -1371,7 +1476,7 @@ public abstract class PlayerList {
         // CraftBukkit end
 
         // Paper start - Configurable player collision; Remove collideRule team if it exists
-        if (this.collideRuleTeamName != null) {
+        if (false && this.collideRuleTeamName != null) { // Folia - region threading
             final net.minecraft.world.scores.Scoreboard scoreboard = this.getServer().getLevel(Level.OVERWORLD).getScoreboard();
             final PlayerTeam team = scoreboard.getPlayersTeam(this.collideRuleTeamName);
             if (team != null) scoreboard.removePlayerTeam(team);
diff --git a/src/main/java/net/minecraft/server/players/StoredUserList.java b/src/main/java/net/minecraft/server/players/StoredUserList.java
index 7e133752ccb1ea7c0b4fa781feb1a88e2cfdcf6d..9756d1750f40bda0578f4c965953a27c384e7db2 100644
--- a/src/main/java/net/minecraft/server/players/StoredUserList.java
+++ b/src/main/java/net/minecraft/server/players/StoredUserList.java
@@ -103,6 +103,7 @@ public abstract class StoredUserList<K, V extends StoredUserEntry<K>> {
     }
 
     public void save() throws IOException {
+        synchronized (this) { // Folia - region threading
         this.removeExpired(); // Paper - remove expired values before saving
         JsonArray jsonarray = new JsonArray();
         Stream<JsonObject> stream = this.map.values().stream().map((jsonlistentry) -> { // CraftBukkit - decompile error
@@ -133,10 +134,12 @@ public abstract class StoredUserList<K, V extends StoredUserEntry<K>> {
         if (bufferedwriter != null) {
             bufferedwriter.close();
         }
+        } // Folia - region threading
 
     }
 
     public void load() throws IOException {
+        synchronized (this) { // Folia - region threading
         if (this.file.exists()) {
             BufferedReader bufferedreader = Files.newReader(this.file, StandardCharsets.UTF_8);
 
@@ -193,5 +196,6 @@ public abstract class StoredUserList<K, V extends StoredUserEntry<K>> {
             }
 
         }
+        } // Folia - region threading
     }
 }
diff --git a/src/main/java/net/minecraft/util/SortedArraySet.java b/src/main/java/net/minecraft/util/SortedArraySet.java
index 0793dfe47e68a2b48b010aad5b12dcfa1701293a..50e3ad4ce20915943fbd9115cec221a374e778fb 100644
--- a/src/main/java/net/minecraft/util/SortedArraySet.java
+++ b/src/main/java/net/minecraft/util/SortedArraySet.java
@@ -90,7 +90,7 @@ public class SortedArraySet<T> extends AbstractSet<T> {
         return Arrays.binarySearch(this.contents, 0, this.size, object, this.comparator);
     }
 
-    private static int getInsertionPosition(int binarySearchResult) {
+    public static int getInsertionPosition(int binarySearchResult) { // Folia - region threading - public
         return -binarySearchResult - 1;
     }
 
@@ -177,6 +177,40 @@ public class SortedArraySet<T> extends AbstractSet<T> {
         }
     }
     // Paper end - rewrite chunk system
+    // Folia start - region threading
+    public int binarySearch(final T search) {
+        return this.findIndex(search);
+    }
+
+    public int insertAndGetIdx(final T value) {
+        final int idx = this.findIndex(value);
+        if (idx >= 0) {
+            // exists already
+            return idx;
+        }
+
+        this.addInternal(value, getInsertionPosition(idx));
+        return idx;
+    }
+
+    public T removeFirst() {
+        final T ret = this.contents[0];
+
+        this.removeInternal(0);
+
+        return ret;
+    }
+
+    public T removeLast() {
+        final int index = --this.size;
+
+        final T ret = this.contents[index];
+
+        this.contents[index] = null;
+
+        return ret;
+    }
+    // Folia end - region threading
 
     @Override
     public boolean remove(Object object) {
diff --git a/src/main/java/net/minecraft/util/SpawnUtil.java b/src/main/java/net/minecraft/util/SpawnUtil.java
index c5d54abfcbd74c3041d9a46f77705460fa65ce30..025bf2306851347a12035d81e4dd92a47dc00dba 100644
--- a/src/main/java/net/minecraft/util/SpawnUtil.java
+++ b/src/main/java/net/minecraft/util/SpawnUtil.java
@@ -59,7 +59,7 @@ public class SpawnUtil {
                         return Optional.of(t0);
                     }
 
-                    t0.discard(null); // CraftBukkit - add Bukkit remove cause
+                    //t0.discard(null); // CraftBukkit - add Bukkit remove cause // Folia - region threading
                 }
             }
         }
diff --git a/src/main/java/net/minecraft/world/RandomSequences.java b/src/main/java/net/minecraft/world/RandomSequences.java
index a9bbe79831183e119562e27038e4a9c651529bf4..645c0823718a4013aba149c693b267ea59691d2d 100644
--- a/src/main/java/net/minecraft/world/RandomSequences.java
+++ b/src/main/java/net/minecraft/world/RandomSequences.java
@@ -20,7 +20,7 @@ public class RandomSequences extends SavedData {
     private int salt;
     private boolean includeWorldSeed = true;
     private boolean includeSequenceId = true;
-    private final Map<ResourceLocation, RandomSequence> sequences = new Object2ObjectOpenHashMap<>();
+    private final Map<ResourceLocation, RandomSequence> sequences = new java.util.concurrent.ConcurrentHashMap<>(); // Folia - region threading
 
     public static SavedData.Factory<RandomSequences> factory(long seed) {
         return new SavedData.Factory<>(() -> new RandomSequences(seed), nbt -> load(seed, nbt), DataFixTypes.SAVED_DATA_RANDOM_SEQUENCES);
@@ -113,61 +113,61 @@ public class RandomSequences extends SavedData {
         @Override
         public RandomSource fork() {
             RandomSequences.this.setDirty();
-            return this.random.fork();
+            synchronized (this.random) { return this.random.fork(); } // Folia - region threading
         }
 
         @Override
         public PositionalRandomFactory forkPositional() {
             RandomSequences.this.setDirty();
-            return this.random.forkPositional();
+            synchronized (this.random) { return this.random.forkPositional(); } // Folia - region threading
         }
 
         @Override
         public void setSeed(long seed) {
             RandomSequences.this.setDirty();
-            this.random.setSeed(seed);
+            synchronized (this.random) { this.random.setSeed(seed); } // Folia - region threading
         }
 
         @Override
         public int nextInt() {
             RandomSequences.this.setDirty();
-            return this.random.nextInt();
+            synchronized (this.random) { return this.random.nextInt(); } // Folia - region threading
         }
 
         @Override
         public int nextInt(int bound) {
             RandomSequences.this.setDirty();
-            return this.random.nextInt(bound);
+            synchronized (this.random) { return this.random.nextInt(bound); } // Folia - region threading
         }
 
         @Override
         public long nextLong() {
             RandomSequences.this.setDirty();
-            return this.random.nextLong();
+            synchronized (this.random) { return this.random.nextLong(); } // Folia - region threading
         }
 
         @Override
         public boolean nextBoolean() {
             RandomSequences.this.setDirty();
-            return this.random.nextBoolean();
+            synchronized (this.random) { return this.random.nextBoolean(); } // Folia - region threading
         }
 
         @Override
         public float nextFloat() {
             RandomSequences.this.setDirty();
-            return this.random.nextFloat();
+            synchronized (this.random) { return this.random.nextFloat(); } // Folia - region threading
         }
 
         @Override
         public double nextDouble() {
             RandomSequences.this.setDirty();
-            return this.random.nextDouble();
+            synchronized (this.random) { return this.random.nextDouble(); } // Folia - region threading
         }
 
         @Override
         public double nextGaussian() {
             RandomSequences.this.setDirty();
-            return this.random.nextGaussian();
+            synchronized (this.random) { return this.random.nextGaussian(); } // Folia - region threading
         }
 
         @Override
diff --git a/src/main/java/net/minecraft/world/damagesource/CombatTracker.java b/src/main/java/net/minecraft/world/damagesource/CombatTracker.java
index 7056c8ca7a87748f14142c6af274aae492f29f1c..c92063c527aef85c932453d4761fd1955542dd98 100644
--- a/src/main/java/net/minecraft/world/damagesource/CombatTracker.java
+++ b/src/main/java/net/minecraft/world/damagesource/CombatTracker.java
@@ -52,7 +52,7 @@ public class CombatTracker {
     }
 
     private Component getMessageForAssistedFall(Entity attacker, Component attackerDisplayName, String itemDeathTranslationKey, String deathTranslationKey) {
-        ItemStack itemStack = attacker instanceof LivingEntity livingEntity ? livingEntity.getMainHandItem() : ItemStack.EMPTY;
+        ItemStack itemStack = attacker instanceof LivingEntity livingEntity && io.papermc.paper.util.TickThread.isTickThreadFor(livingEntity) ? livingEntity.getMainHandItem() : ItemStack.EMPTY; // Folia - region threading
         return !itemStack.isEmpty() && itemStack.hasCustomHoverName()
             ? Component.translatable(itemDeathTranslationKey, this.mob.getDisplayName(), attackerDisplayName, itemStack.getDisplayName())
             : Component.translatable(deathTranslationKey, this.mob.getDisplayName(), attackerDisplayName);
@@ -79,7 +79,7 @@ public class CombatTracker {
 
     @Nullable
     private static Component getDisplayName(@Nullable Entity entity) {
-        return entity == null ? null : entity.getDisplayName();
+        return entity == null || !io.papermc.paper.util.TickThread.isTickThreadFor(entity) ? null : entity.getDisplayName(); // Folia - region threading
     }
 
     public Component getDeathMessage() {
diff --git a/src/main/java/net/minecraft/world/damagesource/DamageSource.java b/src/main/java/net/minecraft/world/damagesource/DamageSource.java
index b26e4d58ea1898a5e4b31c3d6ab33f38835ab2c6..90781fffbb7e6293d3a30d6041dc30186c84caaf 100644
--- a/src/main/java/net/minecraft/world/damagesource/DamageSource.java
+++ b/src/main/java/net/minecraft/world/damagesource/DamageSource.java
@@ -156,13 +156,13 @@ public class DamageSource {
             LivingEntity entityliving1 = killed.getKillCredit();
             String s1 = s + ".player";
 
-            return entityliving1 != null ? Component.translatable(s1, killed.getDisplayName(), entityliving1.getDisplayName()) : Component.translatable(s, killed.getDisplayName());
+            return entityliving1 != null && io.papermc.paper.util.TickThread.isTickThreadFor(entityliving1) ? Component.translatable(s1, killed.getDisplayName(), entityliving1.getDisplayName()) : Component.translatable(s, killed.getDisplayName()); // Folia - region threading
         } else {
             Component ichatbasecomponent = this.causingEntity == null ? this.directEntity.getDisplayName() : this.causingEntity.getDisplayName();
             Entity entity = this.causingEntity;
             ItemStack itemstack;
 
-            if (entity instanceof LivingEntity) {
+            if (entity instanceof LivingEntity livingEntity && io.papermc.paper.util.TickThread.isTickThreadFor(livingEntity)) { // Folia - region threading
                 LivingEntity entityliving2 = (LivingEntity) entity;
 
                 itemstack = entityliving2.getMainHandItem();
diff --git a/src/main/java/net/minecraft/world/damagesource/FallLocation.java b/src/main/java/net/minecraft/world/damagesource/FallLocation.java
index e9df8f8541b8a1b85c7d2925ff3cba813007a1ef..35e3e67c0c74f95007c55ee8fb44822a712a25b1 100644
--- a/src/main/java/net/minecraft/world/damagesource/FallLocation.java
+++ b/src/main/java/net/minecraft/world/damagesource/FallLocation.java
@@ -35,7 +35,7 @@ public record FallLocation(String id) {
     @Nullable
     public static FallLocation getCurrentFallLocation(LivingEntity entity) {
         Optional<BlockPos> optional = entity.getLastClimbablePos();
-        if (optional.isPresent()) {
+        if (optional.isPresent() && io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)entity.level(), optional.get())) { // Folia - region threading
             BlockState blockState = entity.level().getBlockState(optional.get());
             return blockToFallLocation(blockState);
         } else {
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 637478fd8a284e6833cf8f5fa17ccf9d73d1dd3f..fe07f0881f5835974f00c65498a31a19c8ead97c 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -170,7 +170,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     // Paper start - Share random for entities to make them more random
     public static RandomSource SHARED_RANDOM = new RandomRandomSource();
-    private static final class RandomRandomSource extends java.util.Random implements net.minecraft.world.level.levelgen.BitRandomSource {
+    public static final class RandomRandomSource extends java.util.Random implements net.minecraft.world.level.levelgen.BitRandomSource { // Folia - region threading
         private boolean locked = false;
 
         @Override
@@ -244,7 +244,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     public com.destroystokyo.paper.loottable.PaperLootableInventoryData lootableData; // Paper
     public boolean collisionLoadChunks = false; // Paper
-    private CraftEntity bukkitEntity;
+    private volatile CraftEntity bukkitEntity; // Folia - region threading
 
     public @org.jetbrains.annotations.Nullable net.minecraft.server.level.ChunkMap.TrackedEntity tracker; // Paper
     public CraftEntity getBukkitEntity() {
@@ -378,7 +378,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
     private boolean hasGlowingTag;
     private final Set<String> tags;
     private final double[] pistonDeltas;
-    private long pistonDeltasGameTime;
+    private long pistonDeltasGameTime = Long.MIN_VALUE; // Folia - region threading
     private EntityDimensions dimensions;
     private float eyeHeight;
     public boolean isInPowderSnow;
@@ -479,28 +479,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         this.isLegacyTrackingEntity = isLegacyTrackingEntity;
     }
 
-    public final com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> getPlayersInTrackRange() {
-        // determine highest range of passengers
-        if (this.passengers.isEmpty()) {
-            return ((ServerLevel)this.level).getChunkSource().chunkMap.playerEntityTrackerTrackMaps[this.trackingRangeType.ordinal()]
-                .getObjectsInRange(MCUtil.getCoordinateKey(this));
-        }
-        Iterable<Entity> passengers = this.getIndirectPassengers();
-        net.minecraft.server.level.ChunkMap chunkMap = ((ServerLevel)this.level).getChunkSource().chunkMap;
-        org.spigotmc.TrackingRange.TrackingRangeType type = this.trackingRangeType;
-        int range = chunkMap.getEntityTrackerRange(type.ordinal());
-
-        for (Entity passenger : passengers) {
-            org.spigotmc.TrackingRange.TrackingRangeType passengerType = passenger.trackingRangeType;
-            int passengerRange = chunkMap.getEntityTrackerRange(passengerType.ordinal());
-            if (passengerRange > range) {
-                type = passengerType;
-                range = passengerRange;
-            }
-        }
-
-        return chunkMap.playerEntityTrackerTrackMaps[type.ordinal()].getObjectsInRange(MCUtil.getCoordinateKey(this));
-    }
+    // Folia - region ticking
     // Paper end - optimise entity tracking
     public float getBukkitYaw() {
         return this.yRot;
@@ -567,6 +546,19 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     public boolean updatingSectionStatus = false;
     // Paper end
+    // Folia start - region ticking
+    public void updateTicks(long fromTickOffset, long fromRedstoneTimeOffset) {
+        if (this.activatedTick != Integer.MIN_VALUE) {
+            this.activatedTick += fromTickOffset;
+        }
+        if (this.activatedImmunityTick != Integer.MIN_VALUE) {
+            this.activatedImmunityTick += fromTickOffset;
+        }
+        if (this.pistonDeltasGameTime != Long.MIN_VALUE) {
+            this.pistonDeltasGameTime += fromRedstoneTimeOffset;
+        }
+    }
+    // Folia end - region ticking
 
     public Entity(EntityType<?> type, Level world) {
         this.id = Entity.ENTITY_COUNTER.incrementAndGet();
@@ -825,6 +817,12 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     // CraftBukkit start
     public void postTick() {
+        // Folia start - region threading
+        // moved to doPortalLogic
+        if (true) {
+            return;
+        }
+        // Folia end - region threading
         // No clean way to break out of ticking once the entity has been copied to a new world, so instead we move the portalling later in the tick cycle
         if (!(this instanceof ServerPlayer) && this.isAlive()) { // Paper - don't attempt to teleport dead entities
             this.handleNetherPortal();
@@ -847,7 +845,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         this.walkDistO = this.walkDist;
         this.xRotO = this.getXRot();
         this.yRotO = this.getYRot();
-        if (this instanceof ServerPlayer) this.handleNetherPortal(); // CraftBukkit - // Moved up to postTick
+        //if (this instanceof ServerPlayer) this.handleNetherPortal(); // CraftBukkit - // Moved up to postTick // Folia - region threading - ONLY allow in postTick()
         if (this.canSpawnSprintParticle()) {
             this.spawnSprintParticle();
         }
@@ -1105,8 +1103,8 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         } else {
             this.wasOnFire = this.isOnFire();
             if (movementType == MoverType.PISTON) {
-                this.activatedTick = Math.max(this.activatedTick, MinecraftServer.currentTick + 20); // Paper
-                this.activatedImmunityTick = Math.max(this.activatedImmunityTick, MinecraftServer.currentTick + 20);   // Paper
+                this.activatedTick = Math.max(this.activatedTick, io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + 20); // Paper
+                this.activatedImmunityTick = Math.max(this.activatedImmunityTick, io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + 20);   // Paper
                 movement = this.limitPistonMovement(movement);
                 if (movement.equals(Vec3.ZERO)) {
                     return;
@@ -1433,7 +1431,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         if (movement.lengthSqr() <= 1.0E-7D) {
             return movement;
         } else {
-            long i = this.level().getGameTime();
+            long i = this.level().getRedstoneGameTime(); // Folia - region threading
 
             if (i != this.pistonDeltasGameTime) {
                 Arrays.fill(this.pistonDeltas, 0.0D);
@@ -3018,7 +3016,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
                 this.passengers = ImmutableList.copyOf(list);
             }
 
-            this.gameEvent(GameEvent.ENTITY_MOUNT, passenger);
+            if (!passenger.hasNullCallback()) this.gameEvent(GameEvent.ENTITY_MOUNT, passenger); // Folia - region threading - do not fire game events for entities not added
         }
     }
 
@@ -3066,7 +3064,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
             }
 
             entity.boardingCooldown = 60;
-            this.gameEvent(GameEvent.ENTITY_DISMOUNT, entity);
+            if (!entity.hasNullCallback()) this.gameEvent(GameEvent.ENTITY_DISMOUNT, entity); // Folia - region threading - do not fire game events for entities not added
         }
         return true; // CraftBukkit
     }
@@ -3346,6 +3344,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     @Nullable
     public PlayerTeam getTeam() {
+        // Folia start - region threading
+        if (true) {
+            return null;
+        }
+        // Folia end - region threading
         if (!this.level().paperConfig().scoreboards.allowNonPlayerEntitiesOnScoreboards && !(this instanceof Player)) { return null; } // Paper - Perf: Disable Scoreboards for non players by default
         return this.level().getScoreboard().getPlayersTeam(this.getScoreboardName());
     }
@@ -3635,6 +3638,775 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         this.portalEntrancePos = original.portalEntrancePos;
     }
 
+    // Folia start - region threading
+    public static class EntityTreeNode {
+        @Nullable
+        public EntityTreeNode parent;
+        public Entity root;
+        @Nullable
+        public EntityTreeNode[] passengers;
+
+        public EntityTreeNode(EntityTreeNode parent, Entity root) {
+            this.parent = parent;
+            this.root = root;
+        }
+
+        public EntityTreeNode(EntityTreeNode parent, Entity root, EntityTreeNode[] passengers) {
+            this.parent = parent;
+            this.root = root;
+            this.passengers = passengers;
+        }
+
+        public List<EntityTreeNode> getFullTree() {
+            List<EntityTreeNode> ret = new java.util.ArrayList<>();
+            ret.add(this);
+
+            // this is just a BFS except we don't remove from head, we just advance down the list
+            for (int i = 0; i < ret.size(); ++i) {
+                EntityTreeNode node = ret.get(i);
+
+                EntityTreeNode[] passengers = node.passengers;
+                if (passengers == null) {
+                    continue;
+                }
+                for (EntityTreeNode passenger : passengers) {
+                    ret.add(passenger);
+                }
+            }
+
+            return ret;
+        }
+
+        public void restore() {
+            java.util.ArrayDeque<EntityTreeNode> queue = new java.util.ArrayDeque<>();
+            queue.add(this);
+
+            EntityTreeNode curr;
+            while ((curr = queue.pollFirst()) != null) {
+                EntityTreeNode[] passengers = curr.passengers;
+                if (passengers == null) {
+                    continue;
+                }
+
+                List<Entity> newPassengers = new java.util.ArrayList<>();
+                for (EntityTreeNode passenger : passengers) {
+                    newPassengers.add(passenger.root);
+                    passenger.root.vehicle = curr.root;
+                }
+
+                curr.root.passengers = ImmutableList.copyOf(newPassengers);
+            }
+        }
+
+        public void addTracker() {
+            for (final EntityTreeNode node : this.getFullTree()) {
+                if (node.root.tracker != null) {
+                    for (final ServerPlayer player : node.root.level.getLocalPlayers()) {
+                        node.root.tracker.updatePlayer(player);
+                    }
+                }
+            }
+        }
+
+        public void clearTracker() {
+            for (final EntityTreeNode node : this.getFullTree()) {
+                if (node.root.tracker != null) {
+                    node.root.tracker.removeNonTickThreadPlayers();
+                    for (final ServerPlayer player : node.root.level.getLocalPlayers()) {
+                        node.root.tracker.removePlayer(player);
+                    }
+                }
+            }
+        }
+
+        public void adjustRiders(boolean teleport) {
+            java.util.ArrayDeque<EntityTreeNode> queue = new java.util.ArrayDeque<>();
+            queue.add(this);
+
+            EntityTreeNode curr;
+            while ((curr = queue.pollFirst()) != null) {
+                EntityTreeNode[] passengers = curr.passengers;
+                if (passengers == null) {
+                    continue;
+                }
+
+                for (EntityTreeNode passenger : passengers) {
+                    curr.root.positionRider(passenger.root, teleport ? Entity::moveTo : Entity::setPos);
+                }
+            }
+        }
+    }
+
+    public void repositionAllPassengers(boolean teleport) {
+        this.makePassengerTree().adjustRiders(teleport);
+    }
+
+    protected EntityTreeNode makePassengerTree() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot read passengers off of the main thread");
+
+        EntityTreeNode root = new EntityTreeNode(null, this);
+        java.util.ArrayDeque<EntityTreeNode> queue = new java.util.ArrayDeque<>();
+        queue.add(root);
+        EntityTreeNode curr;
+        while ((curr = queue.pollFirst()) != null) {
+            Entity vehicle = curr.root;
+            List<Entity> passengers = vehicle.passengers;
+            if (passengers.isEmpty()) {
+                continue;
+            }
+
+            EntityTreeNode[] treePassengers = new EntityTreeNode[passengers.size()];
+            curr.passengers = treePassengers;
+
+            for (int i = 0; i < passengers.size(); ++i) {
+                Entity passenger = passengers.get(i);
+                queue.addLast(treePassengers[i] = new EntityTreeNode(curr, passenger));
+            }
+        }
+
+        return root;
+    }
+
+    protected EntityTreeNode detachPassengers() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot adjust passengers/vehicle off of the main thread");
+
+        EntityTreeNode root = new EntityTreeNode(null, this);
+        java.util.ArrayDeque<EntityTreeNode> queue = new java.util.ArrayDeque<>();
+        queue.add(root);
+        EntityTreeNode curr;
+        while ((curr = queue.pollFirst()) != null) {
+            Entity vehicle = curr.root;
+            List<Entity> passengers = vehicle.passengers;
+            if (passengers.isEmpty()) {
+                continue;
+            }
+
+            vehicle.passengers = ImmutableList.of();
+
+            EntityTreeNode[] treePassengers = new EntityTreeNode[passengers.size()];
+            curr.passengers = treePassengers;
+
+            for (int i = 0; i < passengers.size(); ++i) {
+                Entity passenger = passengers.get(i);
+                passenger.vehicle = null;
+                queue.addLast(treePassengers[i] = new EntityTreeNode(curr, passenger));
+            }
+        }
+
+        return root;
+    }
+
+    /**
+     * This flag will perform an async load on the chunks determined by
+     * the entity's bounding box before teleporting the entity.
+     */
+    public static final long TELEPORT_FLAG_LOAD_CHUNK = 1L << 0;
+    /**
+     * This flag requires the entity being teleported to be a root vehicle.
+     * Thus, if you want to teleport a non-root vehicle, you must dismount
+     * the target entity before calling teleport, otherwise the
+     * teleport will be refused.
+     */
+    public static final long TELEPORT_FLAG_TELEPORT_PASSENGERS = 1L << 1;
+    /**
+     * The flag will dismount any passengers and dismout from the current vehicle
+     * to teleport if and only if dismounting would result in the teleport being allowed.
+     */
+    public static final long TELEPORT_FLAG_UNMOUNT = 1L << 2;
+
+    protected void placeSingleSync(ServerLevel originWorld, ServerLevel destination, EntityTreeNode treeNode, long teleportFlags) {
+        destination.addDuringTeleport(this);
+    }
+
+    protected final void placeInAsync(ServerLevel originWorld, ServerLevel destination, long teleportFlags,
+                                      EntityTreeNode passengerTree, java.util.function.Consumer<Entity> teleportComplete) {
+        Vec3 pos = this.position();
+        ChunkPos posChunk = new ChunkPos(
+            io.papermc.paper.util.CoordinateUtils.getChunkX(pos),
+            io.papermc.paper.util.CoordinateUtils.getChunkZ(pos)
+        );
+
+        // ensure the region is always ticking in case of a shutdown
+        // otherwise, the shutdown will not be able to complete the shutdown as it requires a ticking region
+        Long teleportHoldId = Long.valueOf(TELEPORT_HOLD_TICKET_GEN.getAndIncrement());
+        originWorld.chunkSource.addTicketAtLevel(
+            TicketType.TELEPORT_HOLD_TICKET, posChunk,
+            io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+            teleportHoldId
+        );
+        final ServerLevel.PendingTeleport pendingTeleport = new ServerLevel.PendingTeleport(passengerTree, pos);
+        destination.pushPendingTeleport(pendingTeleport);
+
+        Runnable scheduleEntityJoin = () -> {
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                destination,
+                io.papermc.paper.util.CoordinateUtils.getChunkX(pos), io.papermc.paper.util.CoordinateUtils.getChunkZ(pos),
+                () -> {
+                    if (!destination.removePendingTeleport(pendingTeleport)) {
+                        // shutdown logic placed the entity already, and we are shutting down - do nothing to ensure
+                        // we do not produce any errors here
+                        return;
+                    }
+                    originWorld.chunkSource.removeTicketAtLevel(
+                        TicketType.TELEPORT_HOLD_TICKET, posChunk,
+                        io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+                        teleportHoldId
+                    );
+                    List<EntityTreeNode> fullTree = passengerTree.getFullTree();
+                    for (EntityTreeNode node : fullTree) {
+                        node.root.placeSingleSync(originWorld, destination, node, teleportFlags);
+                    }
+
+                    // restore passenger tree
+                    passengerTree.restore();
+                    passengerTree.adjustRiders(true);
+
+                    // invoke post dimension change now
+                    for (EntityTreeNode node : fullTree) {
+                        node.root.postChangeDimension();
+                    }
+
+                    if (teleportComplete != null) {
+                        teleportComplete.accept(Entity.this);
+                    }
+                }
+            );
+        };
+
+        if ((teleportFlags & TELEPORT_FLAG_LOAD_CHUNK) != 0L) {
+            destination.loadChunksForMoveAsync(
+                Entity.this.getBoundingBox(), ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                (chunkList) -> {
+                    for (net.minecraft.world.level.chunk.ChunkAccess chunk : chunkList) {
+                        destination.chunkSource.addTicketAtLevel(
+                            TicketType.POST_TELEPORT, chunk.getPos(),
+                            io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.FULL_LOADED_TICKET_LEVEL,
+                            Integer.valueOf(Entity.this.getId())
+                        );
+                    }
+                    scheduleEntityJoin.run();
+                }
+            );
+        } else {
+            scheduleEntityJoin.run();
+        }
+    }
+
+    protected boolean canTeleportAsync() {
+        return !this.hasNullCallback() && !this.isRemoved() && this.isAlive() && (!(this instanceof net.minecraft.world.entity.LivingEntity livingEntity) || !livingEntity.isSleeping());
+    }
+
+    // Mojang for whatever reason has started storing positions to cache certain physics properties that entities collide with
+    // As usual though, they don't properly do anything to prevent serious desync with respect to the current entity position
+    // We add additional logic to reset these before teleporting to prevent issues with them possibly tripping thread checks.
+    protected void resetStoredPositions() {
+        this.mainSupportingBlockPos = Optional.empty();
+    }
+
+    protected void teleportSyncSameRegion(Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate) {
+        if (yaw != null) {
+            this.setYRot(yaw.floatValue());
+            this.setYHeadRot(yaw.floatValue());
+        }
+        if (pitch != null) {
+            this.setXRot(pitch.floatValue());
+        }
+        if (speedDirectionUpdate != null) {
+            this.setDeltaMovement(speedDirectionUpdate.normalize().scale(this.getDeltaMovement().length()));
+        }
+        this.moveTo(pos.x, pos.y, pos.z);
+        this.resetStoredPositions();
+    }
+
+    protected void transform(Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate) {
+        if (yaw != null) {
+            this.setYRot(yaw.floatValue());
+            this.setYHeadRot(yaw.floatValue());
+        }
+        if (pitch != null) {
+            this.setXRot(pitch.floatValue());
+        }
+        if (speedDirectionUpdate != null) {
+            this.setDeltaMovement(speedDirectionUpdate);
+        }
+        if (pos != null) {
+            this.setPosRaw(pos.x, pos.y, pos.z);
+        }
+    }
+
+    protected Entity transformForAsyncTeleport(ServerLevel destination, Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate) {
+        this.removeAfterChangingDimensions(); // remove before so that any CBEntity#getHandle call affects this entity before copying
+
+        Entity copy = this.getType().create(destination);
+        copy.restoreFrom(this);
+        copy.transform(pos, yaw, pitch, speedDirectionUpdate);
+        // vanilla code used to call remove _after_ copying, and some stuff is required to be after copy - so add hook here
+        // for example, clearing of inventory after switching dimensions
+        this.postRemoveAfterChangingDimensions();
+
+        return copy;
+    }
+
+    public final boolean teleportAsync(ServerLevel destination, Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate,
+                                       org.bukkit.event.player.PlayerTeleportEvent.TeleportCause cause, long teleportFlags,
+                                       java.util.function.Consumer<Entity> teleportComplete) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot teleport entity async");
+
+        if (!ServerLevel.isInSpawnableBounds(new BlockPos(io.papermc.paper.util.CoordinateUtils.getBlockX(pos), io.papermc.paper.util.CoordinateUtils.getBlockY(pos), io.papermc.paper.util.CoordinateUtils.getBlockZ(pos)))) {
+            return false;
+        }
+
+        if (!this.canTeleportAsync()) {
+            return false;
+        }
+        this.getBukkitEntity(); // force bukkit entity to be created before TPing
+        if ((teleportFlags & TELEPORT_FLAG_UNMOUNT) == 0L) {
+            for (Entity entity : this.getIndirectPassengers()) {
+                if (!entity.canTeleportAsync()) {
+                    return false;
+                }
+                entity.getBukkitEntity(); // force bukkit entity to be created before TPing
+            }
+        } else {
+            this.unRide();
+        }
+
+        if ((teleportFlags & TELEPORT_FLAG_TELEPORT_PASSENGERS) != 0L) {
+            if (this.isPassenger()) {
+                return false;
+            }
+        } else {
+            if (this.isVehicle() || this.isPassenger()) {
+                return false;
+            }
+        }
+
+        // TODO any events that can modify go HERE
+
+        // check for same region
+        if (destination == this.level()) {
+            Vec3 currPos = this.position();
+            if (
+                destination.regioniser.getRegionAtUnsynchronised(
+                    io.papermc.paper.util.CoordinateUtils.getChunkX(currPos), io.papermc.paper.util.CoordinateUtils.getChunkZ(currPos)
+                ) == destination.regioniser.getRegionAtUnsynchronised(
+                    io.papermc.paper.util.CoordinateUtils.getChunkX(pos), io.papermc.paper.util.CoordinateUtils.getChunkZ(pos)
+                )
+            ) {
+                EntityTreeNode passengerTree = this.detachPassengers();
+                // Note: The client does not accept position updates for controlled entities. So, we must
+                // perform a lot of tracker updates here to make it all work out.
+
+                // first, clear the tracker
+                passengerTree.clearTracker();
+                for (EntityTreeNode entity : passengerTree.getFullTree()) {
+                    entity.root.teleportSyncSameRegion(pos, yaw, pitch, speedDirectionUpdate);
+                }
+
+                passengerTree.restore();
+                // re-add to the tracker once the tree is restored
+                passengerTree.addTracker();
+
+                // adjust entities to final position
+                passengerTree.adjustRiders(true);
+
+                // the tracker clear/add logic is only used in the same region, as the other logic
+                // performs add/remove from world logic which will also perform add/remove tracker logic
+
+                if (teleportComplete != null) {
+                    teleportComplete.accept(this);
+                }
+                return true;
+            }
+        }
+
+        EntityTreeNode passengerTree = this.detachPassengers();
+        List<EntityTreeNode> fullPassengerTree = passengerTree.getFullTree();
+        ServerLevel originWorld = (ServerLevel)this.level;
+
+        for (EntityTreeNode node : fullPassengerTree) {
+            node.root.preChangeDimension();
+        }
+
+        for (EntityTreeNode node : fullPassengerTree) {
+            node.root = node.root.transformForAsyncTeleport(destination, pos, yaw, pitch, speedDirectionUpdate);
+        }
+
+        passengerTree.root.placeInAsync(originWorld, destination, teleportFlags, passengerTree, teleportComplete);
+
+        return true;
+    }
+
+    public void preChangeDimension() {
+
+    }
+
+    public void postChangeDimension() {
+        this.resetStoredPositions();
+    }
+
+    protected static enum PortalType {
+        NETHER, END;
+    }
+
+    public boolean doPortalLogic() {
+        if (this.tryNetherPortal()) {
+            return true;
+        }
+        if (this.tryEndPortal()) {
+            return true;
+        }
+        return false;
+    }
+
+    protected boolean tryEndPortal() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot portal entity async");
+        BlockPos pos = this.portalBlock;
+        ServerLevel world = this.portalWorld;
+        this.portalBlock = null;
+        this.portalWorld = null;
+
+        if (pos == null || world == null || world != this.level) {
+            return false;
+        }
+
+        if (this.isPassenger() || this.isVehicle() || !this.canChangeDimensions() || this.isRemoved() || !this.valid || !this.isAlive()) {
+            return false;
+        }
+
+        return this.endPortalLogicAsync();
+    }
+
+    protected boolean tryNetherPortal() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot portal entity async");
+
+        int portalWaitTime = this.getPortalWaitTime();
+
+        if (this.isInsidePortal) {
+            // if we are in a nether portal still, this flag will be set next tick.
+            this.isInsidePortal = false;
+            if (this.portalTime++ >= portalWaitTime) {
+                this.portalTime = portalWaitTime;
+                if (this.netherPortalLogicAsync()) {
+                    return true;
+                }
+            }
+        } else {
+            // rapidly decrease portal time
+            this.portalTime = Math.max(0, this.portalTime - 4);
+        }
+
+        this.processPortalCooldown();
+        return false;
+    }
+
+    public boolean endPortalLogicAsync() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot portal entity async");
+
+        ServerLevel destination = this.getServer().getLevel(this.level().getTypeKey() == LevelStem.END ? Level.OVERWORLD : Level.END);
+        if (destination == null) {
+            // wat
+            return false;
+        }
+
+        return this.portalToAsync(destination, false, PortalType.END, null);
+    }
+
+    public boolean netherPortalLogicAsync() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot portal entity async");
+
+        ServerLevel destination = this.getServer().getLevel(this.level().getTypeKey() == LevelStem.NETHER ? Level.OVERWORLD : Level.NETHER);
+        if (destination == null) {
+            // wat
+            return false;
+        }
+
+        return this.portalToAsync(destination, false, PortalType.NETHER, null);
+    }
+
+    private static final java.util.concurrent.atomic.AtomicLong CREATE_PORTAL_DOUBLE_CHECK = new java.util.concurrent.atomic.AtomicLong();
+    private static final java.util.concurrent.atomic.AtomicLong TELEPORT_HOLD_TICKET_GEN = new java.util.concurrent.atomic.AtomicLong();
+
+    // To simplify portal logic, in region threading both players
+    // and non-player entities will create portals. By guaranteeing
+    // that the teleportation can take place, we can simply
+    // remove the entity, find/create the portal, and place async.
+    // If we have to worry about whether the entity may not teleport,
+    // we need to first search, then report back, ...
+    protected void findOrCreatePortalAsync(ServerLevel origin, ServerLevel destination, PortalType type,
+                                           ca.spottedleaf.concurrentutil.completable.Completable<PortalInfo> portalInfoCompletable) {
+        switch (type) {
+            // end portal logic is quite simple, the spawn in the end is fixed and when returning to the overworld
+            // we just select the spawn position
+            case END: {
+                if (destination.getTypeKey() == LevelStem.END) {
+                    BlockPos targetPos = ServerLevel.END_SPAWN_POINT;
+                    // need to load chunks so we can create the platform
+                    destination.loadChunksAsync(
+                        targetPos, 16, // load 16 blocks to be safe from block physics
+                        ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGH,
+                        (chunks) -> {
+                            ServerLevel.makeObsidianPlatform(destination, null, targetPos);
+
+                            // the portal obsidian is placed at targetPos.y - 2, so if we want to place the entity
+                            // on the obsidian, we need to spawn at targetPos.y - 1
+                            portalInfoCompletable.complete(
+                                new PortalInfo(Vec3.atBottomCenterOf(targetPos.below()), Vec3.ZERO, 90.0f, 0.0f, destination, null)
+                            );
+                        }
+                    );
+                } else {
+                    BlockPos spawnPos = destination.getSharedSpawnPos();
+                    // need to load chunk for heightmap
+                    destination.loadChunksAsync(
+                        spawnPos, 0,
+                        ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGH,
+                        (chunks) -> {
+                            BlockPos adjustedSpawn = destination.getHeightmapPos(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, spawnPos);
+
+                            // done
+                            portalInfoCompletable.complete(
+                                new PortalInfo(Vec3.atBottomCenterOf(adjustedSpawn), Vec3.ZERO, 90.0f, 0.0f, destination, null)
+                            );
+                        }
+                    );
+                }
+
+                break;
+            }
+            // for the nether logic, we need to first load the chunks in radius to empty (so that POI is created)
+            // then we can search for an existing portal using the POI routines
+            // if we don't find a portal, then we bring the chunks in the create radius to full and
+            // create it
+            case NETHER: {
+                // hoisted from the create fallback, so that we can avoid the sync load later if we need it
+                BlockState originalPortalBlock = this.portalEntrancePos == null ? null : origin.getBlockStateIfLoaded(this.portalEntrancePos);
+                Direction.Axis originalPortalDirection = originalPortalBlock == null ? Direction.Axis.X :
+                    originalPortalBlock.getOptionalValue(net.minecraft.world.level.block.NetherPortalBlock.AXIS).orElse(Direction.Axis.X);
+                BlockUtil.FoundRectangle originalPortalRectangle =
+                    originalPortalBlock == null || !originalPortalBlock.hasProperty(BlockStateProperties.HORIZONTAL_AXIS)
+                        ? null
+                        : BlockUtil.getLargestRectangleAround(
+                            this.portalEntrancePos, originalPortalDirection, 21, Direction.Axis.Y, 21,
+                            (blockpos) -> {
+                                return origin.getBlockStateFromEmptyChunkIfLoaded(blockpos) == originalPortalBlock;
+                            }
+                        );
+
+                boolean destinationIsNether = destination.getTypeKey() == LevelStem.NETHER;
+
+                int portalSearchRadius = origin.paperConfig().environment.portalSearchVanillaDimensionScaling && destinationIsNether ?
+                    (int)(destination.paperConfig().environment.portalSearchRadius / destination.dimensionType().coordinateScale()) :
+                    destination.paperConfig().environment.portalSearchRadius;
+                int portalCreateRadius = destination.paperConfig().environment.portalCreateRadius;
+
+                WorldBorder destinationBorder = destination.getWorldBorder();
+                double dimensionScale = DimensionType.getTeleportationScale(origin.dimensionType(), destination.dimensionType());
+                BlockPos targetPos = destination.getWorldBorder().clampToBounds(this.getX() * dimensionScale, this.getY(), this.getZ() * dimensionScale);
+
+                ca.spottedleaf.concurrentutil.completable.Completable<BlockUtil.FoundRectangle> portalFound
+                    = new ca.spottedleaf.concurrentutil.completable.Completable<>();
+
+                // post portal find/create logic
+                portalFound.addWaiter(
+                    (BlockUtil.FoundRectangle portal, Throwable thr) -> {
+                        // no portal could be created
+                        if (portal == null) {
+                            portalInfoCompletable.complete(
+                                new PortalInfo(Vec3.atCenterOf(targetPos), Vec3.ZERO, 90.0f, 0.0f, destination, null)
+                            );
+                            return;
+                        }
+
+                        Vec3 relativePos = originalPortalRectangle == null ?
+                            new Vec3(0.5, 0.0, 0.0) :
+                            Entity.this.getRelativePortalPosition(originalPortalDirection, originalPortalRectangle);
+
+                        portalInfoCompletable.complete(
+                            PortalShape.createPortalInfo(
+                                destination, portal, originalPortalDirection, relativePos,
+                                Entity.this, Entity.this.getDeltaMovement(), Entity.this.getYRot(), Entity.this.getXRot(), null
+                            )
+                        );
+                    }
+                );
+
+                // kick off search for existing portal or creation
+                destination.loadChunksAsync(
+                    // add 32 so that the final search for a portal frame doesn't load any chunks
+                    targetPos, portalSearchRadius + 32,
+                    net.minecraft.world.level.chunk.ChunkStatus.EMPTY,
+                    ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGH,
+                    (chunks) -> {
+                        BlockUtil.FoundRectangle portal =
+                            destination.getPortalForcer().findPortalAround(targetPos, destinationBorder, portalSearchRadius).orElse(null);
+                        if (portal != null) {
+                            portalFound.complete(portal);
+                            return;
+                        }
+
+                        // add tickets so that we can re-search for a portal once the chunks are loaded
+                        Long ticketId = Long.valueOf(CREATE_PORTAL_DOUBLE_CHECK.getAndIncrement());
+                        for (net.minecraft.world.level.chunk.ChunkAccess chunk : chunks) {
+                            destination.chunkSource.addTicketAtLevel(
+                                TicketType.NETHER_PORTAL_DOUBLE_CHECK, chunk.getPos(),
+                                io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+                                ticketId
+                            );
+                        }
+
+                        // no portal found - create one
+                        destination.loadChunksAsync(
+                            targetPos, portalCreateRadius + 32,
+                            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGH,
+                            (chunks2) -> {
+                                // don't need the tickets anymore
+                                // note: we expect removeTicketsAtLevel to add an unknown ticket for us automatically
+                                // if the ticket level were to decrease
+                                for (net.minecraft.world.level.chunk.ChunkAccess chunk : chunks) {
+                                    destination.chunkSource.removeTicketAtLevel(
+                                        TicketType.NETHER_PORTAL_DOUBLE_CHECK, chunk.getPos(),
+                                        io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+                                        ticketId
+                                    );
+                                }
+
+                                // when two entities portal at the same time, it is possible that both entities reach this
+                                // part of the code - and create a double portal
+                                // to fix this, we just issue another search to try and see if another entity created
+                                // a portal nearby
+                                BlockUtil.FoundRectangle existingTryAgain =
+                                    destination.getPortalForcer().findPortalAround(targetPos, destinationBorder, portalSearchRadius).orElse(null);
+                                if (existingTryAgain != null) {
+                                    portalFound.complete(existingTryAgain);
+                                    return;
+                                }
+
+                                // we do not have the correct entity reference here
+                                BlockUtil.FoundRectangle createdPortal =
+                                    destination.getPortalForcer().createPortal(targetPos, originalPortalDirection, null, portalCreateRadius).orElse(null);
+                                // if it wasn't created, passing null is expected here
+                                portalFound.complete(createdPortal);
+                            }
+                        );
+                    }
+                );
+                break;
+            }
+            default: {
+                throw new IllegalStateException("Unknown portal type " + type);
+            }
+        }
+    }
+
+    public boolean canPortalAsync(boolean considerPassengers) {
+        return this.canPortalAsync(considerPassengers, false);
+    }
+
+    protected boolean canPortalAsync(boolean considerPassengers, boolean skipPassengerCheck) {
+        if (considerPassengers) {
+            if (!skipPassengerCheck && this.isPassenger()) {
+                return false;
+            }
+        } else {
+            if (this.isVehicle() || (!skipPassengerCheck && this.isPassenger())) {
+                return false;
+            }
+        }
+        this.getBukkitEntity(); // force bukkit entity to be created before TPing
+        if (!this.canTeleportAsync() || !this.canChangeDimensions() || this.isOnPortalCooldown()) {
+            return false;
+        }
+        if (considerPassengers) {
+            for (Entity entity : this.passengers) {
+                if (!entity.canPortalAsync(true, true)) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    protected void prePortalLogic(ServerLevel origin, ServerLevel destination, PortalType type) {
+
+    }
+
+    protected boolean portalToAsync(ServerLevel destination, boolean takePassengers,
+                                    PortalType type, java.util.function.Consumer<Entity> teleportComplete) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot portal entity async");
+        if (!this.canPortalAsync(takePassengers)) {
+            return false;
+        }
+
+        Vec3 initialPosition = this.position();
+        ChunkPos initialPositionChunk = new ChunkPos(
+            io.papermc.paper.util.CoordinateUtils.getChunkX(initialPosition),
+            io.papermc.paper.util.CoordinateUtils.getChunkZ(initialPosition)
+        );
+
+        // first, remove entity/passengers from world
+        EntityTreeNode passengerTree = this.detachPassengers();
+        List<EntityTreeNode> fullPassengerTree = passengerTree.getFullTree();
+        ServerLevel originWorld = (ServerLevel)this.level;
+
+        for (EntityTreeNode node : fullPassengerTree) {
+            node.root.preChangeDimension();
+            node.root.prePortalLogic(originWorld, destination, type);
+        }
+
+        for (EntityTreeNode node : fullPassengerTree) {
+            // we will update pos/rot/speed later
+            node.root = node.root.transformForAsyncTeleport(destination, null, null, null, null);
+            // set portal cooldown
+            node.root.setPortalCooldown();
+        }
+
+        // ensure the region is always ticking in case of a shutdown
+        // otherwise, the shutdown will not be able to complete the shutdown as it requires a ticking region
+        Long teleportHoldId = Long.valueOf(TELEPORT_HOLD_TICKET_GEN.getAndIncrement());
+        originWorld.chunkSource.addTicketAtLevel(
+            TicketType.TELEPORT_HOLD_TICKET, initialPositionChunk,
+            io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+            teleportHoldId
+        );
+
+        ServerLevel.PendingTeleport beforeFindDestination = new ServerLevel.PendingTeleport(passengerTree, initialPosition);
+        originWorld.pushPendingTeleport(beforeFindDestination);
+
+        ca.spottedleaf.concurrentutil.completable.Completable<PortalInfo> portalInfoCompletable
+            = new ca.spottedleaf.concurrentutil.completable.Completable<>();
+
+        portalInfoCompletable.addWaiter((PortalInfo info, Throwable throwable) -> {
+            if (!originWorld.removePendingTeleport(beforeFindDestination)) {
+                // the shutdown thread has placed us back into the origin world at the original position
+                // we just have to abandon this teleport to prevent duplication
+                return;
+            }
+            originWorld.chunkSource.removeTicketAtLevel(
+                TicketType.TELEPORT_HOLD_TICKET, initialPositionChunk,
+                io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.MAX_TICKET_LEVEL,
+                teleportHoldId
+            );
+            // adjust passenger tree to final pos
+            for (EntityTreeNode node : fullPassengerTree) {
+                node.root.transform(info.pos, Float.valueOf(info.yRot), Float.valueOf(info.xRot), info.speed);
+            }
+
+            // place
+            passengerTree.root.placeInAsync(
+                originWorld, destination, Entity.TELEPORT_FLAG_LOAD_CHUNK | (takePassengers ? Entity.TELEPORT_FLAG_TELEPORT_PASSENGERS : 0L),
+                passengerTree, teleportComplete
+            );
+        });
+
+
+        passengerTree.root.findOrCreatePortalAsync(originWorld, destination, type, portalInfoCompletable);
+
+        return true;
+    }
+    // Folia end - region threading
+
     @Nullable
     public Entity changeDimension(ServerLevel destination) {
         // CraftBukkit start
@@ -3643,6 +4415,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
     @Nullable
     public Entity teleportTo(ServerLevel worldserver, Vec3 location) {
+        // Folia start - region threading
+        if (true) {
+            throw new UnsupportedOperationException("Must use teleportAsync while in region threading");
+        }
+        // Folia end - region threading
         // CraftBukkit end
         // Paper start - Fix item duplication and teleport issues
         if (!this.isAlive() || !this.valid) {
@@ -3735,6 +4512,12 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         }
     }
 
+    // Folia start - region threading - move inventory clearing until after the dimension change
+    protected void postRemoveAfterChangingDimensions() {
+
+    }
+    // Folia end - region threading - move inventory clearing until after the dimension change
+
     protected void removeAfterChangingDimensions() {
         this.setRemoved(Entity.RemovalReason.CHANGED_DIMENSION, null); // CraftBukkit - add Bukkit remove cause
     }
@@ -4669,7 +5452,8 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
             }
         }
         // Paper end - Fix MC-4
-        if (this.position.x != x || this.position.y != y || this.position.z != z) {
+        boolean posChanged = this.position.x != x || this.position.y != y || this.position.z != z; // Folia - region threading
+        if (posChanged) { // Folia - region threading
             synchronized (this.posLock) { // Paper
             this.position = new Vec3(x, y, z);
             } // Paper
@@ -4690,7 +5474,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
 
         // Paper start - Block invalid positions and bounding box; don't allow desync of pos and AABB
         // hanging has its own special logic
-        if (!(this instanceof net.minecraft.world.entity.decoration.HangingEntity) && (forceBoundingBoxUpdate || this.position.x != x || this.position.y != y || this.position.z != z)) {
+        if (!(this instanceof net.minecraft.world.entity.decoration.HangingEntity) && (forceBoundingBoxUpdate || posChanged)) {
             this.setBoundingBox(this.makeBoundingBox());
         }
         // Paper end - Block invalid positions and bounding box
@@ -4777,6 +5561,12 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         return this.removalReason != null;
     }
 
+    // Folia start - region threading
+    public final boolean hasNullCallback() {
+        return this.levelCallback == EntityInLevelCallback.NULL;
+    }
+    // Folia end - region threading
+
     @Nullable
     public Entity.RemovalReason getRemovalReason() {
         return this.removalReason;
@@ -4800,6 +5590,9 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         CraftEventFactory.callEntityRemoveEvent(this, cause);
         // CraftBukkit end
         final boolean alreadyRemoved = this.removalReason != null; // Paper - Folia schedulers
+        // Folia start - region threading
+        this.preRemove(entity_removalreason);
+        // Folia end - region threading
         if (this.removalReason == null) {
             this.removalReason = entity_removalreason;
         }
@@ -4822,6 +5615,10 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
         this.removalReason = null;
     }
 
+    // Folia start - region threading
+    protected void preRemove(Entity.RemovalReason reason) {}
+    // Folia end - region threading
+
     // Paper start - Folia schedulers
     /**
      * Invoked only when the entity is truly removed from the server, never to be added to any world.
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index e9bb7feb591032904516d1b9374f486d8a7d066c..73e0c2ec5ab8cf54767755f31d1a8d0a168ee46f 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -246,7 +246,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
     private Optional<BlockPos> lastClimbablePos;
     @Nullable
     private DamageSource lastDamageSource;
-    private long lastDamageStamp;
+    private long lastDamageStamp = Long.MIN_VALUE; // Folia - region threading
     protected int autoSpinAttackTicks;
     private float swimAmount;
     private float swimAmountO;
@@ -276,6 +276,21 @@ public abstract class LivingEntity extends Entity implements Attackable {
         ++this.noActionTime; // Above all the floats
     }
     // Spigot end
+    // Folia start - region threading
+    @Override
+    public void updateTicks(long fromTickOffset, long fromRedstoneTimeOffset) {
+        super.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+        if (this.lastDamageStamp != Long.MIN_VALUE) {
+            this.lastDamageStamp += fromRedstoneTimeOffset;
+        }
+    }
+
+    @Override
+    protected void resetStoredPositions() {
+        super.resetStoredPositions();
+        this.lastClimbablePos = Optional.empty();
+    }
+    // Folia end - region threading
 
     protected LivingEntity(EntityType<? extends LivingEntity> type, Level world) {
         super(type, world);
@@ -481,7 +496,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
         if (this.isDeadOrDying() && this.level().shouldTickDeath(this)) {
             this.tickDeath();
-        }
+        } else { this.broadcastedDeath = false; } // Folia - region threading
 
         if (this.lastHurtByPlayerTime > 0) {
             --this.lastHurtByPlayerTime;
@@ -627,11 +642,14 @@ public abstract class LivingEntity extends Entity implements Attackable {
         return true;
     }
 
+    public boolean broadcastedDeath = false; // Folia - region threading
     protected void tickDeath() {
         ++this.deathTime;
-        if (this.deathTime >= 20 && !this.level().isClientSide() && !this.isRemoved()) {
+        if (this.deathTime >= 20 && !this.level().isClientSide() && !this.isRemoved() && !this.broadcastedDeath) { // Folia - region threading
             this.level().broadcastEntityEvent(this, (byte) 60);
-            this.remove(Entity.RemovalReason.KILLED, EntityRemoveEvent.Cause.DEATH); // CraftBukkit - add Bukkit remove cause
+            this.broadcastedDeath = true; // Folia - region threading - death has been broadcasted
+            if (!(this instanceof ServerPlayer)) this.remove(Entity.RemovalReason.KILLED, EntityRemoveEvent.Cause.DEATH); // CraftBukkit - add Bukkit remove cause  // Folia - region threading - don't remove, we want the tick scheduler to be running
+            if ((this instanceof ServerPlayer)) this.unRide(); // Folia - region threading - unmount player when dead
         }
 
     }
@@ -860,9 +878,9 @@ public abstract class LivingEntity extends Entity implements Attackable {
         }
 
         this.hurtTime = nbt.getShort("HurtTime");
-        this.deathTime = nbt.getShort("DeathTime");
+        this.deathTime = nbt.getShort("DeathTime"); this.broadcastedDeath = false; // Folia - region threading
         this.lastHurtByMobTimestamp = nbt.getInt("HurtByTimestamp");
-        if (nbt.contains("Team", 8)) {
+        if (false && nbt.contains("Team", 8)) { // Folia start - region threading
             String s = nbt.getString("Team");
             PlayerTeam scoreboardteam = this.level().getScoreboard().getPlayerTeam(s);
             if (!this.level().paperConfig().scoreboards.allowNonPlayerEntitiesOnScoreboards && !(this instanceof net.minecraft.world.entity.player.Player)) { scoreboardteam = null; } // Paper - Perf: Disable Scoreboards for non players by default
@@ -1149,6 +1167,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
     public boolean addEffect(MobEffectInstance mobeffect, @Nullable Entity entity, EntityPotionEffectEvent.Cause cause, boolean fireEvent) {
         // Paper end - Don't fire sync event during generation
         // org.spigotmc.AsyncCatcher.catchOp("effect add"); // Spigot // Paper - move to API
+        if (!this.hasNullCallback()) io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot add effects to entities asynchronously"); // Folia - region threading
         if (this.isTickingEffects) {
             this.effectsToProcess.add(new ProcessableEffect(mobeffect, cause));
             return true;
@@ -1573,7 +1592,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
             if (flag2) {
                 this.lastDamageSource = source;
-                this.lastDamageStamp = this.level().getGameTime();
+                this.lastDamageStamp = this.level().getRedstoneGameTime(); // Folia - region threading
             }
 
             if (this instanceof ServerPlayer) {
@@ -1656,7 +1675,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
     @Nullable
     public DamageSource getLastDamageSource() {
-        if (this.level().getGameTime() - this.lastDamageStamp > 40L) {
+        if (this.level().getRedstoneGameTime() - this.lastDamageStamp > 40L || this.lastDamageStamp == Long.MIN_VALUE) { // Folia - region threading
             this.lastDamageSource = null;
         }
 
@@ -2359,7 +2378,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
     @Nullable
     public LivingEntity getKillCredit() {
-        return (LivingEntity) (this.lastHurtByPlayer != null ? this.lastHurtByPlayer : (this.lastHurtByMob != null ? this.lastHurtByMob : null));
+        return (LivingEntity) (this.lastHurtByPlayer != null && io.papermc.paper.util.TickThread.isTickThreadFor(this.lastHurtByPlayer) ? this.lastHurtByPlayer : (this.lastHurtByMob != null && io.papermc.paper.util.TickThread.isTickThreadFor(this.lastHurtByMob) ? this.lastHurtByMob : null)); // Folia - region threading
     }
 
     public final float getMaxHealth() {
@@ -2437,7 +2456,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
         this.hurt(this.damageSources().generic(), 0.0F);
         this.lastDamageSource = damageSource;
-        this.lastDamageStamp = this.level().getGameTime();
+        this.lastDamageStamp = this.level().getRedstoneGameTime(); // Folia - region threading
     }
 
     @Override
@@ -3502,7 +3521,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
         this.pushEntities();
         this.level().getProfiler().pop();
         // Paper start - Add EntityMoveEvent
-        if (((ServerLevel) this.level()).hasEntityMoveEvent && !(this instanceof net.minecraft.world.entity.player.Player)) {
+        if (((ServerLevel) this.level()).getCurrentWorldData().hasEntityMoveEvent && !(this instanceof net.minecraft.world.entity.player.Player)) { // Folia - region threading
             if (this.xo != this.getX() || this.yo != this.getY() || this.zo != this.getZ() || this.yRotO != this.getYRot() || this.xRotO != this.getXRot()) {
                 Location from = new Location(this.level().getWorld(), this.xo, this.yo, this.zo, this.yRotO, this.xRotO);
                 Location to = new Location(this.level().getWorld(), this.getX(), this.getY(), this.getZ(), this.getYRot(), this.getXRot());
@@ -4195,7 +4214,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
         BlockPos blockposition = BlockPos.containing(d0, d1, d2);
         Level world = this.level();
 
-        if (world.hasChunkAt(blockposition)) {
+        if (io.papermc.paper.util.TickThread.isTickThreadFor((ServerLevel)world, blockposition) && world.hasChunkAt(blockposition)) { // Folia - region threading
             boolean flag2 = false;
 
             while (!flag2 && blockposition.getY() > world.getMinBuildHeight()) {
diff --git a/src/main/java/net/minecraft/world/entity/Mob.java b/src/main/java/net/minecraft/world/entity/Mob.java
index d2c92df28475f0a32a0134324eb0a5609a9afb99..3228d15fc21fec08e8683f96c829935a1de6cf45 100644
--- a/src/main/java/net/minecraft/world/entity/Mob.java
+++ b/src/main/java/net/minecraft/world/entity/Mob.java
@@ -138,6 +138,14 @@ public abstract class Mob extends LivingEntity implements Targeting {
 
     public boolean aware = true; // CraftBukkit
 
+    // Folia start - region threading
+    @Override
+    public void preChangeDimension() {
+        super.preChangeDimension();
+        this.dropLeash(true, true);
+    }
+    // Folia end - region threading
+
     protected Mob(EntityType<? extends Mob> type, Level world) {
         super(type, world);
         this.handItems = NonNullList.withSize(2, ItemStack.EMPTY);
@@ -289,9 +297,21 @@ public abstract class Mob extends LivingEntity implements Targeting {
     @Nullable
     @Override
     public LivingEntity getTarget() {
+        // Folia start - region threading
+        if (this.target != null && (!io.papermc.paper.util.TickThread.isTickThreadFor(this.target) || this.target.isRemoved())) {
+            this.target = null;
+            return null;
+        }
+        // Folia end - region threading
         return this.target;
     }
 
+    // Folia start - region threading
+    public LivingEntity getTargetRaw() {
+        return this.target;
+    }
+    // Folia end - region threading
+
     public org.bukkit.craftbukkit.entity.CraftMob getBukkitMob() { return (org.bukkit.craftbukkit.entity.CraftMob) super.getBukkitEntity(); } // Paper
     public void setTarget(@Nullable LivingEntity target) {
         // CraftBukkit start - fire event
@@ -299,7 +319,7 @@ public abstract class Mob extends LivingEntity implements Targeting {
     }
 
     public boolean setTarget(LivingEntity entityliving, EntityTargetEvent.TargetReason reason, boolean fireEvent) {
-        if (this.getTarget() == entityliving) return false;
+        if (this.getTargetRaw() == entityliving) return false; // Folia - region threading
         if (fireEvent) {
             if (reason == EntityTargetEvent.TargetReason.UNKNOWN && this.getTarget() != null && entityliving == null) {
                 reason = this.getTarget().isAlive() ? EntityTargetEvent.TargetReason.FORGOT_TARGET : EntityTargetEvent.TargetReason.TARGET_DIED;
@@ -909,7 +929,7 @@ public abstract class Mob extends LivingEntity implements Targeting {
         this.level().getProfiler().push("sensing");
         this.sensing.tick();
         this.level().getProfiler().pop();
-        int i = this.level().getServer().getTickCount() + this.getId();
+        int i = this.tickCount + this.getId(); // Folia - region threading
 
         if (i % 2 != 0 && this.tickCount > 1) {
             this.level().getProfiler().push("targetSelector");
@@ -1759,6 +1779,17 @@ public abstract class Mob extends LivingEntity implements Targeting {
         this.goalSelector.removeAllGoals(predicate);
     }
 
+    // Folia start - region threading - move inventory clearing until after the dimension change
+    @Override
+    protected void postRemoveAfterChangingDimensions() {
+        this.getAllSlots().forEach((itemstack) -> {
+            if (!itemstack.isEmpty()) {
+                itemstack.setCount(0);
+            }
+        });
+    }
+    // Folia end - region threading - move inventory clearing until after the dimension change
+
     @Override
     protected void removeAfterChangingDimensions() {
         super.removeAfterChangingDimensions();
@@ -1767,12 +1798,7 @@ public abstract class Mob extends LivingEntity implements Targeting {
         this.level().getCraftServer().getPluginManager().callEvent(event); // CraftBukkit
         this.dropLeash(true, event.isDropLeash());
         // Paper end - Expand EntityUnleashEvent
-        this.getAllSlots().forEach((itemstack) -> {
-            if (!itemstack.isEmpty()) {
-                itemstack.setCount(0);
-            }
-
-        });
+        // Folia - region threading - move inventory clearing until after the dimension change - move into postRemoveAfterChangingDimensions
     }
 
     @Nullable
diff --git a/src/main/java/net/minecraft/world/entity/ai/Brain.java b/src/main/java/net/minecraft/world/entity/ai/Brain.java
index af6f91c66e9cc7e0d491e6efed992a140947155e..d4e6198fdfbefe54e374479a1f1d835ab98ce93a 100644
--- a/src/main/java/net/minecraft/world/entity/ai/Brain.java
+++ b/src/main/java/net/minecraft/world/entity/ai/Brain.java
@@ -424,9 +424,17 @@ public class Brain<E extends LivingEntity> {
     }
 
     public void stopAll(ServerLevel world, E entity) {
+        // Folia start - region threading
+        List<BehaviorControl<? super E>> behaviors = this.getRunningBehaviors();
+        if (behaviors.isEmpty()) {
+            // avoid calling getGameTime, as this may be called while portalling an entity - which will cause
+            // the world data retrieval to fail
+            return;
+        }
+        // Folia end - region threading
         long l = entity.level().getGameTime();
 
-        for (BehaviorControl<? super E> behaviorControl : this.getRunningBehaviors()) {
+        for (BehaviorControl<? super E> behaviorControl : behaviors) { // Folia - region threading
             behaviorControl.doStop(world, entity, l);
         }
     }
diff --git a/src/main/java/net/minecraft/world/entity/ai/behavior/PoiCompetitorScan.java b/src/main/java/net/minecraft/world/entity/ai/behavior/PoiCompetitorScan.java
index 7302d397d39d8400527ab2da4adaf8d792256749..cb92900d5528b953ec4c9f071a75a064987b9a9f 100644
--- a/src/main/java/net/minecraft/world/entity/ai/behavior/PoiCompetitorScan.java
+++ b/src/main/java/net/minecraft/world/entity/ai/behavior/PoiCompetitorScan.java
@@ -19,6 +19,11 @@ public class PoiCompetitorScan {
                         context,
                         (jobSite, mobs) -> (world, entity, time) -> {
                                 GlobalPos globalPos = context.get(jobSite);
+                                // Folia start - region threading
+                                if (globalPos.dimension() != world.dimension() || !io.papermc.paper.util.TickThread.isTickThreadFor(world, globalPos.pos())) {
+                                    return true;
+                                }
+                                // Folia end - region threading
                                 world.getPoiManager()
                                     .getType(globalPos.pos())
                                     .ifPresent(
diff --git a/src/main/java/net/minecraft/world/entity/ai/goal/FollowOwnerGoal.java b/src/main/java/net/minecraft/world/entity/ai/goal/FollowOwnerGoal.java
index c0da573e3818a1dd2c1ef5a61c7cb34934b0a252..d34a3018264ec196ef57151af3c1d584b0576c68 100644
--- a/src/main/java/net/minecraft/world/entity/ai/goal/FollowOwnerGoal.java
+++ b/src/main/java/net/minecraft/world/entity/ai/goal/FollowOwnerGoal.java
@@ -70,7 +70,7 @@ public class FollowOwnerGoal extends Goal {
 
     @Override
     public boolean canContinueToUse() {
-        return this.navigation.isDone() ? false : (this.unableToMove() ? false : this.tamable.distanceToSqr((Entity) this.owner) > (double) (this.stopDistance * this.stopDistance));
+        return this.navigation.isDone() ? false : (this.unableToMove() ? false : (this.owner.level() == this.level && this.tamable.distanceToSqr((Entity) this.owner) > (double) (this.stopDistance * this.stopDistance))); // Folia - region threading - check level
     }
 
     private boolean unableToMove() {
@@ -96,7 +96,7 @@ public class FollowOwnerGoal extends Goal {
         if (this.tamable.distanceToSqr(this.owner) <= 16 * 16) this.tamable.getLookControl().setLookAt(this.owner, 10.0F, (float) this.tamable.getMaxHeadXRot()); // Paper - Limit pet look distance
         if (--this.timeToRecalcPath <= 0) {
             this.timeToRecalcPath = this.adjustedTickDelay(10);
-            if (this.tamable.distanceToSqr((Entity) this.owner) >= 144.0D) {
+            if (!io.papermc.paper.util.TickThread.isTickThreadFor(this.owner) || this.tamable.distanceToSqr((Entity) this.owner) >= 144.0D) { // Folia - region threading - required in case the player suddenly moves into another dimension
                 this.teleportToOwner();
             } else {
                 this.navigation.moveTo((Entity) this.owner, this.speedModifier);
@@ -107,6 +107,11 @@ public class FollowOwnerGoal extends Goal {
 
     private void teleportToOwner() {
         BlockPos blockposition = this.owner.blockPosition();
+        // Folia start - region threading
+        if (this.owner.isRemoved() || this.owner.level() != level) {
+            return;
+        }
+        // Folia end - region threading
 
         for (int i = 0; i < 10; ++i) {
             int j = this.randomIntInclusive(-3, 3);
@@ -133,7 +138,21 @@ public class FollowOwnerGoal extends Goal {
                 return false;
             }
             Location to = event.getTo();
-            this.tamable.moveTo(to.getX(), to.getY(), to.getZ(), to.getYaw(), to.getPitch());
+            // Folia start - region threading - can't teleport here, we may be removed by teleport logic - delay until next tick
+            // also, use teleportAsync so that crossing region boundaries will not blow up
+            Location finalTo = to;
+            this.tamable.getBukkitEntity().taskScheduler.schedule((TamableAnimal nmsEntity) -> {
+                if (nmsEntity.level() == FollowOwnerGoal.this.level) {
+                    nmsEntity.teleportAsync(
+                        (net.minecraft.server.level.ServerLevel)nmsEntity.level(),
+                        new net.minecraft.world.phys.Vec3(finalTo.getX(), finalTo.getY(), finalTo.getZ()),
+                        Float.valueOf(finalTo.getYaw()), Float.valueOf(finalTo.getPitch()),
+                        net.minecraft.world.phys.Vec3.ZERO, org.bukkit.event.player.PlayerTeleportEvent.TeleportCause.UNKNOWN, Entity.TELEPORT_FLAG_LOAD_CHUNK,
+                        null
+                    );
+                }
+            }, null, 1L);
+            // Folia start - region threading - can't teleport here, we may be removed by teleport logic - delay until next tick
             // CraftBukkit end
             this.navigation.stop();
             return true;
diff --git a/src/main/java/net/minecraft/world/entity/ai/navigation/GroundPathNavigation.java b/src/main/java/net/minecraft/world/entity/ai/navigation/GroundPathNavigation.java
index 74ae984ac41bcdd2cc45f1bec461cdc5f69977c6..a978b9c3edb64a5a0b91166b20fa28a3d9e8b2f8 100644
--- a/src/main/java/net/minecraft/world/entity/ai/navigation/GroundPathNavigation.java
+++ b/src/main/java/net/minecraft/world/entity/ai/navigation/GroundPathNavigation.java
@@ -42,6 +42,11 @@ public class GroundPathNavigation extends PathNavigation {
 
     @Override
     public Path createPath(BlockPos target, @javax.annotation.Nullable Entity entity, int distance) { // Paper - EntityPathfindEvent
+        // Folia start - region threading
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)this.level, target)) {
+            return null;
+        }
+        // Folia end - region threading
         LevelChunk levelChunk = this.level
             .getChunkSource()
             .getChunkNow(SectionPos.blockToSectionCoord(target.getX()), SectionPos.blockToSectionCoord(target.getZ()));
diff --git a/src/main/java/net/minecraft/world/entity/ai/navigation/PathNavigation.java b/src/main/java/net/minecraft/world/entity/ai/navigation/PathNavigation.java
index e3a7eaf31ab19cc9f23a0c87649b74bb42976cb4..1a364f9857608413813c8c2ca5b71ec8c90fe8b6 100644
--- a/src/main/java/net/minecraft/world/entity/ai/navigation/PathNavigation.java
+++ b/src/main/java/net/minecraft/world/entity/ai/navigation/PathNavigation.java
@@ -80,11 +80,11 @@ public abstract class PathNavigation {
     }
 
     public void recomputePath() {
-        if (this.level.getGameTime() - this.timeLastRecompute > 20L) {
+        if (this.tick - this.timeLastRecompute > 20L) { // Folia - region threading
             if (this.targetPos != null) {
                 this.path = null;
                 this.path = this.createPath(this.targetPos, this.reachRange);
-                this.timeLastRecompute = this.level.getGameTime();
+                this.timeLastRecompute = this.tick; // Folia - region threading
                 this.hasDelayedRecomputation = false;
             }
         } else {
@@ -199,7 +199,7 @@ public abstract class PathNavigation {
 
     public boolean moveTo(Entity entity, double speed) {
         // Paper start - Perf: Optimise pathfinding
-        if (this.pathfindFailures > 10 && this.path == null && net.minecraft.server.MinecraftServer.currentTick < this.lastFailure + 40) {
+        if (this.pathfindFailures > 10 && this.path == null && this.tick < this.lastFailure + 40) { // Folia - region threading
             return false;
         }
         // Paper end - Perf: Optimise pathfinding
@@ -211,7 +211,7 @@ public abstract class PathNavigation {
             return true;
         } else {
             this.pathfindFailures++;
-            this.lastFailure = net.minecraft.server.MinecraftServer.currentTick;
+            this.lastFailure = this.tick; // Folia - region threading
             return false;
         }
         // Paper end - Perf: Optimise pathfinding
diff --git a/src/main/java/net/minecraft/world/entity/ai/sensing/TemptingSensor.java b/src/main/java/net/minecraft/world/entity/ai/sensing/TemptingSensor.java
index e3242cf9a6ad51a23c5781142198dec30c8f376d..f32f5982ceb368b240062b9b8ac0141be59e2f1e 100644
--- a/src/main/java/net/minecraft/world/entity/ai/sensing/TemptingSensor.java
+++ b/src/main/java/net/minecraft/world/entity/ai/sensing/TemptingSensor.java
@@ -37,7 +37,7 @@ public class TemptingSensor extends Sensor<PathfinderMob> {
 
     protected void doTick(ServerLevel world, PathfinderMob entity) {
         Brain<?> behaviorcontroller = entity.getBrain();
-        Stream<net.minecraft.server.level.ServerPlayer> stream = world.players().stream().filter(EntitySelector.NO_SPECTATORS).filter((entityplayer) -> { // CraftBukkit - decompile error
+        Stream<net.minecraft.server.level.ServerPlayer> stream = world.getLocalPlayers().stream().filter(EntitySelector.NO_SPECTATORS).filter((entityplayer) -> { // CraftBukkit - decompile error // Folia - region threading
             return TemptingSensor.TEMPT_TARGETING.test(entity, entityplayer);
         }).filter((entityplayer) -> {
             return entity.closerThan(entityplayer, 10.0D);
diff --git a/src/main/java/net/minecraft/world/entity/ai/village/VillageSiege.java b/src/main/java/net/minecraft/world/entity/ai/village/VillageSiege.java
index 2b5b2869589991be37a4f128faabbff50e661470..c8d4878a0574a603bbb4bce45d1fb4d84b7ac6ce 100644
--- a/src/main/java/net/minecraft/world/entity/ai/village/VillageSiege.java
+++ b/src/main/java/net/minecraft/world/entity/ai/village/VillageSiege.java
@@ -22,62 +22,66 @@ import org.slf4j.Logger;
 public class VillageSiege implements CustomSpawner {
 
     private static final Logger LOGGER = LogUtils.getLogger();
-    private boolean hasSetupSiege;
-    private VillageSiege.State siegeState;
-    private int zombiesToSpawn;
-    private int nextSpawnTime;
-    private int spawnX;
-    private int spawnY;
-    private int spawnZ;
+    // Folia - region threading
 
     public VillageSiege() {
-        this.siegeState = VillageSiege.State.SIEGE_DONE;
+        // Folia - region threading
     }
 
     @Override
     public int tick(ServerLevel world, boolean spawnMonsters, boolean spawnAnimals) {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+        // Folia start - region threading
+        // check if the spawn pos is no longer owned by this region
+        if (worldData.villageSiegeState.siegeState != State.SIEGE_DONE
+            && !io.papermc.paper.util.TickThread.isTickThreadFor(world, worldData.villageSiegeState.spawnX >> 4, worldData.villageSiegeState.spawnZ >> 4, 8)) {
+            // can't spawn here, just re-set
+            worldData.villageSiegeState = new io.papermc.paper.threadedregions.RegionizedWorldData.VillageSiegeState();
+        }
+        // Folia end - region threading
         if (!world.isDay() && spawnMonsters) {
             float f = world.getTimeOfDay(0.0F);
 
             if ((double) f == 0.5D) {
-                this.siegeState = world.random.nextInt(10) == 0 ? VillageSiege.State.SIEGE_TONIGHT : VillageSiege.State.SIEGE_DONE;
+                worldData.villageSiegeState.siegeState = world.random.nextInt(10) == 0 ? VillageSiege.State.SIEGE_TONIGHT : VillageSiege.State.SIEGE_DONE; // Folia - region threading
             }
 
-            if (this.siegeState == VillageSiege.State.SIEGE_DONE) {
+            if (worldData.villageSiegeState.siegeState == VillageSiege.State.SIEGE_DONE) { // Folia - region threading
                 return 0;
             } else {
-                if (!this.hasSetupSiege) {
+                if (!worldData.villageSiegeState.hasSetupSiege) { // Folia - region threading
                     if (!this.tryToSetupSiege(world)) {
                         return 0;
                     }
 
-                    this.hasSetupSiege = true;
+                    worldData.villageSiegeState.hasSetupSiege = true; // Folia - region threading
                 }
 
-                if (this.nextSpawnTime > 0) {
-                    --this.nextSpawnTime;
+                if (worldData.villageSiegeState.nextSpawnTime > 0) { // Folia - region threading
+                    --worldData.villageSiegeState.nextSpawnTime; // Folia - region threading
                     return 0;
                 } else {
-                    this.nextSpawnTime = 2;
-                    if (this.zombiesToSpawn > 0) {
+                    worldData.villageSiegeState.nextSpawnTime = 2; // Folia - region threading
+                    if (worldData.villageSiegeState.zombiesToSpawn > 0) { // Folia - region threading
                         this.trySpawn(world);
-                        --this.zombiesToSpawn;
+                        --worldData.villageSiegeState.zombiesToSpawn; // Folia - region threading
                     } else {
-                        this.siegeState = VillageSiege.State.SIEGE_DONE;
+                        worldData.villageSiegeState.siegeState = VillageSiege.State.SIEGE_DONE; // Folia - region threading
                     }
 
                     return 1;
                 }
             }
         } else {
-            this.siegeState = VillageSiege.State.SIEGE_DONE;
-            this.hasSetupSiege = false;
+            worldData.villageSiegeState.siegeState = VillageSiege.State.SIEGE_DONE; // Folia - region threading
+            worldData.villageSiegeState.hasSetupSiege = false; // Folia - region threading
             return 0;
         }
     }
 
     private boolean tryToSetupSiege(ServerLevel world) {
-        Iterator iterator = world.players().iterator();
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+        Iterator iterator = world.getLocalPlayers().iterator(); // Folia - region threading
 
         while (iterator.hasNext()) {
             Player entityhuman = (Player) iterator.next();
@@ -89,12 +93,12 @@ public class VillageSiege implements CustomSpawner {
                     for (int i = 0; i < 10; ++i) {
                         float f = world.random.nextFloat() * 6.2831855F;
 
-                        this.spawnX = blockposition.getX() + Mth.floor(Mth.cos(f) * 32.0F);
-                        this.spawnY = blockposition.getY();
-                        this.spawnZ = blockposition.getZ() + Mth.floor(Mth.sin(f) * 32.0F);
-                        if (this.findRandomSpawnPos(world, new BlockPos(this.spawnX, this.spawnY, this.spawnZ)) != null) {
-                            this.nextSpawnTime = 0;
-                            this.zombiesToSpawn = 20;
+                        worldData.villageSiegeState.spawnX = blockposition.getX() + Mth.floor(Mth.cos(f) * 32.0F); // Folia - region threading
+                        worldData.villageSiegeState.spawnY = blockposition.getY(); // Folia - region threading
+                        worldData.villageSiegeState.spawnZ = blockposition.getZ() + Mth.floor(Mth.sin(f) * 32.0F); // Folia - region threading
+                        if (this.findRandomSpawnPos(world, new BlockPos(worldData.villageSiegeState.spawnX, worldData.villageSiegeState.spawnY, worldData.villageSiegeState.spawnZ)) != null) { // Folia - region threading
+                            worldData.villageSiegeState.nextSpawnTime = 0; // Folia - region threading
+                            worldData.villageSiegeState.zombiesToSpawn = 20; // Folia - region threading
                             break;
                         }
                     }
@@ -108,13 +112,15 @@ public class VillageSiege implements CustomSpawner {
     }
 
     private void trySpawn(ServerLevel world) {
-        Vec3 vec3d = this.findRandomSpawnPos(world, new BlockPos(this.spawnX, this.spawnY, this.spawnZ));
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+        Vec3 vec3d = this.findRandomSpawnPos(world, new BlockPos(worldData.villageSiegeState.spawnX, worldData.villageSiegeState.spawnY, worldData.villageSiegeState.spawnZ)); // Folia - region threading
 
         if (vec3d != null) {
             Zombie entityzombie;
 
             try {
                 entityzombie = new Zombie(world);
+                entityzombie.moveTo(vec3d.x, vec3d.y, vec3d.z, world.random.nextFloat() * 360.0F, 0.0F); // Folia - region threading - move up
                 entityzombie.finalizeSpawn(world, world.getCurrentDifficultyAt(entityzombie.blockPosition()), MobSpawnType.EVENT, (SpawnGroupData) null, (CompoundTag) null);
             } catch (Exception exception) {
                 VillageSiege.LOGGER.warn("Failed to create zombie for village siege at {}", vec3d, exception);
@@ -122,7 +128,7 @@ public class VillageSiege implements CustomSpawner {
                 return;
             }
 
-            entityzombie.moveTo(vec3d.x, vec3d.y, vec3d.z, world.random.nextFloat() * 360.0F, 0.0F);
+            // Folia - region threading - move up
             world.addFreshEntityWithPassengers(entityzombie, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.VILLAGE_INVASION); // CraftBukkit
         }
     }
@@ -143,7 +149,7 @@ public class VillageSiege implements CustomSpawner {
         return null;
     }
 
-    private static enum State {
+    public static enum State { // Folia - region threading
 
         SIEGE_CAN_ACTIVATE, SIEGE_TONIGHT, SIEGE_DONE;
 
diff --git a/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java b/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java
index 61a06706f1468a8d4cceb9fb2aae61cf56bd991d..79e9e5ece5859938ca0c86ead4c25cf5bde9da27 100644
--- a/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java
+++ b/src/main/java/net/minecraft/world/entity/ai/village/poi/PoiManager.java
@@ -48,11 +48,13 @@ public class PoiManager extends SectionStorage<PoiSection> {
     }
 
     protected void updateDistanceTracking(long section) {
+        synchronized (this.villageDistanceTracker) { // Folia - region threading
         if (this.isVillageCenter(section)) {
             this.villageDistanceTracker.setSource(section, POI_DATA_SOURCE);
         } else {
             this.villageDistanceTracker.removeSource(section);
         }
+        } // Folia - region threading
     }
     // Paper end - rewrite chunk system
 
@@ -215,8 +217,10 @@ public class PoiManager extends SectionStorage<PoiSection> {
     }
 
     public int sectionsToVillage(SectionPos pos) {
+        synchronized (this.villageDistanceTracker) { // Folia - region threading
         this.villageDistanceTracker.propagateUpdates(); // Paper - replace distance tracking util
         return convertBetweenLevels(this.villageDistanceTracker.getLevel(io.papermc.paper.util.CoordinateUtils.getChunkSectionKey(pos))); // Paper - replace distance tracking util
+        } // Folia - region threading
     }
 
     boolean isVillageCenter(long pos) {
@@ -230,7 +234,9 @@ public class PoiManager extends SectionStorage<PoiSection> {
 
     @Override
     public void tick(BooleanSupplier shouldKeepTicking) {
+        synchronized (this.villageDistanceTracker) { // Folia - region threading
         this.villageDistanceTracker.propagateUpdates(); // Paper - rewrite chunk system
+        } // Folia - region threading
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/world/entity/animal/Bee.java b/src/main/java/net/minecraft/world/entity/animal/Bee.java
index f9521a6e115f0c975a7885b024c99eae300b63bf..9f1791e60061934fc89a13258f3fab9f67f3a45c 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Bee.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Bee.java
@@ -1043,6 +1043,11 @@ public class Bee extends Animal implements NeutralMob, FlyingAnimal {
 
         @Override
         public boolean canBeeUse() {
+            // Folia start - region threading
+            if (Bee.this.hivePos != null && Bee.this.isTooFarAway(Bee.this.hivePos)) {
+                Bee.this.hivePos = null;
+            }
+            // Folia end - region threading
             return Bee.this.hivePos != null && !Bee.this.hasRestriction() && Bee.this.wantsToEnterHive() && !this.hasReachedTarget(Bee.this.hivePos) && Bee.this.level().getBlockState(Bee.this.hivePos).is(BlockTags.BEEHIVES);
         }
 
@@ -1159,6 +1164,11 @@ public class Bee extends Animal implements NeutralMob, FlyingAnimal {
 
         @Override
         public boolean canBeeUse() {
+            // Folia start - region threading
+            if (Bee.this.savedFlowerPos != null && Bee.this.isTooFarAway(Bee.this.savedFlowerPos)) {
+                Bee.this.savedFlowerPos = null;
+            }
+            // Folia end - region threading
             return Bee.this.savedFlowerPos != null && !Bee.this.hasRestriction() && this.wantsToGoToKnownFlower() && Bee.this.isFlowerValid(Bee.this.savedFlowerPos) && !Bee.this.closerThan(Bee.this.savedFlowerPos, 2);
         }
 
diff --git a/src/main/java/net/minecraft/world/entity/animal/Cat.java b/src/main/java/net/minecraft/world/entity/animal/Cat.java
index f760ce7d9df79ef58f8963de3e901cba3e12fcaa..03bd7038bda7bd3bf592eab39ec6d985e07e3b8d 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Cat.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Cat.java
@@ -364,7 +364,7 @@ public class Cat extends TamableAnimal implements VariantHolder<CatVariant> {
         });
         ServerLevel worldserver = world.getLevel();
 
-        if (worldserver.structureManager().getStructureWithPieceAt(this.blockPosition(), StructureTags.CATS_SPAWN_AS_BLACK, world).isValid()) { // Paper - Fix swamp hut cat generation deadlock
+        if (world.structureManager().getStructureWithPieceAt(this.blockPosition(), StructureTags.CATS_SPAWN_AS_BLACK).isValid()) { // Paper - Fix swamp hut cat generation deadlock // Folia - region threading - properly fix this
             this.setVariant((CatVariant) BuiltInRegistries.CAT_VARIANT.getOrThrow(CatVariant.ALL_BLACK));
             this.setPersistenceRequired();
         }
diff --git a/src/main/java/net/minecraft/world/entity/decoration/ItemFrame.java b/src/main/java/net/minecraft/world/entity/decoration/ItemFrame.java
index c34701f95580e4cf45fe086115563127432a28c5..fe95aa9389f7d11e1380445a1eeca50cae549edb 100644
--- a/src/main/java/net/minecraft/world/entity/decoration/ItemFrame.java
+++ b/src/main/java/net/minecraft/world/entity/decoration/ItemFrame.java
@@ -298,8 +298,10 @@ public class ItemFrame extends HangingEntity {
             MapItemSavedData worldmap = MapItem.getSavedData(i, this.level());
 
             if (worldmap != null) {
+                synchronized (worldmap) { // Folia - make map data thread-safe
                 worldmap.removedFromFrame(this.pos, this.getId());
                 worldmap.setDirty(true);
+                } // Folia - make map data thread-safe
             }
 
         });
diff --git a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
index 29ce703a79f7893ac990ad80e0f1c1cf63546e6c..51bc4c0c8505e900cd3268048ac8cf71b2d22e6b 100644
--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
@@ -55,7 +55,7 @@ public class ItemEntity extends Entity implements TraceableEntity {
     @Nullable
     public UUID target;
     public final float bobOffs;
-    private int lastTick = MinecraftServer.currentTick - 1; // CraftBukkit
+    //private int lastTick = MinecraftServer.currentTick - 1; // CraftBukkit // Folia - region threading
     public boolean canMobPickup = true; // Paper - Item#canEntityPickup
     private int despawnRate = -1; // Paper - Alternative item-despawn-rate
     public net.kyori.adventure.util.TriState frictionState = net.kyori.adventure.util.TriState.NOT_SET; // Paper - Friction API
@@ -145,13 +145,11 @@ public class ItemEntity extends Entity implements TraceableEntity {
             this.discard(EntityRemoveEvent.Cause.DESPAWN); // CraftBukkit - add Bukkit remove cause
         } else {
             super.tick();
-            // CraftBukkit start - Use wall time for pickup and despawn timers
-            int elapsedTicks = MinecraftServer.currentTick - this.lastTick;
-            if (this.pickupDelay != 32767) this.pickupDelay -= elapsedTicks;
-            this.pickupDelay = Math.max(0, this.pickupDelay); // Paper - don't go below 0
-            if (this.age != -32768) this.age += elapsedTicks;
-            this.lastTick = MinecraftServer.currentTick;
-            // CraftBukkit end
+            // Folia start - region threading - restore original timers
+            if (this.pickupDelay > 0 && this.pickupDelay != 32767) {
+                --this.pickupDelay;
+            }
+            // Folia end - region threading - restore original timers
 
             this.xo = this.getX();
             this.yo = this.getY();
@@ -205,11 +203,11 @@ public class ItemEntity extends Entity implements TraceableEntity {
                 this.mergeWithNeighbours();
             }
 
-            /* CraftBukkit start - moved up
+            // Folia - region threading - restore original timers
             if (this.age != -32768) {
                 ++this.age;
             }
-            // CraftBukkit end */
+            // Folia - region threading - restore original timers
 
             this.hasImpulse |= this.updateInWaterStateAndDoFluidPushing();
             if (!this.level().isClientSide) {
@@ -236,13 +234,14 @@ public class ItemEntity extends Entity implements TraceableEntity {
     // Spigot start - copied from above
     @Override
     public void inactiveTick() {
-        // CraftBukkit start - Use wall time for pickup and despawn timers
-        int elapsedTicks = MinecraftServer.currentTick - this.lastTick;
-        if (this.pickupDelay != 32767) this.pickupDelay -= elapsedTicks;
-        this.pickupDelay = Math.max(0, this.pickupDelay); // Paper - don't go below 0
-        if (this.age != -32768) this.age += elapsedTicks;
-        this.lastTick = MinecraftServer.currentTick;
-        // CraftBukkit end
+        // Folia start - region threading - restore original timers
+        if (this.pickupDelay > 0 && this.pickupDelay != 32767) {
+            --this.pickupDelay;
+        }
+        if (this.age != -32768) {
+            ++this.age;
+        }
+        // Folia end - region threading - restore original timers
 
         if (!this.level().isClientSide && this.age >= this.despawnRate) { // Spigot // Paper - Alternative item-despawn-rate
             // CraftBukkit start - fire ItemDespawnEvent
@@ -549,14 +548,20 @@ public class ItemEntity extends Entity implements TraceableEntity {
         return false;
     }
 
+    // Folia start - region threading
+    @Override
+    public void postChangeDimension() {
+        super.postChangeDimension();
+        this.mergeWithNeighbours();
+    }
+    // Folia end - region threading
+
     @Nullable
     @Override
     public Entity changeDimension(ServerLevel destination) {
         Entity entity = super.changeDimension(destination);
 
-        if (!this.level().isClientSide && entity instanceof ItemEntity) {
-            ((ItemEntity) entity).mergeWithNeighbours();
-        }
+        if (entity != null) entity.postChangeDimension(); // Folia - region threading - move to post change
 
         return entity;
     }
diff --git a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
index e712bd07ea2946167782473a536e0c72fab4bccd..94d1cc62f1b0b60882541764e7272c248689b831 100644
--- a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
+++ b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
@@ -72,7 +72,7 @@ public class PrimedTnt extends Entity implements TraceableEntity {
 
     @Override
     public void tick() {
-        if (this.level().spigotConfig.maxTntTicksPerTick > 0 && ++this.level().spigotConfig.currentPrimedTnt > this.level().spigotConfig.maxTntTicksPerTick) { return; } // Spigot
+        if (this.level().spigotConfig.maxTntTicksPerTick > 0 && ++this.level().getCurrentWorldData().currentPrimedTnt > this.level().spigotConfig.maxTntTicksPerTick) { return; } // Spigot // Folia - region threading
         if (!this.isNoGravity()) {
             this.setDeltaMovement(this.getDeltaMovement().add(0.0D, -0.04D, 0.0D));
         }
@@ -114,7 +114,7 @@ public class PrimedTnt extends Entity implements TraceableEntity {
              */
             // Send position and velocity updates to nearby players on every tick while the TNT is in water.
             // This does pretty well at keeping their clients in sync with the server.
-            net.minecraft.server.level.ChunkMap.TrackedEntity ete = ((net.minecraft.server.level.ServerLevel)this.level()).getChunkSource().chunkMap.entityMap.get(this.getId());
+            net.minecraft.server.level.ChunkMap.TrackedEntity ete = this.tracker; // Folia - region threading
             if (ete != null) {
                 net.minecraft.network.protocol.game.ClientboundSetEntityMotionPacket velocityPacket = new net.minecraft.network.protocol.game.ClientboundSetEntityMotionPacket(this);
                 net.minecraft.network.protocol.game.ClientboundTeleportEntityPacket positionPacket = new net.minecraft.network.protocol.game.ClientboundTeleportEntityPacket(this);
diff --git a/src/main/java/net/minecraft/world/entity/monster/Vex.java b/src/main/java/net/minecraft/world/entity/monster/Vex.java
index f443006c1e32feee97b32312814e2447a50c45e2..3cf7fe301cb445bf1592a398a5a17b1a4d4a6dd3 100644
--- a/src/main/java/net/minecraft/world/entity/monster/Vex.java
+++ b/src/main/java/net/minecraft/world/entity/monster/Vex.java
@@ -370,7 +370,7 @@ public class Vex extends Monster implements TraceableEntity {
         public void tick() {
             BlockPos blockposition = Vex.this.getBoundOrigin();
 
-            if (blockposition == null) {
+            if (blockposition == null || !io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)Vex.this.level(), blockposition)) { // Folia - region threading
                 blockposition = Vex.this.blockPosition();
             }
 
diff --git a/src/main/java/net/minecraft/world/entity/monster/Zombie.java b/src/main/java/net/minecraft/world/entity/monster/Zombie.java
index 5c40e994007dbf46ebc12c1e6a6ca90379471b74..723ef6e7a3618c30087ce2ac50811dbe638881ec 100644
--- a/src/main/java/net/minecraft/world/entity/monster/Zombie.java
+++ b/src/main/java/net/minecraft/world/entity/monster/Zombie.java
@@ -95,7 +95,7 @@ public class Zombie extends Monster {
     private boolean canBreakDoors;
     private int inWaterTime;
     public int conversionTime;
-    private int lastTick = MinecraftServer.currentTick; // CraftBukkit - add field
+    //private int lastTick = MinecraftServer.currentTick; // CraftBukkit - add field // Folia - region threading - restore original timers
     private boolean shouldBurnInDay = true; // Paper - Add more Zombie API
 
     public Zombie(EntityType<? extends Zombie> type, Level world) {
@@ -218,10 +218,7 @@ public class Zombie extends Monster {
     public void tick() {
         if (!this.level().isClientSide && this.isAlive() && !this.isNoAi()) {
             if (this.isUnderWaterConverting()) {
-                // CraftBukkit start - Use wall time instead of ticks for conversion
-                int elapsedTicks = MinecraftServer.currentTick - this.lastTick;
-                this.conversionTime -= elapsedTicks;
-                // CraftBukkit end
+                --this.conversionTime; // Folia - region threading - restore original timers
                 if (this.conversionTime < 0) {
                     this.doUnderWaterConversion();
                 }
@@ -238,7 +235,7 @@ public class Zombie extends Monster {
         }
 
         super.tick();
-        this.lastTick = MinecraftServer.currentTick; // CraftBukkit
+        //this.lastTick = MinecraftServer.currentTick; // CraftBukkit // Folia - region threading - restore original timers
     }
 
     @Override
@@ -277,7 +274,7 @@ public class Zombie extends Monster {
     }
     // Paper end - Add more Zombie API
     public void startUnderWaterConversion(int ticksUntilWaterConversion) {
-        this.lastTick = MinecraftServer.currentTick; // CraftBukkit
+        // Folia - region threading - restore original timers
         this.conversionTime = ticksUntilWaterConversion;
         this.getEntityData().set(Zombie.DATA_DROWNED_CONVERSION_ID, true);
     }
diff --git a/src/main/java/net/minecraft/world/entity/monster/ZombieVillager.java b/src/main/java/net/minecraft/world/entity/monster/ZombieVillager.java
index 7de9d012e7416eaa0189b513a0972c846e93c4b6..9375c3732114f7a993ea96ed71531940af38c628 100644
--- a/src/main/java/net/minecraft/world/entity/monster/ZombieVillager.java
+++ b/src/main/java/net/minecraft/world/entity/monster/ZombieVillager.java
@@ -73,7 +73,7 @@ public class ZombieVillager extends Zombie implements VillagerDataHolder {
     @Nullable
     private CompoundTag tradeOffers;
     private int villagerXp;
-    private int lastTick = MinecraftServer.currentTick; // CraftBukkit - add field
+    // private int lastTick = MinecraftServer.currentTick; // CraftBukkit - add field // Folia - region threading - restore original timers
 
     public ZombieVillager(EntityType<? extends ZombieVillager> type, Level world) {
         super(type, world);
@@ -148,10 +148,7 @@ public class ZombieVillager extends Zombie implements VillagerDataHolder {
     public void tick() {
         if (!this.level().isClientSide && this.isAlive() && this.isConverting()) {
             int i = this.getConversionProgress();
-            // CraftBukkit start - Use wall time instead of ticks for villager conversion
-            int elapsedTicks = MinecraftServer.currentTick - this.lastTick;
-            i *= elapsedTicks;
-            // CraftBukkit end
+            // Folia - region threading - restore original timers
 
             this.villagerConversionTime -= i;
             if (this.villagerConversionTime <= 0) {
@@ -160,7 +157,7 @@ public class ZombieVillager extends Zombie implements VillagerDataHolder {
         }
 
         super.tick();
-        this.lastTick = MinecraftServer.currentTick; // CraftBukkit
+        // Folia - region threading - restore original timers
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/world/entity/npc/AbstractVillager.java b/src/main/java/net/minecraft/world/entity/npc/AbstractVillager.java
index 4e6c2f6b2e54a4c126e9a026b9cad05ce835ad66..d2fbeb0e4e3e681b22455b9cf2d125dcb4de0a56 100644
--- a/src/main/java/net/minecraft/world/entity/npc/AbstractVillager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/AbstractVillager.java
@@ -212,10 +212,18 @@ public abstract class AbstractVillager extends AgeableMob implements InventoryCa
         this.readInventoryFromTag(nbt);
     }
 
+    // Folia start - region threading
+    @Override
+    public void preChangeDimension() {
+        super.preChangeDimension();
+        this.stopTrading();
+    }
+    // Folia end - region threading
+
     @Nullable
     @Override
     public Entity changeDimension(ServerLevel destination) {
-        this.stopTrading();
+        this.preChangeDimension(); // Folia - region threading - move into preChangeDimension
         return super.changeDimension(destination);
     }
 
diff --git a/src/main/java/net/minecraft/world/entity/npc/CatSpawner.java b/src/main/java/net/minecraft/world/entity/npc/CatSpawner.java
index 5d1610eddcaf0cf65c726a5438b42e53bab85332..dd8e1bb65d7832d173e460eb4d8e97a8ba1ba26e 100644
--- a/src/main/java/net/minecraft/world/entity/npc/CatSpawner.java
+++ b/src/main/java/net/minecraft/world/entity/npc/CatSpawner.java
@@ -19,17 +19,18 @@ import net.minecraft.world.phys.AABB;
 
 public class CatSpawner implements CustomSpawner {
     private static final int TICK_DELAY = 1200;
-    private int nextTick;
+    //private int nextTick; // Folia - region threading
 
     @Override
     public int tick(ServerLevel world, boolean spawnMonsters, boolean spawnAnimals) {
         if (spawnAnimals && world.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING)) {
-            this.nextTick--;
-            if (this.nextTick > 0) {
+            io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+            --worldData.catSpawnerNextTick; // Folia - region threading
+            if (worldData.catSpawnerNextTick > 0) { // Folia - region threading
                 return 0;
             } else {
-                this.nextTick = 1200;
-                Player player = world.getRandomPlayer();
+                worldData.catSpawnerNextTick = 1200; // Folia - region threading
+                Player player = world.getRandomLocalPlayer(); // Folia - region threading
                 if (player == null) {
                     return 0;
                 } else {
diff --git a/src/main/java/net/minecraft/world/entity/npc/Villager.java b/src/main/java/net/minecraft/world/entity/npc/Villager.java
index 24044795d8e0f1fb15a4f2f5401f44897092f2a3..3eeff0cd8563939c656b5ded8470cab016903f25 100644
--- a/src/main/java/net/minecraft/world/entity/npc/Villager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/Villager.java
@@ -204,7 +204,7 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
         brain.setCoreActivities(ImmutableSet.of(Activity.CORE));
         brain.setDefaultActivity(Activity.IDLE);
         brain.setActiveActivityIfPossible(Activity.IDLE);
-        brain.updateActivityFromSchedule(this.level().getDayTime(), this.level().getGameTime());
+        brain.updateActivityFromSchedule(this.level().getLevelData().getDayTime(), this.level().getLevelData().getGameTime()); // Folia - region threading
     }
 
     @Override
@@ -730,6 +730,8 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
                 ServerLevel worldserver = minecraftserver.getLevel(globalpos.dimension());
 
                 if (worldserver != null) {
+                    io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue( // Folia - region threading
+                        worldserver, globalpos.pos().getX() >> 4, globalpos.pos().getZ() >> 4, () -> { // Folia - region threading
                     PoiManager villageplace = worldserver.getPoiManager();
                     Optional<Holder<PoiType>> optional = villageplace.getType(globalpos.pos());
                     BiPredicate<Villager, Holder<PoiType>> bipredicate = (BiPredicate) Villager.POI_MEMORIES.get(pos);
@@ -738,6 +740,7 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
                         villageplace.release(globalpos.pos());
                         DebugPackets.sendPoiTicketCountPacket(worldserver, globalpos.pos());
                     }
+                    }); // Folia - region threading
 
                 }
             });
diff --git a/src/main/java/net/minecraft/world/entity/npc/WanderingTraderSpawner.java b/src/main/java/net/minecraft/world/entity/npc/WanderingTraderSpawner.java
index d7bddedb19c10f62fd1f7d3128453ad706ed16be..948749a0a3ef9d06f0482bc5331a52836a6eb6a3 100644
--- a/src/main/java/net/minecraft/world/entity/npc/WanderingTraderSpawner.java
+++ b/src/main/java/net/minecraft/world/entity/npc/WanderingTraderSpawner.java
@@ -32,16 +32,14 @@ public class WanderingTraderSpawner implements CustomSpawner {
     private static final int SPAWN_CHANCE_INCREASE = 25;
     private static final int SPAWN_ONE_IN_X_CHANCE = 10;
     private static final int NUMBER_OF_SPAWN_ATTEMPTS = 10;
-    private final RandomSource random = RandomSource.create();
+    private final RandomSource random = new net.minecraft.world.entity.Entity.RandomRandomSource(); // Folia - region threading
     private final ServerLevelData serverLevelData;
-    private int tickDelay;
-    private int spawnDelay;
-    private int spawnChance;
+    // Folia - region threading
 
     public WanderingTraderSpawner(ServerLevelData properties) {
         this.serverLevelData = properties;
         // Paper start - Add Wandering Trader spawn rate config options
-        this.tickDelay = Integer.MIN_VALUE;
+        //this.tickDelay = Integer.MIN_VALUE; // Folia - region threading - moved to regionisedworlddata
         //this.spawnDelay = properties.getWanderingTraderSpawnDelay(); // Paper - This value is read from the world file only for the first spawn, after which vanilla uses a hardcoded value
         //this.spawnChance = properties.getWanderingTraderSpawnChance(); // Paper - This value is read from the world file only for the first spawn, after which vanilla uses a hardcoded value
         //if (this.spawnDelay == 0 && this.spawnChance == 0) {
@@ -56,36 +54,37 @@ public class WanderingTraderSpawner implements CustomSpawner {
 
     @Override
     public int tick(ServerLevel world, boolean spawnMonsters, boolean spawnAnimals) {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
         // Paper start - Add Wandering Trader spawn rate config options
-        if (this.tickDelay == Integer.MIN_VALUE) {
-            this.tickDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnMinuteLength;
-            this.spawnDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnDayLength;
-            this.spawnChance = world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMin;
+        if (worldData.wanderingTraderTickDelay == Integer.MIN_VALUE) { // Folia - region threading
+            worldData.wanderingTraderTickDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnMinuteLength; // Folia - region threading
+            worldData.wanderingTraderSpawnDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnDayLength; // Folia - region threading
+            worldData.wanderingTraderSpawnChance = world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMin; // Folia - region threading
         }
         if (!world.getGameRules().getBoolean(GameRules.RULE_DO_TRADER_SPAWNING)) {
             return 0;
-        } else if (this.tickDelay - 1 > 0) {
-            this.tickDelay = this.tickDelay - 1;
+        } else if (worldData.wanderingTraderTickDelay - 1 > 0) { // Folia - region threading
+            worldData.wanderingTraderTickDelay = worldData.wanderingTraderTickDelay - 1; // Folia - region threading
             return 0;
         } else {
-            this.tickDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnMinuteLength;
-            this.spawnDelay = this.spawnDelay - world.paperConfig().entities.spawning.wanderingTrader.spawnMinuteLength;
+            worldData.wanderingTraderTickDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnMinuteLength; // Folia - region threading
+            worldData.wanderingTraderSpawnDelay = worldData.wanderingTraderSpawnDelay - world.paperConfig().entities.spawning.wanderingTrader.spawnMinuteLength; // Folia - region threading
             //this.serverLevelData.setWanderingTraderSpawnDelay(this.spawnDelay); // Paper - We don't need to save this value to disk if it gets set back to a hardcoded value anyways
-            if (this.spawnDelay > 0) {
+            if (worldData.wanderingTraderSpawnDelay > 0) { // Folia - region threading
                 return 0;
             } else {
-                this.spawnDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnDayLength;
+                worldData.wanderingTraderSpawnDelay = world.paperConfig().entities.spawning.wanderingTrader.spawnDayLength; // Folia - region threading
                 if (!world.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING)) {
                     return 0;
                 } else {
-                    int i = this.spawnChance;
+                    int i = worldData.wanderingTraderSpawnChance; // Folia - region threading
 
                     // this.serverLevelData.setWanderingTraderSpawnChance(this.spawnChance); // Paper - We don't need to save this value to disk if it gets set back to a hardcoded value anyways
-                    this.spawnChance = Mth.clamp(i + world.paperConfig().entities.spawning.wanderingTrader.spawnChanceFailureIncrement, world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMin, world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMax);
+                    worldData.wanderingTraderSpawnChance = Mth.clamp(i + world.paperConfig().entities.spawning.wanderingTrader.spawnChanceFailureIncrement, world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMin, world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMax); // Folia - region threading
                     if (this.random.nextInt(100) > i) {
                         return 0;
                     } else if (this.spawn(world)) {
-                        this.spawnChance = world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMin;
+                        worldData.wanderingTraderSpawnChance = world.paperConfig().entities.spawning.wanderingTrader.spawnChanceMin; // Folia - region threading
                         // Paper end - Add Wandering Trader spawn rate config options
                         return 1;
                     } else {
@@ -97,7 +96,7 @@ public class WanderingTraderSpawner implements CustomSpawner {
     }
 
     private boolean spawn(ServerLevel world) {
-        ServerPlayer entityplayer = world.getRandomPlayer();
+        ServerPlayer entityplayer = world.getRandomLocalPlayer(); // Folia - region threading
 
         if (entityplayer == null) {
             return true;
@@ -127,7 +126,7 @@ public class WanderingTraderSpawner implements CustomSpawner {
                         this.tryToSpawnLlamaFor(world, entityvillagertrader, 4);
                     }
 
-                    this.serverLevelData.setWanderingTraderId(entityvillagertrader.getUUID());
+                    //this.serverLevelData.setWanderingTraderId(entityvillagertrader.getUUID()); // Folia - region threading - doesn't appear to be used anywhere, so avoid the race condition here...
                     // entityvillagertrader.setDespawnDelay(48000); // CraftBukkit - moved to EntityVillagerTrader constructor. This lets the value be modified by plugins on CreatureSpawnEvent
                     entityvillagertrader.setWanderTarget(blockposition1);
                     entityvillagertrader.restrictTo(blockposition1, 16);
diff --git a/src/main/java/net/minecraft/world/entity/player/Player.java b/src/main/java/net/minecraft/world/entity/player/Player.java
index 567704f61034363e48ef2a5b5566ebdc91682297..579eb5a81281ca36c145153d8c24a517242ffe18 100644
--- a/src/main/java/net/minecraft/world/entity/player/Player.java
+++ b/src/main/java/net/minecraft/world/entity/player/Player.java
@@ -1528,6 +1528,14 @@ public abstract class Player extends LivingEntity {
 
     }
 
+    // Folia start - region threading
+    @Override
+    protected void preRemove(RemovalReason reason) {
+        super.preRemove(reason);
+        this.fishing = null;
+    }
+    // Folia end - region threading
+
     public boolean isLocalPlayer() {
         return false;
     }
diff --git a/src/main/java/net/minecraft/world/entity/projectile/AbstractArrow.java b/src/main/java/net/minecraft/world/entity/projectile/AbstractArrow.java
index e8faca6e443239968f0111519f9e5cd018ed3297..88aa1a41be9f596e07af3632def749aff9ea3363 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/AbstractArrow.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/AbstractArrow.java
@@ -157,6 +157,11 @@ public abstract class AbstractArrow extends Projectile {
     @Override
     public void tick() {
         super.tick();
+        // Folia start - region threading - make sure entities do not move into regions they do not own
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)this.level(), this.position(), this.getDeltaMovement(), 1)) {
+            return;
+        }
+        // Folia end - region threading - make sure entities do not move into regions they do not own
         boolean flag = this.isNoPhysics();
         Vec3 vec3d = this.getDeltaMovement();
 
diff --git a/src/main/java/net/minecraft/world/entity/projectile/AbstractHurtingProjectile.java b/src/main/java/net/minecraft/world/entity/projectile/AbstractHurtingProjectile.java
index 20ce474b72894a8bb3fc21018b9d79bbdc8bb14b..cd150b14afe46dcc5d96eb11106bf2bb4744c944 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/AbstractHurtingProjectile.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/AbstractHurtingProjectile.java
@@ -91,6 +91,11 @@ public abstract class AbstractHurtingProjectile extends Projectile {
             this.discard(EntityRemoveEvent.Cause.DESPAWN); // CraftBukkit - add Bukkit remove cause
         } else {
             super.tick();
+            // Folia start - region threading - make sure entities do not move into regions they do not own
+            if (!io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)this.level(), this.position(), this.getDeltaMovement(), 1)) {
+                return;
+            }
+            // Folia end - region threading - make sure entities do not move into regions they do not own
             if (this.shouldBurn()) {
                 this.setSecondsOnFire(1);
             }
diff --git a/src/main/java/net/minecraft/world/entity/projectile/FireworkRocketEntity.java b/src/main/java/net/minecraft/world/entity/projectile/FireworkRocketEntity.java
index 813c4a52c8ddd70e252125ebfd3654346c71f13c..2deddd55d6571bbab50ff8cdc6b705df9199f287 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/FireworkRocketEntity.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/FireworkRocketEntity.java
@@ -131,6 +131,11 @@ public class FireworkRocketEntity extends Projectile implements ItemSupplier {
 
                 });
             }
+            // Folia start - region threading
+            if (this.attachedToEntity != null && !io.papermc.paper.util.TickThread.isTickThreadFor(this.attachedToEntity)) {
+                this.attachedToEntity = null;
+            }
+            // Folia end - region threading
 
             if (this.attachedToEntity != null) {
                 if (this.attachedToEntity.isFallFlying()) {
diff --git a/src/main/java/net/minecraft/world/entity/projectile/FishingHook.java b/src/main/java/net/minecraft/world/entity/projectile/FishingHook.java
index 91497f5e6c07fcf1b05eca6846c51e1a15ed3bc0..16f847a21b0c636e8af332b999df4469b19cc943 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/FishingHook.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/FishingHook.java
@@ -105,7 +105,7 @@ public class FishingHook extends Projectile {
 
     public FishingHook(net.minecraft.world.entity.player.Player thrower, Level world, int luckOfTheSeaLevel, int lureLevel) {
         this(EntityType.FISHING_BOBBER, world, luckOfTheSeaLevel, lureLevel);
-        this.setOwner(thrower);
+        //this.setOwner(thrower); // Folia - region threading - move this down after position so that thread-checks do not fail
         float f = thrower.getXRot();
         float f1 = thrower.getYRot();
         float f2 = Mth.cos(-f1 * 0.017453292F - 3.1415927F);
@@ -117,6 +117,7 @@ public class FishingHook extends Projectile {
         double d2 = thrower.getZ() - (double) f2 * 0.3D;
 
         this.moveTo(d0, d1, d2, f1, f);
+        this.setOwner(thrower); // Folia - region threading - move this down after position so that thread-checks do not fail
         Vec3 vec3d = new Vec3((double) (-f3), (double) Mth.clamp(-(f5 / f4), -5.0F, 5.0F), (double) (-f2));
         double d3 = vec3d.length();
 
@@ -267,6 +268,11 @@ public class FishingHook extends Projectile {
     }
 
     private boolean shouldStopFishing(net.minecraft.world.entity.player.Player player) {
+        // Folia start - region threading
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(player)) {
+            return true;
+        }
+        // Folia end - region threading
         ItemStack itemstack = player.getMainHandItem();
         ItemStack itemstack1 = player.getOffhandItem();
         boolean flag = itemstack.is(Items.FISHING_ROD);
@@ -613,10 +619,18 @@ public class FishingHook extends Projectile {
     @Override
     public void remove(Entity.RemovalReason entity_removalreason, EntityRemoveEvent.Cause cause) {
         // CraftBukkit end
-        this.updateOwnerInfo((FishingHook) null);
+        // Folia - region threading - move into preRemove
         super.remove(entity_removalreason, cause); // CraftBukkit - add Bukkit remove cause
     }
 
+    // Folia start - region threading
+    @Override
+    protected void preRemove(RemovalReason reason) {
+        super.preRemove(reason);
+        this.updateOwnerInfo((FishingHook) null);
+    }
+    // Folia end - region threading
+
     @Override
     public void onClientRemoval() {
         this.updateOwnerInfo((FishingHook) null);
diff --git a/src/main/java/net/minecraft/world/entity/projectile/LlamaSpit.java b/src/main/java/net/minecraft/world/entity/projectile/LlamaSpit.java
index 8f5376543cca9cbfb2a014f67ec373d984b0df64..85a0f7b30db57a68133b38f42c17ac6e585fd629 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/LlamaSpit.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/LlamaSpit.java
@@ -32,6 +32,11 @@ public class LlamaSpit extends Projectile {
     @Override
     public void tick() {
         super.tick();
+        // Folia start - region threading - make sure entities do not move into regions they do not own
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)this.level(), this.position(), this.getDeltaMovement(), 1)) {
+            return;
+        }
+        // Folia end - region threading - make sure entities do not move into regions they do not own
         Vec3 vec3d = this.getDeltaMovement();
         HitResult movingobjectposition = ProjectileUtil.getHitResultOnMoveVector(this, this::canHitEntity);
 
diff --git a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
index 156809090f1f83ad68e7e2477a3cfddac5757a8e..10d7c64fb3a9bafdcdae99f8dc87017722341337 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
@@ -70,9 +70,20 @@ public abstract class Projectile extends Entity implements TraceableEntity {
     }
     // Paper end - Refresh ProjectileSource for projectiles
 
+    // Folia start - region threading
+    // In general, this is an entire mess. At the time of writing, there are fifty usages of getOwner.
+    // Usage of this function is to avoid concurrency issues, even if it sacrifices behavior.
     @Nullable
     @Override
     public Entity getOwner() {
+        Entity ret = this.getOwnerRaw();
+        return io.papermc.paper.util.TickThread.isTickThreadFor(ret) ? ret : null;
+    }
+    // Folia end - region threading
+
+    @Nullable
+    public Entity getOwnerRaw() { // Folia - region threading
+        io.papermc.paper.util.TickThread.ensureTickThread(this, "Cannot update owner state asynchronously"); // Folia - region threading
         if (this.cachedOwner != null && !this.cachedOwner.isRemoved()) {
             this.refreshProjectileSource(false); // Paper - Refresh ProjectileSource for projectiles
             return this.cachedOwner;
@@ -304,7 +315,7 @@ public abstract class Projectile extends Entity implements TraceableEntity {
     public boolean mayInteract(Level world, BlockPos pos) {
         Entity entity = this.getOwner();
 
-        return entity instanceof Player ? entity.mayInteract(world, pos) : entity == null || world.getGameRules().getBoolean(GameRules.RULE_MOBGRIEFING);
+        return entity instanceof Player && io.papermc.paper.util.TickThread.isTickThreadFor(entity) ? entity.mayInteract(world, pos) : entity == null || world.getGameRules().getBoolean(GameRules.RULE_MOBGRIEFING); // Folia - region threading
     }
 
     public boolean mayBreak(Level world) {
diff --git a/src/main/java/net/minecraft/world/entity/projectile/SmallFireball.java b/src/main/java/net/minecraft/world/entity/projectile/SmallFireball.java
index 6724fe4470aeea338eb4cfd10a7e61fbcac1e5b7..b6797d84356425945037d32b55c0d08c4699c8bf 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/SmallFireball.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/SmallFireball.java
@@ -26,7 +26,7 @@ public class SmallFireball extends Fireball {
     public SmallFireball(Level world, LivingEntity owner, double velocityX, double velocityY, double velocityZ) {
         super(EntityType.SMALL_FIREBALL, owner, velocityX, velocityY, velocityZ, world);
         // CraftBukkit start
-        if (this.getOwner() != null && this.getOwner() instanceof Mob) {
+        if (owner != null && owner instanceof Mob) { // Folia - region threading
             this.isIncendiary = this.level().getGameRules().getBoolean(GameRules.RULE_MOBGRIEFING);
         }
         // CraftBukkit end
diff --git a/src/main/java/net/minecraft/world/entity/projectile/ThrowableProjectile.java b/src/main/java/net/minecraft/world/entity/projectile/ThrowableProjectile.java
index ab777952bda1651796ed41e8a7fc6621f27db9aa..6b9365eba3339578ee2984605240b74db2b8a6c0 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/ThrowableProjectile.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/ThrowableProjectile.java
@@ -44,6 +44,11 @@ public abstract class ThrowableProjectile extends Projectile {
     @Override
     public void tick() {
         super.tick();
+        // Folia start - region threading - make sure entities do not move into regions they do not own
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)this.level(), this.position(), this.getDeltaMovement(), 1)) {
+            return;
+        }
+        // Folia end - region threading - make sure entities do not move into regions they do not own
         HitResult movingobjectposition = ProjectileUtil.getHitResultOnMoveVector(this, this::canHitEntity);
         boolean flag = false;
 
diff --git a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
index 1fb1e729d6879568d8b4943071fa940325b2e5b0..0c4b158d574ad0e9e257532ac3b9a3a34497216f 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
@@ -46,6 +46,78 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
         entityHitResult.getEntity().hurt(this.damageSources().thrown(this, this.getOwner()), 0.0F);
     }
 
+    // Folia start - region threading
+    private static void attemptTeleport(Entity source, ServerLevel checkWorld, net.minecraft.world.phys.Vec3 to) {
+        // ignore retired callback, in those cases we do not want to teleport
+        source.getBukkitEntity().taskScheduler.schedule(
+            (Entity entity) -> {
+                // source is now an invalid reference, do not use it, use the entity parameter
+                net.minecraft.world.phys.Vec3 endermitePos = entity.position();
+
+                if (entity.level() != checkWorld) {
+                    // cannot teleport cross-world
+                    return;
+                }
+                if (entity.isVehicle()) {
+                    // cannot teleport vehicles
+                    return;
+                }
+                // dismount from any vehicles, so we can teleport and to prevent desync
+                if (entity.isPassenger()) {
+                    entity.stopRiding();
+                }
+
+                // reset fall damage so that if the entity was falling they do not instantly die
+                entity.resetFallDistance();
+
+                entity.teleportAsync(
+                    checkWorld, to, null, null, null,
+                    PlayerTeleportEvent.TeleportCause.ENDER_PEARL,
+                    // chunk could have been unloaded
+                    Entity.TELEPORT_FLAG_LOAD_CHUNK,
+                    (Entity teleported) -> {
+                        // entity is now an invalid reference, do not use it, instead use teleported
+                        if (teleported instanceof ServerPlayer player) {
+                            // connection teleport is already done
+                            ServerLevel world = player.serverLevel();
+
+                            // endermite spawn chance
+                            if (world.random.nextFloat() < 0.05F && world.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING)) {
+                                Endermite entityendermite = (Endermite) EntityType.ENDERMITE.create(world);
+
+                                if (entityendermite != null) {
+                                    float yRot = teleported.getYRot();
+                                    float xRot = teleported.getXRot();
+                                    Runnable spawn = () -> {
+                                        entityendermite.moveTo(endermitePos.x, endermitePos.y, endermitePos.z, yRot, xRot);
+                                        world.addFreshEntity(entityendermite, CreatureSpawnEvent.SpawnReason.ENDER_PEARL);
+                                    };
+
+                                    if (io.papermc.paper.util.TickThread.isTickThreadFor(world, endermitePos, net.minecraft.world.phys.Vec3.ZERO, 1)) {
+                                        spawn.run();
+                                    } else {
+                                        io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                                            world,
+                                            io.papermc.paper.util.CoordinateUtils.getChunkCoordinate(endermitePos.x),
+                                            io.papermc.paper.util.CoordinateUtils.getChunkCoordinate(endermitePos.z),
+                                            spawn
+                                        );
+                                    }
+                                }
+                            }
+
+                            // damage player
+                            player.hurt(player.damageSources().fall(), 5.0F);
+                        }
+                    }
+                );
+            },
+            null,
+            1L
+        );
+    }
+    // Folia end - region threading
+
     @Override
     protected void onHit(HitResult hitResult) {
         super.onHit(hitResult);
@@ -55,6 +127,20 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
         }
 
         if (!this.level().isClientSide && !this.isRemoved()) {
+            // Folia start - region threading
+            if (true) {
+                // we can't fire events, because we do not actually know where the other entity is located
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(this)) {
+                    throw new IllegalStateException("Must be on tick thread for ticking entity: " + this);
+                }
+                Entity entity = this.getOwnerRaw();
+                if (entity != null) {
+                    attemptTeleport(entity, (ServerLevel)this.level(), this.position());
+                }
+                this.discard(EntityRemoveEvent.Cause.HIT);
+                return;
+            }
+            // Folia end - region threading
             Entity entity = this.getOwner();
 
             if (entity instanceof ServerPlayer) {
@@ -113,6 +199,14 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
 
     }
 
+    // Folia start - region threading
+    @Override
+    public void preChangeDimension() {
+        super.preChangeDimension();
+        // Don't change the owner here, since the tick logic will consider it anyways.
+    }
+    // Folia end - region threading
+
     @Nullable
     @Override
     public Entity changeDimension(ServerLevel destination) {
diff --git a/src/main/java/net/minecraft/world/entity/raid/Raid.java b/src/main/java/net/minecraft/world/entity/raid/Raid.java
index bf2c23fad919820512ce031cf28a000b249b2876..2905dab1f9b3dd846261c5b0777d073927882825 100644
--- a/src/main/java/net/minecraft/world/entity/raid/Raid.java
+++ b/src/main/java/net/minecraft/world/entity/raid/Raid.java
@@ -112,6 +112,13 @@ public class Raid {
     public final org.bukkit.craftbukkit.persistence.CraftPersistentDataContainer persistentDataContainer = new org.bukkit.craftbukkit.persistence.CraftPersistentDataContainer(PDC_TYPE_REGISTRY);
     // Paper end
 
+    // Folia start - make raids thread-safe
+    public boolean ownsRaid() {
+        BlockPos center = this.getCenter();
+        return center != null && io.papermc.paper.util.TickThread.isTickThreadFor(this.level, center.getX() >> 4, center.getZ() >> 4, 8);
+    }
+    // Folia end - make raids thread-safe
+
     public Raid(int id, ServerLevel world, BlockPos pos) {
         this.raidEvent = new ServerBossEvent(Raid.RAID_NAME_COMPONENT, BossEvent.BossBarColor.RED, BossEvent.BossBarOverlay.NOTCHED_10);
         this.random = RandomSource.create();
@@ -225,7 +232,7 @@ public class Raid {
         return (entityplayer) -> {
             BlockPos blockposition = entityplayer.blockPosition();
 
-            return entityplayer.isAlive() && this.level.getRaidAt(blockposition) == this;
+            return io.papermc.paper.util.TickThread.isTickThreadFor(entityplayer) && entityplayer.isAlive() && this.level.getRaidAt(blockposition) == this; // Folia - make raids thread-safe
         };
     }
 
@@ -541,7 +548,7 @@ public class Raid {
         boolean flag = true;
         Collection<ServerPlayer> collection = this.raidEvent.getPlayers();
         long i = this.random.nextLong();
-        Iterator iterator = this.level.players().iterator();
+        Iterator iterator = this.level.getLocalPlayers().iterator(); // Folia - region threading
 
         while (iterator.hasNext()) {
             ServerPlayer entityplayer = (ServerPlayer) iterator.next();
diff --git a/src/main/java/net/minecraft/world/entity/raid/Raider.java b/src/main/java/net/minecraft/world/entity/raid/Raider.java
index 93bbf7556f9599e9dd90761085a57d78bd521867..15e1ce9d50f176e475295f7d5e8d039f49e84ad8 100644
--- a/src/main/java/net/minecraft/world/entity/raid/Raider.java
+++ b/src/main/java/net/minecraft/world/entity/raid/Raider.java
@@ -94,7 +94,7 @@ public abstract class Raider extends PatrollingMonster {
 
             if (this.canJoinRaid()) {
                 if (raid == null) {
-                    if (this.level().getGameTime() % 20L == 0L) {
+                    if (this.level().getRedstoneGameTime() % 20L == 0L) { // Folia - region threading
                         Raid raid1 = ((ServerLevel) this.level()).getRaidAt(this.blockPosition());
 
                         if (raid1 != null && Raids.canJoinRaid(this, raid1)) {
diff --git a/src/main/java/net/minecraft/world/entity/raid/Raids.java b/src/main/java/net/minecraft/world/entity/raid/Raids.java
index 31831811ce16265e9828fa34d9e67d8ac195d723..287024eaee26390a469162d63045a7cb1bfc20cf 100644
--- a/src/main/java/net/minecraft/world/entity/raid/Raids.java
+++ b/src/main/java/net/minecraft/world/entity/raid/Raids.java
@@ -29,9 +29,9 @@ import net.minecraft.world.phys.Vec3;
 public class Raids extends SavedData {
 
     private static final String RAID_FILE_ID = "raids";
-    public final Map<Integer, Raid> raidMap = Maps.newHashMap();
+    public final Map<Integer, Raid> raidMap = new java.util.concurrent.ConcurrentHashMap<>(); // Folia - make raids thread-safe
     private final ServerLevel level;
-    private int nextAvailableID;
+    private final java.util.concurrent.atomic.AtomicInteger nextAvailableID = new java.util.concurrent.atomic.AtomicInteger(); // Folia - make raids thread-safe
     private int tick;
 
     public static SavedData.Factory<Raids> factory(ServerLevel world) {
@@ -44,7 +44,7 @@ public class Raids extends SavedData {
 
     public Raids(ServerLevel world) {
         this.level = world;
-        this.nextAvailableID = 1;
+        this.nextAvailableID.set(1); // Folia - make raids thread-safe
         this.setDirty();
     }
 
@@ -52,12 +52,26 @@ public class Raids extends SavedData {
         return (Raid) this.raidMap.get(id);
     }
 
-    public void tick() {
+    // Folia start - make raids thread-safe
+    public void globalTick() {
         ++this.tick;
+        if (this.tick % 200 == 0) {
+            this.setDirty();
+        }
+    }
+    // Folia end - make raids thread-safe
+
+    public void tick() {
+        // Folia - make raids thread-safe - move to globalTick()
         Iterator iterator = this.raidMap.values().iterator();
 
         while (iterator.hasNext()) {
             Raid raid = (Raid) iterator.next();
+            // Folia start - make raids thread-safe
+            if (!raid.ownsRaid()) {
+                continue;
+            }
+            // Folia end - make raids thread-safe
 
             if (this.level.getGameRules().getBoolean(GameRules.RULE_DISABLE_RAIDS)) {
                 raid.stop();
@@ -71,14 +85,17 @@ public class Raids extends SavedData {
             }
         }
 
-        if (this.tick % 200 == 0) {
-            this.setDirty();
-        }
+        // Folia - make raids thread-safe - move to globalTick()
 
         DebugPackets.sendRaids(this.level, this.raidMap.values());
     }
 
     public static boolean canJoinRaid(Raider raider, Raid raid) {
+        // Folia start - make raids thread-safe
+        if (!raid.ownsRaid()) {
+            return false;
+        }
+        // Folia end - make raids thread-safe
         return raider != null && raid != null && raid.getLevel() != null ? raider.isAlive() && raider.canJoinRaid() && raider.getNoActionTime() <= 2400 && raider.level().dimensionType() == raid.getLevel().dimensionType() : false;
     }
 
@@ -91,7 +108,7 @@ public class Raids extends SavedData {
         } else {
             DimensionType dimensionmanager = player.level().dimensionType();
 
-            if (!dimensionmanager.hasRaids()) {
+            if (!dimensionmanager.hasRaids() || !io.papermc.paper.util.TickThread.isTickThreadFor(this.level, player.chunkPosition().x, player.chunkPosition().z, 8)) { // Folia - region threading
                 return null;
             } else {
                 BlockPos blockposition = player.blockPosition();
@@ -171,7 +188,7 @@ public class Raids extends SavedData {
     public static Raids load(ServerLevel world, CompoundTag nbt) {
         Raids persistentraid = new Raids(world);
 
-        persistentraid.nextAvailableID = nbt.getInt("NextAvailableID");
+        persistentraid.nextAvailableID.set(nbt.getInt("NextAvailableID")); // Folia - make raids thread-safe
         persistentraid.tick = nbt.getInt("Tick");
         ListTag nbttaglist = nbt.getList("Raids", 10);
 
@@ -187,7 +204,7 @@ public class Raids extends SavedData {
 
     @Override
     public CompoundTag save(CompoundTag nbt) {
-        nbt.putInt("NextAvailableID", this.nextAvailableID);
+        nbt.putInt("NextAvailableID", this.nextAvailableID.get()); // Folia - make raids thread-safe
         nbt.putInt("Tick", this.tick);
         ListTag nbttaglist = new ListTag();
         Iterator iterator = this.raidMap.values().iterator();
@@ -209,7 +226,7 @@ public class Raids extends SavedData {
     }
 
     private int getUniqueId() {
-        return ++this.nextAvailableID;
+        return this.nextAvailableID.incrementAndGet(); // Folia - make raids thread-safe
     }
 
     @Nullable
@@ -220,6 +237,11 @@ public class Raids extends SavedData {
 
         while (iterator.hasNext()) {
             Raid raid1 = (Raid) iterator.next();
+            // Folia start - make raids thread-safe
+            if (!raid1.ownsRaid()) {
+                continue;
+            }
+            // Folia end - make raids thread-safe
             double d1 = raid1.getCenter().distSqr(pos);
 
             if (raid1.isActive() && d1 < d0) {
diff --git a/src/main/java/net/minecraft/world/entity/vehicle/MinecartCommandBlock.java b/src/main/java/net/minecraft/world/entity/vehicle/MinecartCommandBlock.java
index 88b00556322f078b8a9d28fb7c759bb8c84bfcf0..9badca2723f43e4caddb741252caeaf5f57ba9d6 100644
--- a/src/main/java/net/minecraft/world/entity/vehicle/MinecartCommandBlock.java
+++ b/src/main/java/net/minecraft/world/entity/vehicle/MinecartCommandBlock.java
@@ -150,5 +150,11 @@ public class MinecartCommandBlock extends AbstractMinecart {
             return (org.bukkit.craftbukkit.entity.CraftMinecartCommand) MinecartCommandBlock.this.getBukkitEntity();
         }
         // CraftBukkit end
+        // Folia start
+        @Override
+        public void threadCheck() {
+            io.papermc.paper.util.TickThread.ensureTickThread(MinecartCommandBlock.this, "Asynchronous sendSystemMessage to a command block");
+        }
+        // Folia end
     }
 }
diff --git a/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java b/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java
index 761142374f793a1cd4228936b21a68d7a0458894..b04f06aeb62cdc0f498dc97049bf27862da51b1d 100644
--- a/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java
+++ b/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java
@@ -127,7 +127,7 @@ public class MinecartHopper extends AbstractMinecartContainer implements Hopper
 
     // Paper start
     public void immunize() {
-        this.activatedImmunityTick = Math.max(this.activatedImmunityTick, net.minecraft.server.MinecraftServer.currentTick + 20);
+        this.activatedImmunityTick = Math.max(this.activatedImmunityTick, io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + 20);
     }
     // Paper end
 
diff --git a/src/main/java/net/minecraft/world/item/ArmorItem.java b/src/main/java/net/minecraft/world/item/ArmorItem.java
index 6b81be03f87967124b046708557e05d519aa79e4..2220ac02eec17c0791e5b4ce8f5e085333471127 100644
--- a/src/main/java/net/minecraft/world/item/ArmorItem.java
+++ b/src/main/java/net/minecraft/world/item/ArmorItem.java
@@ -75,7 +75,7 @@ public class ArmorItem extends Item implements Equipable {
             CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
             BlockDispenseArmorEvent event = new BlockDispenseArmorEvent(block, craftItem.clone(), (org.bukkit.craftbukkit.entity.CraftLivingEntity) entityliving.getBukkitEntity());
-            if (!DispenserBlock.eventFired) {
+            if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                 world.getCraftServer().getPluginManager().callEvent(event);
             }
 
diff --git a/src/main/java/net/minecraft/world/item/ItemStack.java b/src/main/java/net/minecraft/world/item/ItemStack.java
index 1ad126d992d95062a3db08374db7a927f23a0cac..43d8f91cdbc4e197f2811fb406a7dae8a8ebfdc1 100644
--- a/src/main/java/net/minecraft/world/item/ItemStack.java
+++ b/src/main/java/net/minecraft/world/item/ItemStack.java
@@ -379,31 +379,32 @@ public final class ItemStack {
             CompoundTag oldData = this.getTagClone();
             int oldCount = this.getCount();
             ServerLevel world = (ServerLevel) context.getLevel();
+            io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
 
             if (!(item instanceof BucketItem/* || item instanceof SolidBucketItem*/)) { // if not bucket // Paper - Fix cancelled powdered snow bucket placement
-                world.captureBlockStates = true;
+                worldData.captureBlockStates = true; // Folia - region threading
                 // special case bonemeal
                 if (item == Items.BONE_MEAL) {
-                    world.captureTreeGeneration = true;
+                    worldData.captureTreeGeneration = true; // Folia - region threading
                 }
             }
             InteractionResult enuminteractionresult;
             try {
                 enuminteractionresult = item.useOn(context);
             } finally {
-                world.captureBlockStates = false;
+                worldData.captureBlockStates = false; // Folia - region threading
             }
             CompoundTag newData = this.getTagClone();
             int newCount = this.getCount();
             this.setCount(oldCount);
             this.setTagClone(oldData);
-            if (enuminteractionresult.consumesAction() && world.captureTreeGeneration && world.capturedBlockStates.size() > 0) {
-                world.captureTreeGeneration = false;
+            if (enuminteractionresult.consumesAction() && worldData.captureTreeGeneration && worldData.capturedBlockStates.size() > 0) { // Folia - region threading
+                world.getCurrentWorldData().captureTreeGeneration = false; // Folia - region threading
                 Location location = CraftLocation.toBukkit(blockposition, world.getWorld());
-                TreeType treeType = SaplingBlock.treeType;
-                SaplingBlock.treeType = null;
-                List<CraftBlockState> blocks = new java.util.ArrayList<>(world.capturedBlockStates.values());
-                world.capturedBlockStates.clear();
+                TreeType treeType = SaplingBlock.treeTypeRT.get(); // Folia - region threading
+                SaplingBlock.treeTypeRT.set(null); // Folia - region threading
+                List<CraftBlockState> blocks = new java.util.ArrayList<>(worldData.capturedBlockStates.values()); // Folia - region threading
+                worldData.capturedBlockStates.clear(); // Folia - region threading
                 StructureGrowEvent structureEvent = null;
                 if (treeType != null) {
                     boolean isBonemeal = this.getItem() == Items.BONE_MEAL;
@@ -429,16 +430,16 @@ public final class ItemStack {
                     entityhuman.awardStat(Stats.ITEM_USED.get(item)); // SPIGOT-7236 - award stat
                 }
 
-                SignItem.openSign = null; // SPIGOT-6758 - Reset on early return
+                SignItem.openSign.set(null); // SPIGOT-6758 - Reset on early return // Folia - region threading
                 return enuminteractionresult;
             }
-            world.captureTreeGeneration = false;
+            worldData.captureTreeGeneration = false; // Folia - region threading
 
             if (entityhuman != null && enuminteractionresult.shouldAwardStats()) {
                 InteractionHand enumhand = context.getHand();
                 org.bukkit.event.block.BlockPlaceEvent placeEvent = null;
-                List<BlockState> blocks = new java.util.ArrayList<>(world.capturedBlockStates.values());
-                world.capturedBlockStates.clear();
+                List<BlockState> blocks = new java.util.ArrayList<>(worldData.capturedBlockStates.values()); // Folia - region threading
+                worldData.capturedBlockStates.clear(); // Folia - region threading
                 if (blocks.size() > 1) {
                     placeEvent = org.bukkit.craftbukkit.event.CraftEventFactory.callBlockMultiPlaceEvent(world, entityhuman, enumhand, blocks, blockposition.getX(), blockposition.getY(), blockposition.getZ());
                 } else if (blocks.size() == 1 && item != Items.POWDER_SNOW_BUCKET) { // Paper - Fix cancelled powdered snow bucket placement
@@ -449,13 +450,13 @@ public final class ItemStack {
                     enuminteractionresult = InteractionResult.FAIL; // cancel placement
                     // PAIL: Remove this when MC-99075 fixed
                     placeEvent.getPlayer().updateInventory();
-                    world.capturedTileEntities.clear(); // Paper - Allow chests to be placed with NBT data; clear out block entities as chests and such will pop loot
+                    worldData.capturedTileEntities.clear(); // Paper - Allow chests to be placed with NBT data; clear out block entities as chests and such will pop loot // Folia - region threading
                     // revert back all captured blocks
-                    world.preventPoiUpdated = true; // CraftBukkit - SPIGOT-5710
+                    worldData.preventPoiUpdated = true; // CraftBukkit - SPIGOT-5710 // Folia - region threading
                     for (BlockState blockstate : blocks) {
                         blockstate.update(true, false);
                     }
-                    world.preventPoiUpdated = false;
+                    worldData.preventPoiUpdated = false; // Folia - region threading
 
                     // Brute force all possible updates
                     // Paper start - Don't resync blocks
@@ -464,7 +465,7 @@ public final class ItemStack {
                     //     ((ServerPlayer) entityhuman).connection.send(new ClientboundBlockUpdatePacket(world, placedPos.relative(dir)));
                     // }
                     // Paper end - Don't resync blocks
-                    SignItem.openSign = null; // SPIGOT-6758 - Reset on early return
+                    SignItem.openSign.set(null); // SPIGOT-6758 - Reset on early return // Folia - region threading
                 } else {
                     // Change the stack to its new contents if it hasn't been tampered with.
                     if (this.getCount() == oldCount && Objects.equals(this.tag, oldData)) {
@@ -472,7 +473,7 @@ public final class ItemStack {
                         this.setCount(newCount);
                     }
 
-                    for (Map.Entry<BlockPos, BlockEntity> e : world.capturedTileEntities.entrySet()) {
+                    for (Map.Entry<BlockPos, BlockEntity> e : worldData.capturedTileEntities.entrySet()) { // Folia - region threading
                         world.setBlockEntity(e.getValue());
                     }
 
@@ -523,15 +524,15 @@ public final class ItemStack {
                     }
 
                     // SPIGOT-4678
-                    if (this.item instanceof SignItem && SignItem.openSign != null) {
+                    if (this.item instanceof SignItem && SignItem.openSign.get() != null) { // Folia - region threading
                         try {
-                            if (world.getBlockEntity(SignItem.openSign) instanceof SignBlockEntity tileentitysign) {
-                                if (world.getBlockState(SignItem.openSign).getBlock() instanceof SignBlock blocksign) {
+                            if (world.getBlockEntity(SignItem.openSign.get()) instanceof SignBlockEntity tileentitysign) { // Folia - region threading
+                                if (world.getBlockState(SignItem.openSign.get()).getBlock() instanceof SignBlock blocksign) { // Folia - region threading
                                     blocksign.openTextEdit(entityhuman, tileentitysign, true, io.papermc.paper.event.player.PlayerOpenSignEvent.Cause.PLACE); // Paper - Add PlayerOpenSignEvent
                                 }
                             }
                         } finally {
-                            SignItem.openSign = null;
+                            SignItem.openSign.set(null); // Folia - region threading
                         }
                     }
 
@@ -559,8 +560,8 @@ public final class ItemStack {
                     entityhuman.awardStat(Stats.ITEM_USED.get(item));
                 }
             }
-            world.capturedTileEntities.clear();
-            world.capturedBlockStates.clear();
+            worldData.capturedTileEntities.clear(); // Folia - region threading
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             // CraftBukkit end
 
             return enuminteractionresult;
diff --git a/src/main/java/net/minecraft/world/item/MapItem.java b/src/main/java/net/minecraft/world/item/MapItem.java
index d8dd99ec8bf7444c5a3c426db3a9c13e334dc0ff..5204449e94eeadb9b0485a0b4ff876196f40051c 100644
--- a/src/main/java/net/minecraft/world/item/MapItem.java
+++ b/src/main/java/net/minecraft/world/item/MapItem.java
@@ -95,6 +95,7 @@ public class MapItem extends ComplexItem {
     }
 
     public void update(Level world, Entity entity, MapItemSavedData state) {
+        synchronized (state) { // Folia - make map data thread-safe
         if (world.dimension() == state.dimension && entity instanceof Player) {
             int i = 1 << state.scale;
             int j = state.centerX;
@@ -126,9 +127,9 @@ public class MapItem extends ComplexItem {
                             int j2 = (j / i + k1 - 64) * i;
                             int k2 = (k / i + l1 - 64) * i;
                             Multiset<MapColor> multiset = LinkedHashMultiset.create();
-                            LevelChunk chunk = world.getChunkIfLoaded(SectionPos.blockToSectionCoord(j2), SectionPos.blockToSectionCoord(k2)); // Paper - Maps shouldn't load chunks
+                            LevelChunk chunk = world.getChunkIfLoaded(SectionPos.blockToSectionCoord(j2), SectionPos.blockToSectionCoord(k2)); // Paper - Maps shouldn't load chunks // Folia - super important that it uses getChunkIfLoaded
 
-                            if (chunk != null && !chunk.isEmpty()) { // Paper - Maps shouldn't load chunks
+                            if (chunk != null && !chunk.isEmpty() && io.papermc.paper.util.TickThread.isTickThreadFor((ServerLevel)world, chunk.getPos())) { // Paper - Maps shouldn't load chunks // Folia - make sure chunk is owned
                                 int l2 = 0;
                                 double d1 = 0.0D;
                                 int i3;
@@ -219,6 +220,7 @@ public class MapItem extends ComplexItem {
             }
 
         }
+        } // Folia - make map data thread-safe
     }
 
     private BlockState getCorrectStateForFluidBlock(Level world, BlockState state, BlockPos pos) {
@@ -235,6 +237,7 @@ public class MapItem extends ComplexItem {
         MapItemSavedData worldmap = MapItem.getSavedData(map, world);
 
         if (worldmap != null) {
+            synchronized (worldmap) { // Folia - make map data thread-safe
             if (world.dimension() == worldmap.dimension) {
                 int i = 1 << worldmap.scale;
                 int j = worldmap.centerX;
@@ -309,6 +312,7 @@ public class MapItem extends ComplexItem {
                 }
 
             }
+            } // Folia - make map data thread-safe
         }
     }
 
@@ -318,6 +322,7 @@ public class MapItem extends ComplexItem {
             MapItemSavedData worldmap = MapItem.getSavedData(stack, world);
 
             if (worldmap != null) {
+                synchronized (worldmap) { // Folia - region threading
                 if (entity instanceof Player) {
                     Player entityhuman = (Player) entity;
 
@@ -327,6 +332,7 @@ public class MapItem extends ComplexItem {
                 if (!worldmap.locked && (selected || entity instanceof Player && ((Player) entity).getOffhandItem() == stack)) {
                     this.update(world, entity, worldmap);
                 }
+                } // Folia - region threading
 
             }
         }
diff --git a/src/main/java/net/minecraft/world/item/MinecartItem.java b/src/main/java/net/minecraft/world/item/MinecartItem.java
index 3aa73cd44aa8c86b78c35bc1788e4f83018c49ed..cfead7686da25d2cd9203256962170d7a2d77289 100644
--- a/src/main/java/net/minecraft/world/item/MinecartItem.java
+++ b/src/main/java/net/minecraft/world/item/MinecartItem.java
@@ -70,7 +70,7 @@ public class MinecartItem extends Item {
             CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
             BlockDispenseEvent event = new BlockDispenseEvent(block2, craftItem.clone(), new org.bukkit.util.Vector(d0, d1 + d3, d2));
-            if (!DispenserBlock.eventFired) {
+            if (!DispenserBlock.eventFired.get()) { // Folia - region threading
                 worldserver.getCraftServer().getPluginManager().callEvent(event);
             }
 
diff --git a/src/main/java/net/minecraft/world/item/SignItem.java b/src/main/java/net/minecraft/world/item/SignItem.java
index 21c25026da4117b2cb2c85576d2def945a97dbe2..e0b51cb4ef9e847dc9a2e66f2c87c94d6d93c6a3 100644
--- a/src/main/java/net/minecraft/world/item/SignItem.java
+++ b/src/main/java/net/minecraft/world/item/SignItem.java
@@ -13,7 +13,7 @@ import net.minecraft.world.level.block.state.BlockState;
 
 public class SignItem extends StandingAndWallBlockItem {
 
-    public static BlockPos openSign; // CraftBukkit
+    public static final ThreadLocal<BlockPos> openSign = new ThreadLocal<>(); // CraftBukkit // Folia - region threading
 
     public SignItem(Item.Properties settings, Block standingBlock, Block wallBlock) {
         super(standingBlock, wallBlock, settings, Direction.DOWN);
@@ -39,7 +39,7 @@ public class SignItem extends StandingAndWallBlockItem {
 
                     // CraftBukkit start - SPIGOT-4678
                     // blocksign.openTextEdit(entityhuman, tileentitysign, true);
-                    SignItem.openSign = pos;
+                    SignItem.openSign.set(pos); // Folia - region threading
                     // CraftBukkit end
                 }
             }
diff --git a/src/main/java/net/minecraft/world/level/BaseCommandBlock.java b/src/main/java/net/minecraft/world/level/BaseCommandBlock.java
index 524b0f1086c01888fe0b76e180c40915d16a1eb9..50b3025189938374886c7e2725dd3e4d54ac2160 100644
--- a/src/main/java/net/minecraft/world/level/BaseCommandBlock.java
+++ b/src/main/java/net/minecraft/world/level/BaseCommandBlock.java
@@ -20,7 +20,7 @@ import net.minecraft.world.phys.Vec3;
 
 public abstract class BaseCommandBlock implements CommandSource {
 
-    private static final SimpleDateFormat TIME_FORMAT = new SimpleDateFormat("HH:mm:ss");
+    private static final ThreadLocal<SimpleDateFormat> TIME_FORMAT = ThreadLocal.withInitial(() -> new SimpleDateFormat("HH:mm:ss")); // Folia - region threading - SDF is not thread-safe
     private static final Component DEFAULT_NAME = Component.literal("@");
     private long lastExecution = -1L;
     private boolean updateLastExecution = true;
@@ -111,6 +111,7 @@ public abstract class BaseCommandBlock implements CommandSource {
     }
 
     public boolean performCommand(Level world) {
+        if (true) return false; // Folia - region threading
         if (!world.isClientSide && world.getGameTime() != this.lastExecution) {
             if ("Searge".equalsIgnoreCase(this.command)) {
                 this.lastOutput = Component.literal("#itzlipofutzli");
@@ -169,11 +170,14 @@ public abstract class BaseCommandBlock implements CommandSource {
 
     }
 
+    public void threadCheck() {} // Folia
+
     @Override
     public void sendSystemMessage(Component message) {
         if (this.trackOutput) {
             org.spigotmc.AsyncCatcher.catchOp("sendSystemMessage to a command block"); // Paper - Don't broadcast messages to command blocks
-            SimpleDateFormat simpledateformat = BaseCommandBlock.TIME_FORMAT;
+            this.threadCheck(); // Folia
+            SimpleDateFormat simpledateformat = BaseCommandBlock.TIME_FORMAT.get(); // Folia - region threading - SDF is not thread-safe
             Date date = new Date();
 
             this.lastOutput = Component.literal("[" + simpledateformat.format(date) + "] ").append(message);
diff --git a/src/main/java/net/minecraft/world/level/EntityGetter.java b/src/main/java/net/minecraft/world/level/EntityGetter.java
index ea0aee88c7d901034427db201c1b2430f8a1d522..2a147a839e78b1d7bfb5eea86975402598aacf6c 100644
--- a/src/main/java/net/minecraft/world/level/EntityGetter.java
+++ b/src/main/java/net/minecraft/world/level/EntityGetter.java
@@ -39,6 +39,12 @@ public interface EntityGetter {
         return this.getEntities(EntityTypeTest.forClass(entityClass), box, predicate);
     }
 
+    // Folia start - region threading
+    default List<? extends Player> getLocalPlayers() {
+        return java.util.Collections.emptyList();
+    }
+    // Folia end - region threading
+
     List<? extends Player> players();
 
     default List<Entity> getEntities(@Nullable Entity except, AABB box) {
@@ -130,7 +136,7 @@ public interface EntityGetter {
         double d = -1.0;
         Player player = null;
 
-        for (Player player2 : this.players()) {
+        for (Player player2 : this.getLocalPlayers()) { // Folia - region threading
             if (targetPredicate == null || targetPredicate.test(player2)) {
                 double e = player2.distanceToSqr(x, y, z);
                 if ((maxDistance < 0.0 || e < maxDistance * maxDistance) && (d == -1.0 || e < d)) {
@@ -151,7 +157,7 @@ public interface EntityGetter {
     default List<org.bukkit.entity.HumanEntity> findNearbyBukkitPlayers(double x, double y, double z, double radius, @Nullable Predicate<Entity> predicate) {
         com.google.common.collect.ImmutableList.Builder<org.bukkit.entity.HumanEntity> builder = com.google.common.collect.ImmutableList.builder();
 
-        for (Player human : this.players()) {
+        for (Player human : this.getLocalPlayers()) { // Folia - region threading
             if (predicate == null || predicate.test(human)) {
                 double distanceSquared = human.distanceToSqr(x, y, z);
 
@@ -178,7 +184,7 @@ public interface EntityGetter {
 
     // Paper start - Affects Spawning API
     default boolean hasNearbyAlivePlayerThatAffectsSpawning(double x, double y, double z, double range) {
-        for (Player player : this.players()) {
+        for (Player player : this.getLocalPlayers()) { // Folia - region threading
             if (EntitySelector.PLAYER_AFFECTS_SPAWNING.test(player)) { // combines NO_SPECTATORS and LIVING_ENTITY_STILL_ALIVE with an "affects spawning" check
                 double distanceSqr = player.distanceToSqr(x, y, z);
                 if (range < 0.0D || distanceSqr < range * range) {
@@ -191,7 +197,7 @@ public interface EntityGetter {
     // Paper end - Affects Spawning API
 
     default boolean hasNearbyAlivePlayer(double x, double y, double z, double range) {
-        for (Player player : this.players()) {
+        for (Player player : this.getLocalPlayers()) { // Folia - region threading
             if (EntitySelector.NO_SPECTATORS.test(player) && EntitySelector.LIVING_ENTITY_STILL_ALIVE.test(player)) {
                 double d = player.distanceToSqr(x, y, z);
                 if (range < 0.0 || d < range * range) {
@@ -205,17 +211,17 @@ public interface EntityGetter {
 
     @Nullable
     default Player getNearestPlayer(TargetingConditions targetPredicate, LivingEntity entity) {
-        return this.getNearestEntity(this.players(), targetPredicate, entity, entity.getX(), entity.getY(), entity.getZ());
+        return this.getNearestEntity(this.getLocalPlayers(), targetPredicate, entity, entity.getX(), entity.getY(), entity.getZ()); // Folia - region threading
     }
 
     @Nullable
     default Player getNearestPlayer(TargetingConditions targetPredicate, LivingEntity entity, double x, double y, double z) {
-        return this.getNearestEntity(this.players(), targetPredicate, entity, x, y, z);
+        return this.getNearestEntity(this.getLocalPlayers(), targetPredicate, entity, x, y, z); // Folia - region threading
     }
 
     @Nullable
     default Player getNearestPlayer(TargetingConditions targetPredicate, double x, double y, double z) {
-        return this.getNearestEntity(this.players(), targetPredicate, null, x, y, z);
+        return this.getNearestEntity(this.getLocalPlayers(), targetPredicate, null, x, y, z); // Folia - region threading
     }
 
     @Nullable
@@ -252,7 +258,7 @@ public interface EntityGetter {
     default List<Player> getNearbyPlayers(TargetingConditions targetPredicate, LivingEntity entity, AABB box) {
         List<Player> list = Lists.newArrayList();
 
-        for (Player player : this.players()) {
+        for (Player player : this.getLocalPlayers()) { // Folia - region threading
             if (box.contains(player.getX(), player.getY(), player.getZ()) && targetPredicate.test(entity, player)) {
                 list.add(player);
             }
@@ -278,8 +284,7 @@ public interface EntityGetter {
 
     @Nullable
     default Player getPlayerByUUID(UUID uuid) {
-        for (int i = 0; i < this.players().size(); i++) {
-            Player player = this.players().get(i);
+        for (Player player : this.getLocalPlayers()) { // Folia - region threading
             if (uuid.equals(player.getUUID())) {
                 return player;
             }
diff --git a/src/main/java/net/minecraft/world/level/Explosion.java b/src/main/java/net/minecraft/world/level/Explosion.java
index 90a82bd7977ebe520bdcc2ab99e11452d5cf4a21..b937437d4446fbf80376399067fd04dc7f95e64a 100644
--- a/src/main/java/net/minecraft/world/level/Explosion.java
+++ b/src/main/java/net/minecraft/world/level/Explosion.java
@@ -870,17 +870,18 @@ public class Explosion {
         if (!this.level.paperConfig().environment.optimizeExplosions) {
             return this.getSeenFraction(vec3d, entity, blockCache, blockPos); // Paper - optimise explosions
         }
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.level.getCurrentWorldData(); // Folia - region threading
         CacheKey key = new CacheKey(this, entity.getBoundingBox());
-        Float blockDensity = this.level.explosionDensityCache.get(key);
+        Float blockDensity = worldData.explosionDensityCache.get(key); // Folia - region threading
         if (blockDensity == null) {
             blockDensity = this.getSeenFraction(vec3d, entity, blockCache, blockPos); // Paper - optimise explosions;
-            this.level.explosionDensityCache.put(key, blockDensity);
+            worldData.explosionDensityCache.put(key, blockDensity); // Folia - region threading
         }
 
         return blockDensity;
     }
 
-    static class CacheKey {
+    public static class CacheKey { // Folia - region threading - public
         private final Level world;
         private final double posX, posY, posZ;
         private final double minX, minY, minZ;
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index ca89d1593bf1b46c79a882db528cbca1359dc9d4..2c0ce270c947c7fc1d7e0163a43467129a65f999 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -115,10 +115,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public static final int TICKS_PER_DAY = 24000;
     public static final int MAX_ENTITY_SPAWN_Y = 20000000;
     public static final int MIN_ENTITY_SPAWN_Y = -20000000;
-    public final List<TickingBlockEntity> blockEntityTickers = Lists.newArrayList(); // Paper - public
-    protected final NeighborUpdater neighborUpdater;
-    private final List<TickingBlockEntity> pendingBlockEntityTickers = Lists.newArrayList();
-    private boolean tickingBlockEntities;
+    //public final List<TickingBlockEntity> blockEntityTickers = Lists.newArrayList(); // Paper - public // Folia - region threading
+    public final int neighbourUpdateMax; //protected final NeighborUpdater neighborUpdater; // Folia - region threading
+    //private final List<TickingBlockEntity> pendingBlockEntityTickers = Lists.newArrayList(); // Folia - region threading
+    //private boolean tickingBlockEntities; // Folia - region threading
     public final Thread thread;
     private final boolean isDebug;
     private int skyDarken;
@@ -128,7 +128,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public float rainLevel;
     protected float oThunderLevel;
     public float thunderLevel;
-    public final RandomSource random = RandomSource.create();
+    public final RandomSource random = new Entity.RandomRandomSource(); // Folia - region threading
     /** @deprecated */
     @Deprecated
     private final RandomSource threadSafeRandom = RandomSource.createThreadSafe();
@@ -142,7 +142,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     private final ResourceKey<Level> dimension;
     private final RegistryAccess registryAccess;
     private final DamageSources damageSources;
-    private long subTickCount;
+    private final java.util.concurrent.atomic.AtomicLong subTickCount = new java.util.concurrent.atomic.AtomicLong(); //private long subTickCount; // Folia - region threading
 
     // CraftBukkit start Added the following
     private final CraftWorld world;
@@ -150,20 +150,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public boolean keepSpawnInMemory = true;
     public org.bukkit.generator.ChunkGenerator generator;
 
-    public boolean preventPoiUpdated = false; // CraftBukkit - SPIGOT-5710
-    public boolean captureBlockStates = false;
-    public boolean captureTreeGeneration = false;
-    public Map<BlockPos, org.bukkit.craftbukkit.block.CraftBlockState> capturedBlockStates = new java.util.LinkedHashMap<>(); // Paper
-    public Map<BlockPos, BlockEntity> capturedTileEntities = new java.util.LinkedHashMap<>(); // Paper - Retain block place order when capturing blockstates
-    public List<ItemEntity> captureDrops;
+    // Folia - region threading - moved to regionised data
     public final it.unimi.dsi.fastutil.objects.Object2LongOpenHashMap<SpawnCategory> ticksPerSpawnCategory = new it.unimi.dsi.fastutil.objects.Object2LongOpenHashMap<>();
-    // Paper start
-    public int wakeupInactiveRemainingAnimals;
-    public int wakeupInactiveRemainingFlying;
-    public int wakeupInactiveRemainingMonsters;
-    public int wakeupInactiveRemainingVillagers;
-    // Paper end
-    public boolean populating;
+    // Folia - region threading - moved to regionised data
+    // Folia - region threading
     public final org.spigotmc.SpigotWorldConfig spigotConfig; // Spigot
     // Paper start - add paper world config
     private final io.papermc.paper.configuration.WorldConfiguration paperConfig;
@@ -177,9 +167,9 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public static BlockPos lastPhysicsProblem; // Spigot
     private org.spigotmc.TickLimiter entityLimiter;
     private org.spigotmc.TickLimiter tileLimiter;
-    private int tileTickPosition;
-    public final Map<Explosion.CacheKey, Float> explosionDensityCache = new HashMap<>(); // Paper - Optimize explosions
-    public java.util.ArrayDeque<net.minecraft.world.level.block.RedstoneTorchBlock.Toggle> redstoneUpdateInfos; // Paper - Faster redstone torch rapid clock removal; Move from Map in BlockRedstoneTorch to here
+    //private int tileTickPosition; // Folia - region threading
+    //public final Map<Explosion.CacheKey, Float> explosionDensityCache = new HashMap<>(); // Paper - Optimize explosions // Folia - region threading
+    //public java.util.ArrayDeque<net.minecraft.world.level.block.RedstoneTorchBlock.Toggle> redstoneUpdateInfos; // Paper - Faster redstone torch rapid clock removal; Move from Map in BlockRedstoneTorch to here // Folia - region threading
 
     // Paper start - fix and optimise world upgrading
     // copied from below
@@ -216,6 +206,33 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     public abstract ResourceKey<LevelStem> getTypeKey();
 
+    // Folia start - region ticking
+    public final io.papermc.paper.threadedregions.RegionizedData<io.papermc.paper.threadedregions.RegionizedWorldData> worldRegionData
+        = new io.papermc.paper.threadedregions.RegionizedData<>(
+        (ServerLevel)this, () -> new io.papermc.paper.threadedregions.RegionizedWorldData((ServerLevel)Level.this),
+        io.papermc.paper.threadedregions.RegionizedWorldData.REGION_CALLBACK
+    );
+    public volatile io.papermc.paper.threadedregions.RegionizedServer.WorldLevelData tickData;
+    public final java.util.concurrent.ConcurrentHashMap.KeySetView<net.minecraft.server.level.ChunkHolder, Boolean> needsChangeBroadcasting = java.util.concurrent.ConcurrentHashMap.newKeySet();
+
+    public io.papermc.paper.threadedregions.RegionizedWorldData getCurrentWorldData() {
+        final io.papermc.paper.threadedregions.RegionizedWorldData ret = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        if (ret == null) {
+            return ret;
+        }
+        Level world = ret.world;
+        if (world != this) {
+            throw new IllegalStateException("World mismatch: expected " + this.getWorld().getName() + " but got " + world.getWorld().getName());
+        }
+        return ret;
+    }
+
+    @Override
+    public List<net.minecraft.server.level.ServerPlayer> getLocalPlayers() {
+        return this.getCurrentWorldData().getLocalPlayers();
+    }
+    // Folia end - region ticking
+
     protected Level(WritableLevelData worlddatamutable, ResourceKey<Level> resourcekey, RegistryAccess iregistrycustom, Holder<DimensionType> holder, Supplier<ProfilerFiller> supplier, boolean flag, boolean flag1, long i, int j, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider, org.bukkit.World.Environment env, java.util.function.Function<org.spigotmc.SpigotWorldConfig, io.papermc.paper.configuration.WorldConfiguration> paperWorldConfigCreator, java.util.concurrent.Executor executor) { // Paper - create paper world config; Async-Anti-Xray: Pass executor
         this.spigotConfig = new org.spigotmc.SpigotWorldConfig(((net.minecraft.world.level.storage.PrimaryLevelData) worlddatamutable).getLevelName()); // Spigot
         this.paperConfig = paperWorldConfigCreator.apply(this.spigotConfig); // Paper - create paper world config
@@ -259,7 +276,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         this.thread = Thread.currentThread();
         this.biomeManager = new BiomeManager(this, i);
         this.isDebug = flag1;
-        this.neighborUpdater = new CollectingNeighborUpdater(this, j);
+        this.neighbourUpdateMax = j; // Folia - region threading
         this.registryAccess = iregistrycustom;
         this.damageSources = new DamageSources(iregistrycustom);
         // CraftBukkit start
@@ -848,8 +865,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     @Nullable
     public final BlockState getBlockStateIfLoaded(BlockPos pos) {
         // CraftBukkit start - tree generation
-        if (this.captureTreeGeneration) {
-            CraftBlockState previous = this.capturedBlockStates.get(pos);
+        if (this.getCurrentWorldData().captureTreeGeneration) { // Folia - region threading
+            CraftBlockState previous = this.getCurrentWorldData().capturedBlockStates.get(pos); // Folia - region threading
             if (previous != null) {
                 return previous.getHandle();
             }
@@ -911,16 +928,18 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Override
     public boolean setBlock(BlockPos pos, BlockState state, int flags, int maxUpdateDepth) {
+        io.papermc.paper.util.TickThread.ensureTickThread((ServerLevel)this, pos, "Updating block asynchronously"); // Folia - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.getCurrentWorldData(); // Folia - region threading
         // CraftBukkit start - tree generation
-        if (this.captureTreeGeneration) {
+        if (worldData.captureTreeGeneration) { // Folia - region threading
             // Paper start - Protect Bedrock and End Portal/Frames from being destroyed
             BlockState type = getBlockState(pos);
             if (!type.isDestroyable()) return false;
             // Paper end - Protect Bedrock and End Portal/Frames from being destroyed
-            CraftBlockState blockstate = this.capturedBlockStates.get(pos);
+            CraftBlockState blockstate = worldData.capturedBlockStates.get(pos); // Folia - region threading
             if (blockstate == null) {
                 blockstate = CapturedBlockState.getTreeBlockState(this, pos, flags);
-                this.capturedBlockStates.put(pos.immutable(), blockstate);
+                worldData.capturedBlockStates.put(pos.immutable(), blockstate); // Folia - region threading
             }
             blockstate.setData(state);
             blockstate.setFlag(flags);
@@ -937,10 +956,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
             // CraftBukkit start - capture blockstates
             boolean captured = false;
-            if (this.captureBlockStates && !this.capturedBlockStates.containsKey(pos)) {
+            if (worldData.captureBlockStates && !worldData.capturedBlockStates.containsKey(pos)) { // Folia - region threading
                 CraftBlockState blockstate = (CraftBlockState) world.getBlockAt(pos.getX(), pos.getY(), pos.getZ()).getState(); // Paper - use CB getState to get a suitable snapshot
                 blockstate.setFlag(flags); // Paper - set flag
-                this.capturedBlockStates.put(pos.immutable(), blockstate);
+                worldData.capturedBlockStates.put(pos.immutable(), blockstate); // Folia - region threading
                 captured = true;
             }
             // CraftBukkit end
@@ -950,8 +969,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
             if (iblockdata1 == null) {
                 // CraftBukkit start - remove blockstate if failed (or the same)
-                if (this.captureBlockStates && captured) {
-                    this.capturedBlockStates.remove(pos);
+                if (worldData.captureBlockStates && captured) { // Folia - region threading
+                    worldData.capturedBlockStates.remove(pos); // Folia - region threading
                 }
                 // CraftBukkit end
                 return false;
@@ -988,7 +1007,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
                 */
 
                 // CraftBukkit start
-                if (!this.captureBlockStates) { // Don't notify clients or update physics while capturing blockstates
+                if (!worldData.captureBlockStates) { // Don't notify clients or update physics while capturing blockstates // Folia - region threading
                     // Modularize client and physic updates
                     // Spigot start
                     try {
@@ -1038,7 +1057,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
                 iblockdata1.updateIndirectNeighbourShapes(this, blockposition, k, j - 1); // Don't call an event for the old block to limit event spam
                 CraftWorld world = ((ServerLevel) this).getWorld();
                 boolean cancelledUpdates = false; // Paper - Fix block place logic
-                if (world != null && ((ServerLevel)this).hasPhysicsEvent) { // Paper - BlockPhysicsEvent
+                if (world != null && ((ServerLevel)this).getCurrentWorldData().hasPhysicsEvent) { // Paper - BlockPhysicsEvent // Folia - region threading
                     BlockPhysicsEvent event = new BlockPhysicsEvent(world.getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ()), CraftBlockData.fromData(iblockdata));
                     this.getCraftServer().getPluginManager().callEvent(event);
 
@@ -1052,7 +1071,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
             }
 
             // CraftBukkit start - SPIGOT-5710
-            if (!this.preventPoiUpdated) {
+            if (!this.getCurrentWorldData().preventPoiUpdated) { // Folia - region threading
                 this.onBlockStateChange(blockposition, iblockdata1, iblockdata2);
             }
             // CraftBukkit end
@@ -1136,7 +1155,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Override
     public void neighborShapeChanged(Direction direction, BlockState neighborState, BlockPos pos, BlockPos neighborPos, int flags, int maxUpdateDepth) {
-        this.neighborUpdater.shapeUpdate(direction, neighborState, pos, neighborPos, flags, maxUpdateDepth);
+        this.getCurrentWorldData().neighborUpdater.shapeUpdate(direction, neighborState, pos, neighborPos, flags, maxUpdateDepth); // Folia - region threading
     }
 
     @Override
@@ -1161,11 +1180,34 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         return this.getChunkSource().getLightEngine();
     }
 
+    // Folia start - region threading
+    @Nullable
+    public BlockState getBlockStateFromEmptyChunkIfLoaded(BlockPos pos) {
+        net.minecraft.server.level.ServerChunkCache chunkProvider = (net.minecraft.server.level.ServerChunkCache)this.getChunkSource();
+        ChunkAccess chunk = chunkProvider.getChunkAtImmediately(pos.getX() >> 4, pos.getZ() >> 4);
+        if (chunk != null) {
+            return chunk.getBlockState(pos);
+        }
+        return null;
+    }
+
+    @Nullable
+    public BlockState getBlockStateFromEmptyChunk(BlockPos pos) {
+        net.minecraft.server.level.ServerChunkCache chunkProvider = (net.minecraft.server.level.ServerChunkCache)this.getChunkSource();
+        ChunkAccess chunk = chunkProvider.getChunkAtImmediately(pos.getX() >> 4, pos.getZ() >> 4);
+        if (chunk != null) {
+            return chunk.getBlockState(pos);
+        }
+        chunk = chunkProvider.getChunk(pos.getX() >> 4, pos.getZ() >> 4, ChunkStatus.EMPTY, true);
+        return chunk.getBlockState(pos);
+    }
+    // Folia end - region threading
+
     @Override
     public BlockState getBlockState(BlockPos pos) {
         // CraftBukkit start - tree generation
-        if (this.captureTreeGeneration) {
-            CraftBlockState previous = this.capturedBlockStates.get(pos); // Paper
+        if (this.getCurrentWorldData().captureTreeGeneration) { // Folia - region threading
+            CraftBlockState previous = this.getCurrentWorldData().capturedBlockStates.get(pos); // Paper // Folia - region threading
             if (previous != null) {
                 return previous.getHandle();
             }
@@ -1262,7 +1304,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     }
 
     public void addBlockEntityTicker(TickingBlockEntity ticker) {
-        (this.tickingBlockEntities ? this.pendingBlockEntityTickers : this.blockEntityTickers).add(ticker);
+        ((ServerLevel)this).getCurrentWorldData().addBlockEntityTicker(ticker); // Folia - regionised ticking
     }
 
     protected void tickBlockEntities() {
@@ -1270,11 +1312,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
         gameprofilerfiller.push("blockEntities");
         this.timings.tileEntityPending.startTiming(); // Spigot
-        this.tickingBlockEntities = true;
-        if (!this.pendingBlockEntityTickers.isEmpty()) {
-            this.blockEntityTickers.addAll(this.pendingBlockEntityTickers);
-            this.pendingBlockEntityTickers.clear();
-        }
+        final io.papermc.paper.threadedregions.RegionizedWorldData regionizedWorldData = this.getCurrentWorldData(); // Folia - regionised ticking
+        regionizedWorldData.seTtickingBlockEntities(true); // Folia - regionised ticking
+        regionizedWorldData.pushPendingTickingBlockEntities(); // Folia - regionised ticking
+        List<TickingBlockEntity> blockEntityTickers = regionizedWorldData.getBlockEntityTickers(); // Folia - regionised ticking
         this.timings.tileEntityPending.stopTiming(); // Spigot
 
         this.timings.tileEntityTick.startTiming(); // Spigot
@@ -1285,9 +1326,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         int tilesThisCycle = 0;
         var toRemove = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<TickingBlockEntity>(); // Paper - Fix MC-117075; use removeAll
         toRemove.add(null); // Paper - Fix MC-117075
-        for (tileTickPosition = 0; tileTickPosition < this.blockEntityTickers.size(); tileTickPosition++) { // Paper - Disable tick limiters
-            this.tileTickPosition = (this.tileTickPosition < this.blockEntityTickers.size()) ? this.tileTickPosition : 0;
-            TickingBlockEntity tickingblockentity = (TickingBlockEntity) this.blockEntityTickers.get(this.tileTickPosition);
+        for (int i = 0; i < blockEntityTickers.size(); i++) { // Paper - Disable tick limiters // Folia - regionised ticking
+            TickingBlockEntity tickingblockentity = (TickingBlockEntity) blockEntityTickers.get(i); // Folia - regionised ticking
             // Spigot end
 
             if (tickingblockentity.isRemoved()) {
@@ -1298,19 +1338,19 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
             } else if (flag && this.shouldTickBlocksAt(tickingblockentity.getPos())) {
                 tickingblockentity.tick();
                 // Paper start - execute chunk tasks during tick
-                if ((this.tileTickPosition & 7) == 0) {
+                if ((i & 7) == 0) { // Folia - regionised ticking
                     MinecraftServer.getServer().executeMidTickTasks();
                 }
                 // Paper end - execute chunk tasks during tick
             }
         }
-        this.blockEntityTickers.removeAll(toRemove); // Paper - Fix MC-117075
+        blockEntityTickers.removeAll(toRemove); // Paper - Fix MC-117075 // Folia - regionised ticking
 
         this.timings.tileEntityTick.stopTiming(); // Spigot
-        this.tickingBlockEntities = false;
-        co.aikar.timings.TimingHistory.tileEntityTicks += this.blockEntityTickers.size(); // Paper
+        regionizedWorldData.seTtickingBlockEntities(false); // Folia - regionised ticking
+        //co.aikar.timings.TimingHistory.tileEntityTicks += this.blockEntityTickers.size(); // Paper // Folia - region threading
         gameprofilerfiller.pop();
-        this.spigotConfig.currentPrimedTnt = 0; // Spigot
+        regionizedWorldData.currentPrimedTnt = 0; // Spigot // Folia - region threading
     }
 
     public <T extends Entity> void guardEntityTick(Consumer<T> tickConsumer, T entity) {
@@ -1323,7 +1363,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
             final String msg = String.format("Entity threw exception at %s:%s,%s,%s", entity.level().getWorld().getName(), entity.getX(), entity.getY(), entity.getZ());
             MinecraftServer.LOGGER.error(msg, throwable);
             getCraftServer().getPluginManager().callEvent(new com.destroystokyo.paper.event.server.ServerExceptionEvent(new com.destroystokyo.paper.exception.ServerInternalException(msg, throwable))); // Paper - ServerExceptionEvent
-            entity.discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.DISCARD);
+            if (!(entity instanceof net.minecraft.server.level.ServerPlayer)) entity.discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.DISCARD); // Folia - properly disconnect players
+            if (entity instanceof net.minecraft.server.level.ServerPlayer player) player.connection.disconnect(net.minecraft.network.chat.Component.translatable("multiplayer.disconnect.generic"), org.bukkit.event.player.PlayerKickEvent.Cause.UNKNOWN); // Folia - properly disconnect players
             // Paper end - Prevent block entity and entity crashes
         }
     }
@@ -1423,9 +1464,14 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Nullable
     public BlockEntity getBlockEntity(BlockPos blockposition, boolean validate) {
+        // Folia start - region threading
+        if (!io.papermc.paper.util.TickThread.isTickThread()) {
+            return null;
+        }
+        // Folia end - region threading
         // Paper start - Perf: Optimize capturedTileEntities lookup
         net.minecraft.world.level.block.entity.BlockEntity blockEntity;
-        if (!this.capturedTileEntities.isEmpty() && (blockEntity = this.capturedTileEntities.get(blockposition)) != null) {
+        if (!this.getCurrentWorldData().capturedTileEntities.isEmpty() && (blockEntity = this.getCurrentWorldData().capturedTileEntities.get(blockposition)) != null) { // Folia - region threading
             return blockEntity;
         }
         // Paper end - Perf: Optimize capturedTileEntities lookup
@@ -1438,8 +1484,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
         if (!this.isOutsideBuildHeight(blockposition)) {
             // CraftBukkit start
-            if (this.captureBlockStates) {
-                this.capturedTileEntities.put(blockposition.immutable(), blockEntity);
+            if (this.getCurrentWorldData().captureBlockStates) { // Folia - region threading
+                this.getCurrentWorldData().capturedTileEntities.put(blockposition.immutable(), blockEntity); // Folia - region threading
                 return;
             }
             // CraftBukkit end
@@ -1519,6 +1565,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Override
     public List<Entity> getEntities(@Nullable Entity except, AABB box, Predicate<? super Entity> predicate) {
+        io.papermc.paper.util.TickThread.ensureTickThread((ServerLevel)this, box, "Cannot getEntities asynchronously"); // Folia - region threading
         this.getProfiler().incrementCounter("getEntities");
         List<Entity> list = Lists.newArrayList();
         ((ServerLevel)this).getEntityLookup().getEntities(except, box, list, predicate); // Paper - optimise this call
@@ -1538,6 +1585,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     }
 
     public <T extends Entity> void getEntities(EntityTypeTest<Entity, T> filter, AABB box, Predicate<? super T> predicate, List<? super T> result, int limit) {
+        io.papermc.paper.util.TickThread.ensureTickThread((ServerLevel)this, box, "Cannot getEntities asynchronously"); // Folia - region threading
         this.getProfiler().incrementCounter("getEntities");
         // Paper start - optimise this call
         //TODO use limit
@@ -1575,13 +1623,30 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     public void disconnect() {}
 
+    @Override // Folia - region threading
     public long getGameTime() {
-        return this.levelData.getGameTime();
+        // Dumb world gen thread calls this for some reason. So, check for null.
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.getCurrentWorldData();
+        return worldData == null ? this.getLevelData().getGameTime() : worldData.getTickData().nonRedstoneGameTime();
     }
 
     public long getDayTime() {
-        return this.levelData.getDayTime();
+        // Dumb world gen thread calls this for some reason. So, check for null.
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = this.getCurrentWorldData();
+        return worldData == null ? this.getLevelData().getDayTime() : worldData.getTickData().dayTime();
+    }
+
+    // Folia start - region threading
+    @Override
+    public long dayTime() {
+        return this.getDayTime();
+    }
+
+    @Override
+    public long getRedstoneGameTime() {
+        return this.getCurrentWorldData().getRedstoneGameTime();
     }
+    // Folia end - region threading
 
     public boolean mayInteract(Player player, BlockPos pos) {
         return true;
@@ -1785,8 +1850,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     }
     public final BlockPos.MutableBlockPos getRandomBlockPosition(int x, int y, int z, int l, BlockPos.MutableBlockPos out) {
         // Paper end
-        this.randValue = this.randValue * 3 + 1013904223;
-        int i1 = this.randValue >> 2;
+        int i1 = this.random.nextInt() >> 2; // Folia - region threading
 
         out.set(x + (i1 & 15), y + (i1 >> 16 & l), z + (i1 >> 8 & 15)); // Paper - change to setValues call
         return out; // Paper
@@ -1817,7 +1881,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Override
     public long nextSubTickCount() {
-        return (long) (this.subTickCount++);
+        return this.subTickCount.getAndIncrement(); // Folia - region threading
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/world/level/LevelAccessor.java b/src/main/java/net/minecraft/world/level/LevelAccessor.java
index bd9ac874b2d4333bc5c3a79657d63f1bd41fd8c8..f706159a85fe463806b44c768dc9d438a6a1d958 100644
--- a/src/main/java/net/minecraft/world/level/LevelAccessor.java
+++ b/src/main/java/net/minecraft/world/level/LevelAccessor.java
@@ -35,12 +35,22 @@ public interface LevelAccessor extends CommonLevelAccessor, LevelTimeAccess {
 
     LevelTickAccess<Block> getBlockTicks();
 
+    // Folia start - region threading
+    default long getGameTime() {
+        return this.getLevelData().getGameTime();
+    }
+
+    default long getRedstoneGameTime() {
+        return this.getLevelData().getGameTime();
+    }
+    // Folia end - region threading
+
     default <T> ScheduledTick<T> createTick(BlockPos pos, T type, int delay, TickPriority priority) { // CraftBukkit - decompile error
-        return new ScheduledTick<>(type, pos, this.getLevelData().getGameTime() + (long) delay, priority, this.nextSubTickCount());
+        return new ScheduledTick<>(type, pos, this.getRedstoneGameTime() + (long) delay, priority, this.nextSubTickCount()); // Folia - region threading
     }
 
     default <T> ScheduledTick<T> createTick(BlockPos pos, T type, int delay) { // CraftBukkit - decompile error
-        return new ScheduledTick<>(type, pos, this.getLevelData().getGameTime() + (long) delay, this.nextSubTickCount());
+        return new ScheduledTick<>(type, pos, this.getRedstoneGameTime() + (long) delay, this.nextSubTickCount()); // Folia - region threading
     }
 
     default void scheduleTick(BlockPos pos, Block block, int delay, TickPriority priority) {
diff --git a/src/main/java/net/minecraft/world/level/LevelReader.java b/src/main/java/net/minecraft/world/level/LevelReader.java
index dab86988686cf7c926b7432b8a4afffd7a23327a..a956c88b82ca39c18f933369c8db2df8722a2e2c 100644
--- a/src/main/java/net/minecraft/world/level/LevelReader.java
+++ b/src/main/java/net/minecraft/world/level/LevelReader.java
@@ -205,6 +205,25 @@ public interface LevelReader extends BlockAndTintGetter, CollisionGetter, Signal
         return maxY >= this.getMinBuildHeight() && minY < this.getMaxBuildHeight() && this.hasChunksAt(minX, minZ, maxX, maxZ);
     }
 
+    // Folia start - region threading
+    default boolean hasAndOwnsChunksAt(int minX, int minZ, int maxX, int maxZ) {
+        int i = SectionPos.blockToSectionCoord(minX);
+        int j = SectionPos.blockToSectionCoord(maxX);
+        int k = SectionPos.blockToSectionCoord(minZ);
+        int l = SectionPos.blockToSectionCoord(maxZ);
+
+        for(int m = i; m <= j; ++m) {
+            for(int n = k; n <= l; ++n) {
+                if (!this.hasChunk(m, n) || (this instanceof net.minecraft.server.level.ServerLevel world && !io.papermc.paper.util.TickThread.isTickThreadFor(world, m, n))) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+    // Folia end - region threading
+
     @Deprecated
     default boolean hasChunksAt(int minX, int minZ, int maxX, int maxZ) {
         int i = SectionPos.blockToSectionCoord(minX);
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index da7489986848316fed029b71d1bc4e1248c9c9a8..9c1263fdc3731e04ac28c6d0ed904ecdc3ea3038 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -146,7 +146,7 @@ public final class NaturalSpawner {
             int limit = enumcreaturetype.getMaxInstancesPerChunk();
             SpawnCategory spawnCategory = CraftSpawnCategory.toBukkit(enumcreaturetype);
             if (CraftSpawnCategory.isValidForLimits(spawnCategory)) {
-                spawnThisTick = world.ticksPerSpawnCategory.getLong(spawnCategory) != 0 && worlddata.getGameTime() % world.ticksPerSpawnCategory.getLong(spawnCategory) == 0;
+                spawnThisTick = world.ticksPerSpawnCategory.getLong(spawnCategory) != 0 && world.getRedstoneGameTime() % world.ticksPerSpawnCategory.getLong(spawnCategory) == 0; // Folia - region threading
                 limit = world.getWorld().getSpawnLimit(spawnCategory);
             }
 
diff --git a/src/main/java/net/minecraft/world/level/ServerLevelAccessor.java b/src/main/java/net/minecraft/world/level/ServerLevelAccessor.java
index 3d377b9e461040405e0a7dcbd72d1506b48eb44e..782890e227ff9dab44dd92327979c201985f116e 100644
--- a/src/main/java/net/minecraft/world/level/ServerLevelAccessor.java
+++ b/src/main/java/net/minecraft/world/level/ServerLevelAccessor.java
@@ -7,6 +7,12 @@ public interface ServerLevelAccessor extends LevelAccessor {
 
     ServerLevel getLevel();
 
+    // Folia start - region threading
+    default public StructureManager structureManager() {
+        throw new UnsupportedOperationException();
+    }
+    // Folia end - region threading
+
     default void addFreshEntityWithPassengers(Entity entity) {
         // CraftBukkit start
         this.addFreshEntityWithPassengers(entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT);
diff --git a/src/main/java/net/minecraft/world/level/StructureManager.java b/src/main/java/net/minecraft/world/level/StructureManager.java
index 07eb481380e8fd4e492f36342ba633579c1b624e..9f3a8f26f4ecd33ea0e4c82a40c9432c094ac899 100644
--- a/src/main/java/net/minecraft/world/level/StructureManager.java
+++ b/src/main/java/net/minecraft/world/level/StructureManager.java
@@ -46,11 +46,7 @@ public class StructureManager {
     }
 
     public List<StructureStart> startsForStructure(ChunkPos pos, Predicate<Structure> predicate) {
-        // Paper start - Fix swamp hut cat generation deadlock
-        return this.startsForStructure(pos, predicate, null);
-    }
-    public List<StructureStart> startsForStructure(ChunkPos pos, Predicate<Structure> predicate, @Nullable ServerLevelAccessor levelAccessor) {
-        Map<Structure, LongSet> map = (levelAccessor == null ? this.level : levelAccessor).getChunk(pos.x, pos.z, ChunkStatus.STRUCTURE_REFERENCES).getAllReferences();
+        Map<Structure, LongSet> map = this.level.getChunk(pos.x, pos.z, ChunkStatus.STRUCTURE_REFERENCES).getAllReferences(); // Folia - region threading
         // Paper end - Fix swamp hut cat generation deadlock
         Builder<StructureStart> builder = ImmutableList.builder();
 
@@ -116,15 +112,11 @@ public class StructureManager {
     }
 
     public StructureStart getStructureWithPieceAt(BlockPos pos, TagKey<Structure> structureTag) {
-        // Paper start - Fix swamp hut cat generation deadlock
-        return this.getStructureWithPieceAt(pos, structureTag, null);
-    }
-    public StructureStart getStructureWithPieceAt(BlockPos pos, TagKey<Structure> structureTag, @Nullable ServerLevelAccessor levelAccessor) {
-        // Paper end - Fix swamp hut cat generation deadlock
+        // Folia - region threading
         Registry<Structure> registry = this.registryAccess().registryOrThrow(Registries.STRUCTURE);
 
         for (StructureStart structureStart : this.startsForStructure(
-            new ChunkPos(pos), structure -> registry.getHolder(registry.getId(structure)).map(reference -> reference.is(structureTag)).orElse(false), levelAccessor // Paper - Fix swamp hut cat generation deadlock
+            new ChunkPos(pos), structure -> registry.getHolder(registry.getId(structure)).map(reference -> reference.is(structureTag)).orElse(false) // Paper - Fix swamp hut cat generation deadlock // Folia - region threading
         )) {
             if (this.structureHasPieceAt(pos, structureStart)) {
                 return structureStart;
@@ -169,7 +161,7 @@ public class StructureManager {
     }
 
     public void addReference(StructureStart structureStart) {
-        structureStart.addReference();
+        //structureStart.addReference(); // Folia - region threading - move to caller
         this.structureCheck.incrementReference(structureStart.getChunkPos(), structureStart.getStructure());
     }
 
diff --git a/src/main/java/net/minecraft/world/level/block/BedBlock.java b/src/main/java/net/minecraft/world/level/block/BedBlock.java
index 38fcde81d797dc46409f5a9ed426fe296d79bdfa..11ba667fd0fe79513d505b34eb0cf1ec66fc2842 100644
--- a/src/main/java/net/minecraft/world/level/block/BedBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/BedBlock.java
@@ -367,7 +367,7 @@ public class BedBlock extends HorizontalDirectionalBlock implements EntityBlock
 
             world.setBlock(blockposition1, (BlockState) state.setValue(BedBlock.PART, BedPart.HEAD), 3);
             // CraftBukkit start - SPIGOT-7315: Don't updated if we capture block states
-            if (world.captureBlockStates) {
+            if (world.getCurrentWorldData().captureBlockStates) { // Folia - region threading
                 return;
             }
             // CraftBukkit end
diff --git a/src/main/java/net/minecraft/world/level/block/Block.java b/src/main/java/net/minecraft/world/level/block/Block.java
index 22036ed3ea0629bc12981a8d91a03e55cc2117d6..6df3913145aaf37f9a1b7dc77fed12f6952d77e6 100644
--- a/src/main/java/net/minecraft/world/level/block/Block.java
+++ b/src/main/java/net/minecraft/world/level/block/Block.java
@@ -398,8 +398,8 @@ public class Block extends BlockBehaviour implements ItemLike {
 
             entityitem.setDefaultPickUpDelay();
             // CraftBukkit start
-            if (world.captureDrops != null) {
-                world.captureDrops.add(entityitem);
+            if (world.getCurrentWorldData().captureDrops != null) { // Folia - region threading
+                world.getCurrentWorldData().captureDrops.add(entityitem); // Folia - region threading
             } else {
                 world.addFreshEntity(entityitem);
             }
diff --git a/src/main/java/net/minecraft/world/level/block/BushBlock.java b/src/main/java/net/minecraft/world/level/block/BushBlock.java
index bed3d9c781c7d3ca260027b4737970889a54689c..46c81d73813c6607d95062358e6e3cd05ffe3192 100644
--- a/src/main/java/net/minecraft/world/level/block/BushBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/BushBlock.java
@@ -28,7 +28,7 @@ public abstract class BushBlock extends Block {
     public BlockState updateShape(BlockState state, Direction direction, BlockState neighborState, LevelAccessor world, BlockPos pos, BlockPos neighborPos) {
         // CraftBukkit start
         if (!state.canSurvive(world, pos)) {
-            if (!(world instanceof net.minecraft.server.level.ServerLevel && ((net.minecraft.server.level.ServerLevel) world).hasPhysicsEvent) || !org.bukkit.craftbukkit.event.CraftEventFactory.callBlockPhysicsEvent(world, pos).isCancelled()) { // Paper
+            if (!(world instanceof net.minecraft.server.level.ServerLevel && ((net.minecraft.server.level.ServerLevel) world).getCurrentWorldData().hasPhysicsEvent) || !org.bukkit.craftbukkit.event.CraftEventFactory.callBlockPhysicsEvent(world, pos).isCancelled()) { // Paper // Folia - region threading
                 return Blocks.AIR.defaultBlockState();
             }
         }
diff --git a/src/main/java/net/minecraft/world/level/block/DaylightDetectorBlock.java b/src/main/java/net/minecraft/world/level/block/DaylightDetectorBlock.java
index de6f00d03223939386aa2ccfdec1e696a68313d7..eb7c2c5b762dbadbe9ccbddc37757bdf97ea4bfe 100644
--- a/src/main/java/net/minecraft/world/level/block/DaylightDetectorBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DaylightDetectorBlock.java
@@ -120,7 +120,7 @@ public class DaylightDetectorBlock extends BaseEntityBlock {
     }
 
     private static void tickEntity(Level world, BlockPos pos, BlockState state, DaylightDetectorBlockEntity blockEntity) {
-        if (world.getGameTime() % 20L == 0L) {
+        if (world.getRedstoneGameTime() % 20L == 0L) { // Folia - region threading
             DaylightDetectorBlock.updateSignalStrength(state, world, pos);
         }
 
diff --git a/src/main/java/net/minecraft/world/level/block/DispenserBlock.java b/src/main/java/net/minecraft/world/level/block/DispenserBlock.java
index 644e64850479cea20a98b8a65503ccf3a34fd32a..321779653c5b1f528673b7aad01f544cc200be58 100644
--- a/src/main/java/net/minecraft/world/level/block/DispenserBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DispenserBlock.java
@@ -49,7 +49,7 @@ public class DispenserBlock extends BaseEntityBlock {
         object2objectopenhashmap.defaultReturnValue(new DefaultDispenseItemBehavior());
     });
     private static final int TRIGGER_DURATION = 4;
-    public static boolean eventFired = false; // CraftBukkit
+    public static ThreadLocal<Boolean> eventFired = ThreadLocal.withInitial(() -> Boolean.FALSE); // CraftBukkit // Folia - region threading
 
     @Override
     public MapCodec<? extends DispenserBlock> codec() {
@@ -105,7 +105,7 @@ public class DispenserBlock extends BaseEntityBlock {
 
                 if (idispensebehavior != DispenseItemBehavior.NOOP) {
                     if (!org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockPreDispenseEvent(world, pos, itemstack, i)) return; // Paper - Add BlockPreDispenseEvent
-                    DispenserBlock.eventFired = false; // CraftBukkit - reset event status
+                    DispenserBlock.eventFired.set(Boolean.FALSE); // CraftBukkit - reset event status // Folia - region threading
                     tileentitydispenser.setItem(i, idispensebehavior.dispense(sourceblock, itemstack));
                 }
 
diff --git a/src/main/java/net/minecraft/world/level/block/DoublePlantBlock.java b/src/main/java/net/minecraft/world/level/block/DoublePlantBlock.java
index 03b5ab8251497c0c94467f90e6663a0dc766babb..4fb595a8300ce2b163540603c7a2b002869a84c1 100644
--- a/src/main/java/net/minecraft/world/level/block/DoublePlantBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DoublePlantBlock.java
@@ -102,7 +102,7 @@ public class DoublePlantBlock extends BushBlock {
 
     protected static void preventDropFromBottomPart(Level world, BlockPos pos, BlockState state, Player player) {
         // CraftBukkit start
-        if (((net.minecraft.server.level.ServerLevel)world).hasPhysicsEvent && org.bukkit.craftbukkit.event.CraftEventFactory.callBlockPhysicsEvent(world, pos).isCancelled()) { // Paper
+        if (((net.minecraft.server.level.ServerLevel)world).getCurrentWorldData().hasPhysicsEvent && org.bukkit.craftbukkit.event.CraftEventFactory.callBlockPhysicsEvent(world, pos).isCancelled()) { // Paper // Folia - region threading
             return;
         }
         // CraftBukkit end
diff --git a/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java b/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
index 4ba24bced9a2de4616a0418857d3738e0e322ea0..afc9445941b984cc1122839e4a8a17cf27aa966e 100644
--- a/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
@@ -64,7 +64,7 @@ public class EndPortalBlock extends BaseEntityBlock {
             // Paper start - move all of this logic into portal tick
             entity.portalWorld = ((ServerLevel)world);
             entity.portalBlock = pos.immutable();
-            if (io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowUnsafeEndPortalTeleportation) {
+            if (false) { // Folia - region threading - synchronous teleports are not allowed
                 entity.tickEndPortal();
             }
             // Paper end - move all of this logic into portal tick
diff --git a/src/main/java/net/minecraft/world/level/block/FarmBlock.java b/src/main/java/net/minecraft/world/level/block/FarmBlock.java
index 6e4c852c93f2418ea69e485ed3a10cbe3a6e3bd2..ab2b9b85b844cf3e6ef5a0379fa3279b85a7328c 100644
--- a/src/main/java/net/minecraft/world/level/block/FarmBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/FarmBlock.java
@@ -92,8 +92,8 @@ public class FarmBlock extends Block {
     @Override
     public void randomTick(BlockState state, ServerLevel world, BlockPos pos, RandomSource random) {
         int i = (Integer) state.getValue(FarmBlock.MOISTURE);
-        if (i > 0 && world.paperConfig().tickRates.wetFarmland != 1 && (world.paperConfig().tickRates.wetFarmland < 1 || (net.minecraft.server.MinecraftServer.currentTick + pos.hashCode()) % world.paperConfig().tickRates.wetFarmland != 0)) { return; } // Paper - Configurable random tick rates for blocks
-        if (i == 0 && world.paperConfig().tickRates.dryFarmland != 1 && (world.paperConfig().tickRates.dryFarmland < 1 || (net.minecraft.server.MinecraftServer.currentTick + pos.hashCode()) % world.paperConfig().tickRates.dryFarmland != 0)) { return; } // Paper - Configurable random tick rates for blocks
+        if (i > 0 && world.paperConfig().tickRates.wetFarmland != 1 && (world.paperConfig().tickRates.wetFarmland < 1 || (world.getRedstoneGameTime() + pos.hashCode()) % world.paperConfig().tickRates.wetFarmland != 0)) { return; } // Paper - Configurable random tick rates for blocks // Folia - region threading
+        if (i == 0 && world.paperConfig().tickRates.dryFarmland != 1 && (world.paperConfig().tickRates.dryFarmland < 1 || (world.getRedstoneGameTime() + pos.hashCode()) % world.paperConfig().tickRates.dryFarmland != 0)) { return; } // Paper - Configurable random tick rates for blocks // Folia - region threading
 
         if (!FarmBlock.isNearWater(world, pos) && !world.isRainingAt(pos.above())) {
             if (i > 0) {
diff --git a/src/main/java/net/minecraft/world/level/block/FungusBlock.java b/src/main/java/net/minecraft/world/level/block/FungusBlock.java
index 50d7235cf2ef036451db708c45a063d037051ae9..c0433491be43bb8cc6d00e32edf7699a79f7a251 100644
--- a/src/main/java/net/minecraft/world/level/block/FungusBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/FungusBlock.java
@@ -76,9 +76,9 @@ public class FungusBlock extends BushBlock implements BonemealableBlock {
         this.getFeature(world).ifPresent((holder) -> {
             // CraftBukkit start
             if (this == Blocks.WARPED_FUNGUS) {
-                SaplingBlock.treeType = org.bukkit.TreeType.WARPED_FUNGUS;
+                SaplingBlock.treeTypeRT.set(org.bukkit.TreeType.WARPED_FUNGUS); // Folia - region threading
             } else if (this == Blocks.CRIMSON_FUNGUS) {
-                SaplingBlock.treeType = org.bukkit.TreeType.CRIMSON_FUNGUS;
+                SaplingBlock.treeTypeRT.set(org.bukkit.TreeType.CRIMSON_FUNGUS); // Folia - region threading
             }
             // CraftBukkit end
             ((ConfiguredFeature) holder.value()).place(world, world.getChunkSource().getGenerator(), random, pos);
diff --git a/src/main/java/net/minecraft/world/level/block/HoneyBlock.java b/src/main/java/net/minecraft/world/level/block/HoneyBlock.java
index 409b4818840916a8ddbfc1ee87c8c22902939f38..c1f6922168f5d996e80aeb4035822d5506712b6b 100644
--- a/src/main/java/net/minecraft/world/level/block/HoneyBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/HoneyBlock.java
@@ -86,7 +86,7 @@ public class HoneyBlock extends HalfTransparentBlock {
     }
 
     private void maybeDoSlideAchievement(Entity entity, BlockPos pos) {
-        if (entity instanceof ServerPlayer && entity.level().getGameTime() % 20L == 0L) {
+        if (entity instanceof ServerPlayer && entity.level().getRedstoneGameTime() % 20L == 0L) { // Folia - region threading
             CriteriaTriggers.HONEY_BLOCK_SLIDE.trigger((ServerPlayer)entity, entity.level().getBlockState(pos));
         }
     }
diff --git a/src/main/java/net/minecraft/world/level/block/LightningRodBlock.java b/src/main/java/net/minecraft/world/level/block/LightningRodBlock.java
index ec4aaaca2160312452d724dc6639ac8c4fa42ae4..e1f67599724f67f4f1321f219af8099e8c54e9e7 100644
--- a/src/main/java/net/minecraft/world/level/block/LightningRodBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/LightningRodBlock.java
@@ -119,7 +119,7 @@ public class LightningRodBlock extends RodBlock implements SimpleWaterloggedBloc
 
     @Override
     public void animateTick(BlockState state, Level world, BlockPos pos, RandomSource random) {
-        if (world.isThundering() && (long) world.random.nextInt(200) <= world.getGameTime() % 200L && pos.getY() == world.getHeight(Heightmap.Types.WORLD_SURFACE, pos.getX(), pos.getZ()) - 1) {
+        if (world.isThundering() && (long) world.random.nextInt(200) <= world.getRedstoneGameTime() % 200L && pos.getY() == world.getHeight(Heightmap.Types.WORLD_SURFACE, pos.getX(), pos.getZ()) - 1) { // Folia - region threading
             ParticleUtils.spawnParticlesAlongAxis(((Direction) state.getValue(LightningRodBlock.FACING)).getAxis(), world, pos, 0.125D, ParticleTypes.ELECTRIC_SPARK, UniformInt.of(1, 2));
         }
     }
diff --git a/src/main/java/net/minecraft/world/level/block/MushroomBlock.java b/src/main/java/net/minecraft/world/level/block/MushroomBlock.java
index 1f27ae8abd5891a0b8057b454f2210b088b4e95a..a978a6130f5f6fdd1dab194e753cbe2491713c9d 100644
--- a/src/main/java/net/minecraft/world/level/block/MushroomBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/MushroomBlock.java
@@ -105,7 +105,7 @@ public class MushroomBlock extends BushBlock implements BonemealableBlock {
             return false;
         } else {
             world.removeBlock(pos, false);
-            SaplingBlock.treeType = (this == Blocks.BROWN_MUSHROOM) ? TreeType.BROWN_MUSHROOM : TreeType.RED_MUSHROOM; // CraftBukkit
+            SaplingBlock.treeTypeRT.set((this == Blocks.BROWN_MUSHROOM) ? TreeType.BROWN_MUSHROOM : TreeType.RED_MUSHROOM); // CraftBukkit // Folia - region threading
             if (((ConfiguredFeature) ((Holder) optional.get()).value()).place(world, world.getChunkSource().getGenerator(), random, pos)) {
                 return true;
             } else {
diff --git a/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java b/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
index b5a71fd4e2f55bf036c2c697da5d50cc90fc657c..7f33db05284a957690eac6eb6f5b3b05586727bb 100644
--- a/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
@@ -69,7 +69,7 @@ public class RedStoneWireBlock extends Block {
     });
     private static final float PARTICLE_DENSITY = 0.2F;
     private final BlockState crossState;
-    public boolean shouldSignal = true;
+    //public boolean shouldSignal = true; // Folia - region threading - move to regionised world data
 
     @Override
     public MapCodec<RedStoneWireBlock> codec() {
@@ -261,7 +261,11 @@ public class RedStoneWireBlock extends Block {
 
     // Paper start - Optimize redstone (Eigencraft)
     // The bulk of the new functionality is found in RedstoneWireTurbo.java
-    com.destroystokyo.paper.util.RedstoneWireTurbo turbo = new com.destroystokyo.paper.util.RedstoneWireTurbo(this);
+    // Folia start - region threading
+    private com.destroystokyo.paper.util.RedstoneWireTurbo getTurbo(Level world) {
+        return world.getCurrentWorldData().turbo;
+    }
+    // Folia end - region threading
 
     /*
      * Modified version of pre-existing updateSurroundingRedstone, which is called from
@@ -270,7 +274,7 @@ public class RedStoneWireBlock extends Block {
      */
     private void updateSurroundingRedstone(Level worldIn, BlockPos pos, BlockState state, BlockPos source) {
         if (worldIn.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.EIGENCRAFT) {
-            turbo.updateSurroundingRedstone(worldIn, pos, state, source);
+            this.getTurbo(worldIn).updateSurroundingRedstone(worldIn, pos, state, source); // Folia - region threading
             return;
         }
         updatePowerStrength(worldIn, pos, state);
@@ -289,9 +293,9 @@ public class RedStoneWireBlock extends Block {
         int i = state.getValue(POWER);
         int j = 0;
         j = this.getPower(j, worldIn.getBlockState(pos2));
-        this.shouldSignal = false;
+        io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal = false; // Folia - region threading
         int k = worldIn.getBestNeighborSignal(pos1);
-        this.shouldSignal = true;
+        io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal = true; // Folia - region threading
 
         if (worldIn.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA) {
             // This code is totally redundant to if statements just below the loop.
@@ -361,7 +365,7 @@ public class RedStoneWireBlock extends Block {
                 // [Space Walker] suppress shape updates and emit those manually to
                 // bypass the new neighbor update stack.
                 if (worldIn.setBlock(pos1, state, Block.UPDATE_KNOWN_SHAPE | Block.UPDATE_CLIENTS))
-                    turbo.updateNeighborShapes(worldIn, pos1, state);
+                    this.getTurbo(worldIn).updateNeighborShapes(worldIn, pos1, state); // Folia - region threading
             }
         }
 
@@ -410,10 +414,10 @@ public class RedStoneWireBlock extends Block {
     }
 
     private int calculateTargetStrength(Level world, BlockPos pos) {
-        this.shouldSignal = false;
+        io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal = false; // Folia - region threading
         int i = world.getBestNeighborSignal(pos);
 
-        this.shouldSignal = true;
+        io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal = true; // Folia - region threading
         int j = 0;
 
         if (i < 15) {
@@ -552,12 +556,12 @@ public class RedStoneWireBlock extends Block {
 
     @Override
     public int getDirectSignal(BlockState state, BlockGetter world, BlockPos pos, Direction direction) {
-        return !this.shouldSignal ? 0 : state.getSignal(world, pos, direction);
+        return !io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal ? 0 : state.getSignal(world, pos, direction); // Folia - region threading
     }
 
     @Override
     public int getSignal(BlockState state, BlockGetter world, BlockPos pos, Direction direction) {
-        if (this.shouldSignal && direction != Direction.DOWN) {
+        if (io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData().shouldSignal && direction != Direction.DOWN) { // Folia - region threading
             int i = (Integer) state.getValue(RedStoneWireBlock.POWER);
 
             return i == 0 ? 0 : (direction != Direction.UP && !((RedstoneSide) this.getConnectionState(world, state, pos).getValue((Property) RedStoneWireBlock.PROPERTY_BY_DIRECTION.get(direction.getOpposite()))).isConnected() ? 0 : i);
@@ -584,7 +588,10 @@ public class RedStoneWireBlock extends Block {
 
     @Override
     public boolean isSignalSource(BlockState state) {
-        return this.shouldSignal;
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData();
+        return worldData == null || worldData.shouldSignal;
+        // Folia end - region threading
     }
 
     public static int getColorForPower(int powerLevel) {
diff --git a/src/main/java/net/minecraft/world/level/block/RedstoneTorchBlock.java b/src/main/java/net/minecraft/world/level/block/RedstoneTorchBlock.java
index 1dbfda52a4423fb031eecad24e5766f49ecf6050..332f606d9a41ab19707f2f11bd43d2880b410180 100644
--- a/src/main/java/net/minecraft/world/level/block/RedstoneTorchBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/RedstoneTorchBlock.java
@@ -81,10 +81,10 @@ public class RedstoneTorchBlock extends BaseTorchBlock {
     public void tick(BlockState state, ServerLevel world, BlockPos pos, RandomSource random) {
         boolean flag = this.hasNeighborSignal(world, pos, state);
         // Paper start - Faster redstone torch rapid clock removal
-        java.util.ArrayDeque<RedstoneTorchBlock.Toggle> redstoneUpdateInfos = world.redstoneUpdateInfos;
+        java.util.ArrayDeque<RedstoneTorchBlock.Toggle> redstoneUpdateInfos = world.getCurrentWorldData().redstoneUpdateInfos; // Folia - region threading
         if (redstoneUpdateInfos != null) {
             RedstoneTorchBlock.Toggle curr;
-            while ((curr = redstoneUpdateInfos.peek()) != null && world.getGameTime() - curr.when > 60L) {
+            while ((curr = redstoneUpdateInfos.peek()) != null && world.getRedstoneGameTime() - curr.when > 60L) { // Folia - region threading
                 redstoneUpdateInfos.poll();
             }
         }
@@ -165,14 +165,14 @@ public class RedstoneTorchBlock extends BaseTorchBlock {
 
     private static boolean isToggledTooFrequently(Level world, BlockPos pos, boolean addNew) {
         // Paper start - Faster redstone torch rapid clock removal
-        java.util.ArrayDeque<RedstoneTorchBlock.Toggle> list = world.redstoneUpdateInfos;
+        java.util.ArrayDeque<RedstoneTorchBlock.Toggle> list = world.getCurrentWorldData().redstoneUpdateInfos; // Folia - region threading
         if (list == null) {
-            list = world.redstoneUpdateInfos = new java.util.ArrayDeque<>();
+            list = world.getCurrentWorldData().redstoneUpdateInfos = new java.util.ArrayDeque<>(); // Folia - region threading
         }
         // Paper end - Faster redstone torch rapid clock removal
 
         if (addNew) {
-            list.add(new RedstoneTorchBlock.Toggle(pos.immutable(), world.getGameTime()));
+            list.add(new RedstoneTorchBlock.Toggle(pos.immutable(), world.getRedstoneGameTime())); // Folia - region threading
         }
 
         int i = 0;
@@ -194,12 +194,18 @@ public class RedstoneTorchBlock extends BaseTorchBlock {
 
     public static class Toggle {
 
-        final BlockPos pos;
-        final long when;
+        public final BlockPos pos; // Folia - region threading
+        long when; // Folia - region ticking
 
         public Toggle(BlockPos pos, long time) {
             this.pos = pos;
             this.when = time;
         }
+
+        // Folia start - region ticking
+        public void offsetTime(long offset) {
+            this.when += offset;
+        }
+        // Folia end - region ticking
     }
 }
diff --git a/src/main/java/net/minecraft/world/level/block/SaplingBlock.java b/src/main/java/net/minecraft/world/level/block/SaplingBlock.java
index 3ff0d08e4964aae82d8e51d3b8bf9aa002096f81..d4e86aa35a36ce0ef2cac3567e044b78fa58c87e 100644
--- a/src/main/java/net/minecraft/world/level/block/SaplingBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/SaplingBlock.java
@@ -35,7 +35,7 @@ public class SaplingBlock extends BushBlock implements BonemealableBlock {
     protected static final float AABB_OFFSET = 6.0F;
     protected static final VoxelShape SHAPE = Block.box(2.0D, 0.0D, 2.0D, 14.0D, 12.0D, 14.0D);
     protected final TreeGrower treeGrower;
-    public static TreeType treeType; // CraftBukkit
+    public static final ThreadLocal<TreeType> treeTypeRT = new ThreadLocal<>(); // CraftBukkit // Folia - region threading
 
     @Override
     public MapCodec<? extends SaplingBlock> codec() {
@@ -66,18 +66,19 @@ public class SaplingBlock extends BushBlock implements BonemealableBlock {
             world.setBlock(pos, (net.minecraft.world.level.block.state.BlockState) state.cycle(SaplingBlock.STAGE), 4);
         } else {
             // CraftBukkit start
-            if (world.captureTreeGeneration) {
+            io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+            if (worldData.captureTreeGeneration) { // Folia - region threading
                 this.treeGrower.growTree(world, world.getChunkSource().getGenerator(), pos, state, random);
             } else {
-                world.captureTreeGeneration = true;
+                worldData.captureTreeGeneration = true; // Folia - region threading
                 this.treeGrower.growTree(world, world.getChunkSource().getGenerator(), pos, state, random);
-                world.captureTreeGeneration = false;
-                if (world.capturedBlockStates.size() > 0) {
-                    TreeType treeType = SaplingBlock.treeType;
-                    SaplingBlock.treeType = null;
+                worldData.captureTreeGeneration = false; // Folia - region threading
+                if (worldData.capturedBlockStates.size() > 0) { // Folia - region threading
+                    TreeType treeType = SaplingBlock.treeTypeRT.get(); // Folia - region threading
+                    SaplingBlock.treeTypeRT.set(null); // Folia - region threading
                     Location location = CraftLocation.toBukkit(pos, world.getWorld());
-                    java.util.List<BlockState> blocks = new java.util.ArrayList<>(world.capturedBlockStates.values());
-                    world.capturedBlockStates.clear();
+                    java.util.List<BlockState> blocks = new java.util.ArrayList<>(worldData.capturedBlockStates.values()); // Folia - region threading
+                    worldData.capturedBlockStates.clear(); // Folia - region threading
                     StructureGrowEvent event = null;
                     if (treeType != null) {
                         event = new StructureGrowEvent(location, treeType, false, null, blocks);
diff --git a/src/main/java/net/minecraft/world/level/block/SpreadingSnowyDirtBlock.java b/src/main/java/net/minecraft/world/level/block/SpreadingSnowyDirtBlock.java
index f3003a3832deff7724d28b4b3a091f4802a4cb29..d628cee1f72ee973bc10a49f2dd65becab85e28c 100644
--- a/src/main/java/net/minecraft/world/level/block/SpreadingSnowyDirtBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/SpreadingSnowyDirtBlock.java
@@ -55,7 +55,7 @@ public abstract class SpreadingSnowyDirtBlock extends SnowyDirtBlock {
 
     @Override
     public void randomTick(BlockState state, ServerLevel world, BlockPos pos, RandomSource random) {
-        if (this instanceof GrassBlock && world.paperConfig().tickRates.grassSpread != 1 && (world.paperConfig().tickRates.grassSpread < 1 || (MinecraftServer.currentTick + pos.hashCode()) % world.paperConfig().tickRates.grassSpread != 0)) { return; } // Paper - Configurable random tick rates for blocks
+        if (this instanceof GrassBlock && world.paperConfig().tickRates.grassSpread != 1 && (world.paperConfig().tickRates.grassSpread < 1 || (io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + pos.hashCode()) % world.paperConfig().tickRates.grassSpread != 0)) { return; } // Paper - Configurable random tick rates for blocks // Folia - regionised ticking
         // Paper start - Perf: optimize dirt and snow spreading
         net.minecraft.world.level.chunk.ChunkAccess cachedBlockChunk = world.getChunkIfLoaded(pos);
         if (cachedBlockChunk == null) { // Is this needed?
diff --git a/src/main/java/net/minecraft/world/level/block/WitherSkullBlock.java b/src/main/java/net/minecraft/world/level/block/WitherSkullBlock.java
index fb180f0bcd20e51d41cfc924029c0b23d3d26258..3db0727cd8d835e8d1b7b3fab93613d2e97b95ab 100644
--- a/src/main/java/net/minecraft/world/level/block/WitherSkullBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/WitherSkullBlock.java
@@ -58,7 +58,7 @@ public class WitherSkullBlock extends SkullBlock {
     }
 
     public static void checkSpawn(Level world, BlockPos pos, SkullBlockEntity blockEntity) {
-        if (world.captureBlockStates) return; // CraftBukkit
+        if (world.getCurrentWorldData().captureBlockStates) return; // CraftBukkit // Folia - region threading
         if (!world.isClientSide) {
             BlockState iblockdata = blockEntity.getBlockState();
             boolean flag = iblockdata.is(Blocks.WITHER_SKELETON_SKULL) || iblockdata.is(Blocks.WITHER_SKELETON_WALL_SKULL);
diff --git a/src/main/java/net/minecraft/world/level/block/entity/BeaconBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/BeaconBlockEntity.java
index 4b81b0180dfc96fc6a88646838a886ca5b5d301b..d973ac7d15ee087deb6c6c55a5d10beeedcca8e0 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/BeaconBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/BeaconBlockEntity.java
@@ -211,7 +211,7 @@ public class BeaconBlockEntity extends BlockEntity implements MenuProvider, Name
         }
 
         i1 = blockEntity.levels;
-        if (world.getGameTime() % 80L == 0L) {
+        if (world.getRedstoneGameTime() % 80L == 0L) { // Folia - region threading
             if (!blockEntity.beamSections.isEmpty()) {
                 blockEntity.levels = BeaconBlockEntity.updateBase(world, i, j, k);
             }
diff --git a/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
index 9ea74d37cd951e0dc76d20ed8234b5871035566c..5be70de980d8b475d64dfbb029d11ba30894b880 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/BlockEntity.java
@@ -26,7 +26,7 @@ import co.aikar.timings.MinecraftTimings; // Paper
 import co.aikar.timings.Timing; // Paper
 
 public abstract class BlockEntity {
-    static boolean ignoreTileUpdates; // Paper - Perf: Optimize Hoppers
+    static final ThreadLocal<Boolean> IGNORE_TILE_UPDATES = ThreadLocal.withInitial(() -> Boolean.FALSE); // Paper - Perf: Optimize Hoppers // Folia - region threading
 
     public Timing tickTimer = MinecraftTimings.getTileEntityTimings(this); // Paper
     // CraftBukkit start - data containers
@@ -41,6 +41,12 @@ public abstract class BlockEntity {
     protected boolean remove;
     private BlockState blockState;
 
+    // Folia start - region ticking
+    public void updateTicks(final long fromTickOffset, final long fromRedstoneTimeOffset) {
+
+    }
+    // Folia end - region ticking
+
     public BlockEntity(BlockEntityType<?> type, BlockPos pos, BlockState state) {
         this.type = type;
         this.worldPosition = pos.immutable();
@@ -162,7 +168,7 @@ public abstract class BlockEntity {
 
     public void setChanged() {
         if (this.level != null) {
-            if (ignoreTileUpdates) return; // Paper - Perf: Optimize Hoppers
+            if (IGNORE_TILE_UPDATES.get().booleanValue()) return; // Paper - Perf: Optimize Hoppers // Folia - region threading
             BlockEntity.setChanged(this.level, this.worldPosition, this.blockState);
         }
 
diff --git a/src/main/java/net/minecraft/world/level/block/entity/BrewingStandBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/BrewingStandBlockEntity.java
index 9bb542ce3a8c52e1688bb1f66fc916dd23a5fd10..23ebbc58f8f7eeb6398d21b3e96772971d02bcac 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/BrewingStandBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/BrewingStandBlockEntity.java
@@ -56,7 +56,7 @@ public class BrewingStandBlockEntity extends BaseContainerBlockEntity implements
     public int fuel;
     protected final ContainerData dataAccess;
     // CraftBukkit start - add fields and methods
-    private int lastTick = MinecraftServer.currentTick;
+    //private int lastTick = MinecraftServer.currentTick; // Folia - region ticking - restore original timers
     public List<HumanEntity> transaction = new java.util.ArrayList<HumanEntity>();
     private int maxStack = MAX_STACK;
 
@@ -173,11 +173,10 @@ public class BrewingStandBlockEntity extends BaseContainerBlockEntity implements
         ItemStack itemstack1 = (ItemStack) blockEntity.items.get(3);
 
         // CraftBukkit start - Use wall time instead of ticks for brewing
-        int elapsedTicks = MinecraftServer.currentTick - blockEntity.lastTick;
-        blockEntity.lastTick = MinecraftServer.currentTick;
+        // Folia - region ticking - restore original timers
 
         if (flag1) {
-            blockEntity.brewTime -= elapsedTicks;
+            --blockEntity.brewTime; // Folia - region ticking - restore original timers
             boolean flag2 = blockEntity.brewTime <= 0; // == -> <=
             // CraftBukkit end
 
diff --git a/src/main/java/net/minecraft/world/level/block/entity/CommandBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/CommandBlockEntity.java
index f08c77e20462bada221b5ed395ceb2f7d39ee7c0..8422e4fb36342555937002afcb3611d604a60c07 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/CommandBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/CommandBlockEntity.java
@@ -57,6 +57,13 @@ public class CommandBlockEntity extends BlockEntity {
             return new CommandSourceStack(this, Vec3.atCenterOf(CommandBlockEntity.this.worldPosition), new Vec2(0.0F, enumdirection.toYRot()), this.getLevel(), this.getLevel().paperConfig().commandBlocks.permissionsLevel, this.getName().getString(), this.getName(), this.getLevel().getServer(), (Entity) null); // Paper - configurable command block perm level
         }
 
+        // Folia start
+        @Override
+        public void threadCheck() {
+            io.papermc.paper.util.TickThread.ensureTickThread((ServerLevel) CommandBlockEntity.this.level, CommandBlockEntity.this.worldPosition, "Asynchronous sendSystemMessage to a command block");
+        }
+        // Folia end
+
         @Override
         public boolean isValid() {
             return !CommandBlockEntity.this.isRemoved();
diff --git a/src/main/java/net/minecraft/world/level/block/entity/ConduitBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/ConduitBlockEntity.java
index 37e0b762b86e74f607a4541ecb7b24ad7a591d0e..4ddc3b3dc704610bf1fb7082e1c89a284c245fce 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/ConduitBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/ConduitBlockEntity.java
@@ -83,7 +83,7 @@ public class ConduitBlockEntity extends BlockEntity {
 
     public static void clientTick(Level world, BlockPos pos, BlockState state, ConduitBlockEntity blockEntity) {
         ++blockEntity.tickCount;
-        long i = world.getGameTime();
+        long i = world.getRedstoneGameTime(); // Folia - region threading
         List<BlockPos> list = blockEntity.effectBlocks;
 
         if (i % 40L == 0L) {
@@ -101,7 +101,7 @@ public class ConduitBlockEntity extends BlockEntity {
 
     public static void serverTick(Level world, BlockPos pos, BlockState state, ConduitBlockEntity blockEntity) {
         ++blockEntity.tickCount;
-        long i = world.getGameTime();
+        long i = world.getRedstoneGameTime(); // Folia - region threading
         List<BlockPos> list = blockEntity.effectBlocks;
 
         if (i % 40L == 0L) {
diff --git a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
index cdb739df2a285032d25d84f4464f202a7a3fa578..82e7e76fecceb55522b5828a56f036e42ef55201 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/HopperBlockEntity.java
@@ -50,7 +50,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     public static final int HOPPER_CONTAINER_SIZE = 5;
     private NonNullList<ItemStack> items;
     public int cooldownTime;
-    private long tickedGameTime;
+    private long tickedGameTime = Long.MIN_VALUE; // Folia - region threading
 
     // CraftBukkit start - add fields and methods
     public List<HumanEntity> transaction = new java.util.ArrayList<HumanEntity>();
@@ -82,6 +82,16 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
     // CraftBukkit end
 
+    // Folia start - region threading
+    @Override
+    public void updateTicks(final long fromTickOffset, final long fromRedstoneTimeOffset) {
+        super.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+        if (this.tickedGameTime != Long.MIN_VALUE) {
+            this.tickedGameTime += fromRedstoneTimeOffset;
+        }
+    }
+    // Folia end - region threading
+
     public HopperBlockEntity(BlockPos pos, BlockState state) {
         super(BlockEntityType.HOPPER, pos, state);
         this.items = NonNullList.withSize(5, ItemStack.EMPTY);
@@ -137,7 +147,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
     public static void pushItemsTick(Level world, BlockPos pos, BlockState state, HopperBlockEntity blockEntity) {
         --blockEntity.cooldownTime;
-        blockEntity.tickedGameTime = world.getGameTime();
+        blockEntity.tickedGameTime = world.getRedstoneGameTime(); // Folia - region threading
         if (!blockEntity.isOnCooldown()) {
             blockEntity.setCooldown(0);
             // Spigot start
@@ -234,12 +244,11 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     // Paper start - Perf: Optimize Hoppers
-    private static boolean skipPullModeEventFire;
-    private static boolean skipPushModeEventFire;
-    public static boolean skipHopperEvents;
+    // Folia - region threading - moved to RegionizedWorldData
 
     private static boolean hopperPush(final Level level, final Container destination, final Direction direction, final HopperBlockEntity hopper) {
-        skipPushModeEventFire = skipHopperEvents;
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = level.getCurrentWorldData(); // Folia - region threading
+        worldData.skipPushModeEventFire = worldData.skipHopperEvents; // Folia - region threading
         boolean foundItem = false;
         for (int i = 0; i < hopper.getContainerSize(); ++i) {
             final ItemStack item = hopper.getItem(i);
@@ -254,7 +263,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
                 // We only need to fire the event once to give protection plugins a chance to cancel this event
                 // Because nothing uses getItem, every event call should end up the same result.
-                if (!skipPushModeEventFire) {
+                if (!worldData.skipPushModeEventFire) { // Folia - region threading
                     movedItem = callPushMoveEvent(destination, movedItem, hopper);
                     if (movedItem == null) { // cancelled
                         origItemStack.setCount(originalItemCount);
@@ -284,13 +293,14 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     private static boolean hopperPull(final Level level, final Hopper hopper, final Container container, ItemStack origItemStack, final int i) {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = level.getCurrentWorldData(); // Folia - region threading
         ItemStack movedItem = origItemStack;
         final int originalItemCount = origItemStack.getCount();
         final int movedItemCount = Math.min(level.spigotConfig.hopperAmount, originalItemCount);
         container.setChanged(); // original logic always marks source inv as changed even if no move happens.
         movedItem.setCount(movedItemCount);
 
-        if (!skipPullModeEventFire) {
+        if (!worldData.skipPullModeEventFire) { // Folia - region threading
             movedItem = callPullMoveEvent(hopper, container, movedItem);
             if (movedItem == null) { // cancelled
                 origItemStack.setCount(originalItemCount);
@@ -310,9 +320,9 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
                 origItemStack.setCount(originalItemCount - movedItemCount + remainingItemCount);
             }
 
-            ignoreTileUpdates = true;
+            IGNORE_TILE_UPDATES.set(true); // Folia - region threading
             container.setItem(i, origItemStack);
-            ignoreTileUpdates = false;
+            IGNORE_TILE_UPDATES.set(false); // Folia - region threading
             container.setChanged();
             return true;
         }
@@ -327,12 +337,13 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
     @Nullable
     private static ItemStack callPushMoveEvent(Container iinventory, ItemStack itemstack, HopperBlockEntity hopper) {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData(); // Folia - region threading
         final Inventory destinationInventory = getInventory(iinventory);
         final io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent event = new io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent(hopper.getOwner(false).getInventory(),
             CraftItemStack.asCraftMirror(itemstack), destinationInventory, true);
         final boolean result = event.callEvent();
         if (!event.calledGetItem && !event.calledSetItem) {
-            skipPushModeEventFire = true;
+            worldData.skipPushModeEventFire = true; // Folia - region threading
         }
         if (!result) {
             cooldownHopper(hopper);
@@ -348,6 +359,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
 
     @Nullable
     private static ItemStack callPullMoveEvent(final Hopper hopper, final Container container, final ItemStack itemstack) {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData(); // Folia - region threading
         final Inventory sourceInventory = getInventory(container);
         final Inventory destination = getInventory(hopper);
 
@@ -355,7 +367,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
         final io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent event = new io.papermc.paper.event.inventory.PaperInventoryMoveItemEvent(sourceInventory, CraftItemStack.asCraftMirror(itemstack), destination, false);
         final boolean result = event.callEvent();
         if (!event.calledGetItem && !event.calledSetItem) {
-            skipPullModeEventFire = true;
+            worldData.skipPullModeEventFire = true; // Folia - region threading
         }
         if (!result) {
             cooldownHopper(hopper);
@@ -518,13 +530,14 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     public static boolean suckInItems(Level world, Hopper hopper) {
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionizedWorldData(); // Folia - region threading
         Container iinventory = HopperBlockEntity.getSourceContainer(world, hopper);
 
         if (iinventory != null) {
             Direction enumdirection = Direction.DOWN;
 
             // Paper start - Perf: Optimize Hoppers
-            skipPullModeEventFire = skipHopperEvents;
+            worldData.skipPullModeEventFire = worldData.skipHopperEvents; // Folia - region threading
             // merge container isEmpty check and move logic into one loop
             if (iinventory instanceof WorldlyContainer worldlyContainer) {
                 for (final int slot : worldlyContainer.getSlotsForFace(enumdirection)) {
@@ -724,9 +737,9 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
                     stack = stack.split(to.getMaxStackSize());
                 }
                 // Spigot end
-                ignoreTileUpdates = true; // Paper - Perf: Optimize Hoppers
+                IGNORE_TILE_UPDATES.set(Boolean.TRUE); // Paper - Perf: Optimize Hoppers // Folia - region threading
                 to.setItem(slot, stack);
-                ignoreTileUpdates = false; // Paper - Perf: Optimize Hoppers
+                IGNORE_TILE_UPDATES.set(Boolean.FALSE); // Paper - Perf: Optimize Hoppers // Folia - region threading
                 stack = leftover; // Paper - Make hoppers respect inventory max stack size
                 flag = true;
             } else if (HopperBlockEntity.canMergeItems(itemstack1, stack)) {
diff --git a/src/main/java/net/minecraft/world/level/block/entity/SculkCatalystBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/SculkCatalystBlockEntity.java
index 83481539e058e5f428d9951e409fed62ef159e5c..48260dce982181e2ee4e92614f8ed3af4bf83af0 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/SculkCatalystBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/SculkCatalystBlockEntity.java
@@ -43,9 +43,9 @@ public class SculkCatalystBlockEntity extends BlockEntity implements GameEventLi
     // Paper end - Fix NPE in SculkBloomEvent world access
 
     public static void serverTick(Level world, BlockPos pos, BlockState state, SculkCatalystBlockEntity blockEntity) {
-        org.bukkit.craftbukkit.event.CraftEventFactory.sourceBlockOverride = blockEntity.getBlockPos(); // CraftBukkit - SPIGOT-7068: Add source block override, not the most elegant way but better than passing down a BlockPosition up to five methods deep.
+        org.bukkit.craftbukkit.event.CraftEventFactory.sourceBlockOverrideRT.set(blockEntity.getBlockPos()); // CraftBukkit - SPIGOT-7068: Add source block override, not the most elegant way but better than passing down a BlockPosition up to five methods deep. // Folia - region threading
         blockEntity.catalystListener.getSculkSpreader().updateCursors(world, pos, world.getRandom(), true);
-        org.bukkit.craftbukkit.event.CraftEventFactory.sourceBlockOverride = null; // CraftBukkit
+        org.bukkit.craftbukkit.event.CraftEventFactory.sourceBlockOverrideRT.set(null); // CraftBukkit // Folia - region threading
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/world/level/block/entity/TheEndGatewayBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/TheEndGatewayBlockEntity.java
index 098fde8200a11f91f934ddab6b1486dac4014dfe..412fa8a03be7215fa2695f07ac4f2334d1e70903 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/TheEndGatewayBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/TheEndGatewayBlockEntity.java
@@ -51,9 +51,12 @@ public class TheEndGatewayBlockEntity extends TheEndPortalBlockEntity {
     public long age;
     private int teleportCooldown;
     @Nullable
-    public BlockPos exitPortal;
+    public volatile BlockPos exitPortal; // Folia - region threading - volatile
     public boolean exactTeleport;
 
+    private static final java.util.concurrent.atomic.AtomicLong SEARCHING_FOR_EXIT_ID_GENERATOR = new java.util.concurrent.atomic.AtomicLong(); // Folia - region threading
+    private Long searchingForExitId; // Folia - region threading
+
     public TheEndGatewayBlockEntity(BlockPos pos, BlockState state) {
         super(BlockEntityType.END_GATEWAY, pos, state);
     }
@@ -121,7 +124,7 @@ public class TheEndGatewayBlockEntity extends TheEndPortalBlockEntity {
     }
 
     public static boolean canEntityTeleport(Entity entity) {
-        return EntitySelector.NO_SPECTATORS.test(entity) && !entity.getRootVehicle().isOnPortalCooldown();
+        return EntitySelector.NO_SPECTATORS.test(entity) && !entity.getRootVehicle().isOnPortalCooldown() && entity.canPortalAsync(true); // Folia - region threading - correct portal check
     }
 
     public boolean isSpawning() {
@@ -169,8 +172,136 @@ public class TheEndGatewayBlockEntity extends TheEndPortalBlockEntity {
         }
     }
 
+    // Folia start - region threading
+    private void trySearchForExit(ServerLevel world, BlockPos fromPos) {
+        if (this.searchingForExitId != null) {
+            return;
+        }
+        this.searchingForExitId = Long.valueOf(SEARCHING_FOR_EXIT_ID_GENERATOR.getAndIncrement());
+        int chunkX = fromPos.getX() >> 4;
+        int chunkZ = fromPos.getZ() >> 4;
+        world.chunkTaskScheduler.chunkHolderManager.addTicketAtLevel(
+            net.minecraft.server.level.TicketType.END_GATEWAY_EXIT_SEARCH,
+            chunkX, chunkZ,
+            io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.BLOCK_TICKING_TICKET_LEVEL,
+            this.searchingForExitId
+        );
+
+        ca.spottedleaf.concurrentutil.completable.Completable<BlockPos> complete = new ca.spottedleaf.concurrentutil.completable.Completable<>();
+
+        complete.addWaiter((tpLoc, throwable) -> {
+            // create the exit portal
+            TheEndGatewayBlockEntity.LOGGER.debug("Creating portal at {}", tpLoc);
+            TheEndGatewayBlockEntity.spawnGatewayPortal(world, tpLoc, EndGatewayConfiguration.knownExit(fromPos, false));
+
+            // need to go onto the tick thread to avoid saving issues
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                world, chunkX, chunkZ,
+                () -> {
+                    // update the exit portal location
+                    TheEndGatewayBlockEntity.this.exitPortal = tpLoc;
+
+                    // remove ticket keeping the gateway loaded
+                    world.chunkTaskScheduler.chunkHolderManager.removeTicketAtLevel(
+                        net.minecraft.server.level.TicketType.END_GATEWAY_EXIT_SEARCH,
+                        chunkX, chunkZ,
+                        io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.BLOCK_TICKING_TICKET_LEVEL,
+                        this.searchingForExitId
+                    );
+                    TheEndGatewayBlockEntity.this.searchingForExitId = null;
+                }
+            );
+        });
+
+        findOrCreateValidTeleportPosRegionThreading(world, fromPos, complete);
+    }
+
+    private static void teleportRegionThreading(Level world, BlockPos pos, BlockState state, Entity entity, TheEndGatewayBlockEntity blockEntity) {
+        // can we even teleport in this dimension?
+        if (blockEntity.exitPortal == null && world.getTypeKey() != LevelStem.END) {
+            return;
+        }
+
+        ServerLevel serverWorld = (ServerLevel)world;
+
+        // First, find the position we are trying to teleport to
+        BlockPos teleportPos = blockEntity.exitPortal;
+        boolean isExactTeleport = blockEntity.exactTeleport;
+
+        if (teleportPos == null) {
+            blockEntity.trySearchForExit(serverWorld, pos);
+            return;
+        }
+
+        Entity chosenEntity;
+        if (entity instanceof ThrownEnderpearl pearl) {
+            Entity owner = pearl.getOwner();
+
+            if (owner instanceof ServerPlayer player) {
+                CriteriaTriggers.ENTER_BLOCK.trigger(player, state);
+            }
+
+            if (owner != null) {
+                // vanilla behavior is to just break if the owner is riding anything
+                // it's not likely intentional that throwing a pearl while riding something is intended
+                // to teleport the vehicle, rather just the owner given the lack of getRootVehicle
+                owner.unRide();
+                chosenEntity = owner;
+                pearl.discard(EntityRemoveEvent.Cause.HIT);
+            } else {
+                // see above for unRide()
+                pearl.unRide();
+                chosenEntity = pearl;
+            }
+        } else {
+            chosenEntity = entity.getRootVehicle();
+        }
+
+        // This needs to be first, as we are only guaranteed to be on the corresponding region tick thread here
+        TheEndGatewayBlockEntity.triggerCooldown(world, pos, state, blockEntity);
+
+        if (isExactTeleport) {
+            // blind teleport
+            chosenEntity.teleportAsync(
+                serverWorld, Vec3.atCenterOf(teleportPos), null, null, null,
+                PlayerTeleportEvent.TeleportCause.END_GATEWAY, Entity.TELEPORT_FLAG_LOAD_CHUNK | Entity.TELEPORT_FLAG_TELEPORT_PASSENGERS,
+                (Entity teleportedEntity) -> {
+                    for (Entity passenger : teleportedEntity.getSelfAndPassengers().toList()) {
+                        passenger.setPortalCooldown();
+                    }
+                }
+            );
+        } else {
+            // we could hack around by first loading the chunks, then calling back to here and checking if the entity
+            // should be teleported, something something else...
+            // however, we know the target location cannot differ by one region section: so we can
+            // just teleport and adjust the position after
+            chosenEntity.teleportAsync(
+                serverWorld, Vec3.atCenterOf(teleportPos), null, null, null,
+                PlayerTeleportEvent.TeleportCause.END_GATEWAY, Entity.TELEPORT_FLAG_LOAD_CHUNK | Entity.TELEPORT_FLAG_TELEPORT_PASSENGERS,
+                (Entity teleportedEntity) -> {
+                    for (Entity passenger : teleportedEntity.getSelfAndPassengers().toList()) {
+                        passenger.setPortalCooldown();
+                    }
+
+                    // adjust to the final exit position
+                    Vec3 adjusted = Vec3.atCenterOf(TheEndGatewayBlockEntity.findExitPosition(serverWorld, teleportPos));
+                    // teleportTo will adjust rider positions
+                    teleportedEntity.teleportTo(adjusted.x, adjusted.y, adjusted.z);
+                }
+            );
+        }
+    }
+    // Folia end - region threading
+
     public static void teleportEntity(Level world, BlockPos pos, BlockState state, Entity entity, TheEndGatewayBlockEntity blockEntity) {
         if (world instanceof ServerLevel && !blockEntity.isCoolingDown()) {
+            // Folia start - region threading
+            if (true) {
+                teleportRegionThreading(world, pos, state, entity, blockEntity);
+                return;
+            }
+            // Folia end - region threading
             ServerLevel worldserver = (ServerLevel) world;
 
             blockEntity.teleportCooldown = 100;
@@ -275,6 +406,129 @@ public class TheEndGatewayBlockEntity extends TheEndPortalBlockEntity {
         return TheEndGatewayBlockEntity.findTallestBlock(world, blockposition1, 16, true);
     }
 
+    // Folia start - region threading
+    private static void findOrCreateValidTeleportPosRegionThreading(ServerLevel world, BlockPos pos,
+                                                                    ca.spottedleaf.concurrentutil.completable.Completable<BlockPos> complete) {
+        ca.spottedleaf.concurrentutil.completable.Completable<Vec3> tentativeSelection = new ca.spottedleaf.concurrentutil.completable.Completable<>();
+
+        tentativeSelection.addWaiter((vec3d, throwable) -> {
+            LevelChunk chunk = TheEndGatewayBlockEntity.getChunk(world, vec3d);
+            BlockPos blockposition1 = TheEndGatewayBlockEntity.findValidSpawnInChunk(chunk);
+            if (blockposition1 == null) {
+                BlockPos blockposition2 = new BlockPos(
+                    io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(vec3d.x + 0.5D),
+                    io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(75.0D),
+                    io.papermc.paper.util.CoordinateUtils.getBlockCoordinate(vec3d.z + 0.5D)
+                );
+
+                TheEndGatewayBlockEntity.LOGGER.debug("Failed to find a suitable block to teleport to, spawning an island on {}", blockposition2);
+                world.registryAccess().registry(Registries.CONFIGURED_FEATURE).flatMap((iregistry) -> {
+                    return iregistry.getHolder(EndFeatures.END_ISLAND);
+                }).ifPresent((holder_c) -> {
+                    ((ConfiguredFeature) holder_c.value()).place(world, world.getChunkSource().getGenerator(), RandomSource.create(blockposition2.asLong()), blockposition2);
+                });
+                blockposition1 = blockposition2;
+            } else {
+                TheEndGatewayBlockEntity.LOGGER.debug("Found suitable block to teleport to: {}", blockposition1);
+            }
+
+            // Here, there is no guarantee the chunks in 1 radius are in this region due to the fact that we just chained
+            // possibly 16x chunk loads along an axis (findExitPortalXZPosTentativeRegionThreading) using the chunk queue
+            // (regioniser only guarantees at least 8 chunks along a single axis)
+            // so, we need to schedule for the next tick
+            int posX = blockposition1.getX();
+            int posZ = blockposition1.getZ();
+            int radius = 16;
+
+            BlockPos finalBlockPosition1 = blockposition1;
+            world.loadChunksAsync(blockposition1, radius,
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+                (List<net.minecraft.world.level.chunk.ChunkAccess> chunks) -> {
+                    // make sure chunks are kept loaded
+                    for (net.minecraft.world.level.chunk.ChunkAccess access : chunks) {
+                        world.chunkSource.addTicketAtLevel(
+                            net.minecraft.server.level.TicketType.DELAYED, access.getPos(),
+                            io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.FULL_LOADED_TICKET_LEVEL,
+                            net.minecraft.util.Unit.INSTANCE
+                        );
+                    }
+                    // now after the chunks are loaded, we can delay by one tick
+                    io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(
+                        world, posX >> 4, posZ >> 4, () -> {
+                            // find final location
+                            BlockPos tpLoc = TheEndGatewayBlockEntity.findTallestBlock(world, finalBlockPosition1, radius, true);
+
+                            // done
+                            complete.complete(tpLoc.above(10));
+                        }
+                    );
+                }
+            );
+        });
+
+        // fire off chain
+        findExitPortalXZPosTentativeRegionThreading(world, pos, tentativeSelection);
+    }
+
+    private static void findExitPortalXZPosTentativeRegionThreading(ServerLevel world, BlockPos pos,
+                                                                    ca.spottedleaf.concurrentutil.completable.Completable<Vec3> complete) {
+        Vec3 posDirFromOrigin = new Vec3(pos.getX(), 0.0D, pos.getZ()).normalize();
+        Vec3 posDirExtruded = posDirFromOrigin.scale(1024.0D);
+
+        class Vars {
+            int i = 16;
+            boolean mode = false;
+            Vec3 currPos = posDirExtruded;
+        }
+        Vars vars = new Vars();
+
+        Runnable handle = new Runnable() {
+            @Override
+            public void run() {
+                if (vars.mode != TheEndGatewayBlockEntity.isChunkEmpty(world, vars.currPos)) {
+                    vars.i = 0; // fall back to completing
+                }
+
+                // try to load next chunk
+                if (vars.i-- <= 0) {
+                    if (vars.mode) {
+                        complete.complete(vars.currPos);
+                        return;
+                    }
+                    vars.mode = true;
+                    vars.i = 16;
+                }
+
+                vars.currPos = vars.currPos.add(posDirFromOrigin.scale(vars.mode ? 16.0 : -16.0));
+                // schedule next iteration
+                Runnable handleButInitialised = this;
+                world.chunkTaskScheduler.scheduleChunkLoad(
+                    io.papermc.paper.util.CoordinateUtils.getChunkX(vars.currPos),
+                    io.papermc.paper.util.CoordinateUtils.getChunkZ(vars.currPos),
+                    net.minecraft.world.level.chunk.ChunkStatus.FULL,
+                    true,
+                    ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+                    (chunk) -> {
+                        handleButInitialised.run();
+                    }
+                );
+            }
+        };
+
+        // kick off first chunk load
+        world.chunkTaskScheduler.scheduleChunkLoad(
+            io.papermc.paper.util.CoordinateUtils.getChunkX(posDirExtruded),
+            io.papermc.paper.util.CoordinateUtils.getChunkZ(posDirExtruded),
+            net.minecraft.world.level.chunk.ChunkStatus.FULL,
+            true,
+            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+            (chunk) -> {
+                handle.run();
+            }
+        );
+    }
+    // Folia end - region threading
+
     private static Vec3 findExitPortalXZPosTentative(ServerLevel world, BlockPos pos) {
         Vec3 vec3d = (new Vec3((double) pos.getX(), 0.0D, (double) pos.getZ())).normalize();
         boolean flag = true;
diff --git a/src/main/java/net/minecraft/world/level/block/entity/TickingBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/TickingBlockEntity.java
index 28e3b73507b988f7234cbf29c4024c88180d0aef..c8facee29ee08e0975528083f89b64f0b593957f 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/TickingBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/TickingBlockEntity.java
@@ -10,4 +10,6 @@ public interface TickingBlockEntity {
     BlockPos getPos();
 
     String getType();
+
+    BlockEntity getTileEntity(); // Folia - region threading
 }
diff --git a/src/main/java/net/minecraft/world/level/block/grower/TreeGrower.java b/src/main/java/net/minecraft/world/level/block/grower/TreeGrower.java
index 8cb822fed0cda4268f288feae1079a3dc4dc103e..3f53d51960ded5df3b8be12362110f22b3c495b8 100644
--- a/src/main/java/net/minecraft/world/level/block/grower/TreeGrower.java
+++ b/src/main/java/net/minecraft/world/level/block/grower/TreeGrower.java
@@ -175,51 +175,53 @@ public final class TreeGrower {
     // CraftBukkit start
     private void setTreeType(Holder<ConfiguredFeature<?, ?>> holder) {
         ResourceKey<ConfiguredFeature<?, ?>> worldgentreeabstract = holder.unwrapKey().get();
+        TreeType treeType; // Folia - region threading
         if (worldgentreeabstract == TreeFeatures.OAK || worldgentreeabstract == TreeFeatures.OAK_BEES_005) {
-            SaplingBlock.treeType = TreeType.TREE;
+            treeType = TreeType.TREE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.HUGE_RED_MUSHROOM) {
-            SaplingBlock.treeType = TreeType.RED_MUSHROOM;
+            treeType = TreeType.RED_MUSHROOM; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.HUGE_BROWN_MUSHROOM) {
-            SaplingBlock.treeType = TreeType.BROWN_MUSHROOM;
+            treeType = TreeType.BROWN_MUSHROOM; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.JUNGLE_TREE) {
-            SaplingBlock.treeType = TreeType.COCOA_TREE;
+            treeType = TreeType.COCOA_TREE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.JUNGLE_TREE_NO_VINE) {
-            SaplingBlock.treeType = TreeType.SMALL_JUNGLE;
+            treeType = TreeType.SMALL_JUNGLE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.PINE) {
-            SaplingBlock.treeType = TreeType.TALL_REDWOOD;
+            treeType = TreeType.TALL_REDWOOD; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.SPRUCE) {
-            SaplingBlock.treeType = TreeType.REDWOOD;
+            treeType = TreeType.REDWOOD; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.ACACIA) {
-            SaplingBlock.treeType = TreeType.ACACIA;
+            treeType = TreeType.ACACIA; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.BIRCH || worldgentreeabstract == TreeFeatures.BIRCH_BEES_005) {
-            SaplingBlock.treeType = TreeType.BIRCH;
+            treeType = TreeType.BIRCH; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.SUPER_BIRCH_BEES_0002) {
-            SaplingBlock.treeType = TreeType.TALL_BIRCH;
+            treeType = TreeType.TALL_BIRCH; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.SWAMP_OAK) {
-            SaplingBlock.treeType = TreeType.SWAMP;
+            treeType = TreeType.SWAMP; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.FANCY_OAK || worldgentreeabstract == TreeFeatures.FANCY_OAK_BEES_005) {
-            SaplingBlock.treeType = TreeType.BIG_TREE;
+            treeType = TreeType.BIG_TREE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.JUNGLE_BUSH) {
-            SaplingBlock.treeType = TreeType.JUNGLE_BUSH;
+            treeType = TreeType.JUNGLE_BUSH; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.DARK_OAK) {
-            SaplingBlock.treeType = TreeType.DARK_OAK;
+            treeType = TreeType.DARK_OAK; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.MEGA_SPRUCE) {
-            SaplingBlock.treeType = TreeType.MEGA_REDWOOD;
+            treeType = TreeType.MEGA_REDWOOD; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.MEGA_PINE) {
-            SaplingBlock.treeType = TreeType.MEGA_REDWOOD;
+            treeType = TreeType.MEGA_REDWOOD; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.MEGA_JUNGLE_TREE) {
-            SaplingBlock.treeType = TreeType.JUNGLE;
+            treeType = TreeType.JUNGLE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.AZALEA_TREE) {
-            SaplingBlock.treeType = TreeType.AZALEA;
+            treeType = TreeType.AZALEA; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.MANGROVE) {
-            SaplingBlock.treeType = TreeType.MANGROVE;
+            treeType = TreeType.MANGROVE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.TALL_MANGROVE) {
-            SaplingBlock.treeType = TreeType.TALL_MANGROVE;
+            treeType = TreeType.TALL_MANGROVE; // Folia - region threading
         } else if (worldgentreeabstract == TreeFeatures.CHERRY || worldgentreeabstract == TreeFeatures.CHERRY_BEES_005) {
-            SaplingBlock.treeType = TreeType.CHERRY;
+            treeType = TreeType.CHERRY; // Folia - region threading
         } else {
             throw new IllegalArgumentException("Unknown tree generator " + worldgentreeabstract);
         }
+        SaplingBlock.treeTypeRT.set(treeType); // Folia - region threading
     }
     // CraftBukkit end
 
diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
index be74adc86f0ca467f3b59e7b57fd47a8f381d86e..363a712d6b9e717b075aa52643c6cf91497e7c3b 100644
--- a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
@@ -152,7 +152,7 @@ public class PistonBaseBlock extends DirectionalBlock {
                 if (tileentity instanceof PistonMovingBlockEntity) {
                     PistonMovingBlockEntity tileentitypiston = (PistonMovingBlockEntity) tileentity;
 
-                    if (tileentitypiston.isExtending() && (tileentitypiston.getProgress(0.0F) < 0.5F || world.getGameTime() == tileentitypiston.getLastTicked() || ((ServerLevel) world).isHandlingTick())) {
+                    if (tileentitypiston.isExtending() && (tileentitypiston.getProgress(0.0F) < 0.5F || world.getRedstoneGameTime() == tileentitypiston.getLastTicked() || ((ServerLevel) world).isHandlingTick())) { // Folia - region threading
                         b0 = 2;
                     }
                 }
diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
index 9f45dda6ff45ac1ffb7ac99575b7d09bdc61c56a..9a0d66b48470a6bef70b6643ff05812da519adfa 100644
--- a/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
@@ -39,9 +39,19 @@ public class PistonMovingBlockEntity extends BlockEntity {
     private static final ThreadLocal<Direction> NOCLIP = ThreadLocal.withInitial(() -> null);
     private float progress;
     private float progressO;
-    private long lastTicked;
+    private long lastTicked = Long.MIN_VALUE; // Folia - region threading
     private int deathTicks;
 
+    // Folia start - region threading
+    @Override
+    public void updateTicks(long fromTickOffset, long fromRedstoneTimeOffset) {
+        super.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+        if (this.lastTicked != Long.MIN_VALUE) {
+            this.lastTicked += fromRedstoneTimeOffset;
+        }
+    }
+    // Folia end - region threading
+
     public PistonMovingBlockEntity(BlockPos pos, BlockState state) {
         super(BlockEntityType.PISTON, pos, state);
     }
@@ -148,8 +158,8 @@ public class PistonMovingBlockEntity extends BlockEntity {
 
                                 entity.setDeltaMovement(e, g, h);
                                 // Paper - EAR items stuck in in slime pushed by a piston
-                                entity.activatedTick = Math.max(entity.activatedTick, net.minecraft.server.MinecraftServer.currentTick + 10);
-                                entity.activatedImmunityTick = Math.max(entity.activatedImmunityTick, net.minecraft.server.MinecraftServer.currentTick + 10);
+                                entity.activatedTick = Math.max(entity.activatedTick, io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + 10); // Folia - region threading
+                                entity.activatedImmunityTick = Math.max(entity.activatedImmunityTick, io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + 10); // Folia - region threading
                                 // Paper end
                                 break;
                             }
@@ -289,7 +299,7 @@ public class PistonMovingBlockEntity extends BlockEntity {
     }
 
     public static void tick(Level world, BlockPos pos, BlockState state, PistonMovingBlockEntity blockEntity) {
-        blockEntity.lastTicked = world.getGameTime();
+        blockEntity.lastTicked = world.getRedstoneGameTime(); // Folia - region threading
         blockEntity.progressO = blockEntity.progress;
         if (blockEntity.progressO >= 1.0F) {
             if (world.isClientSide && blockEntity.deathTicks < 5) {
diff --git a/src/main/java/net/minecraft/world/level/border/WorldBorder.java b/src/main/java/net/minecraft/world/level/border/WorldBorder.java
index 350aabd20329f429248c84d73ab8b5eb145943a7..bdb864f5e7a1bacde88be632442c9de000ce7729 100644
--- a/src/main/java/net/minecraft/world/level/border/WorldBorder.java
+++ b/src/main/java/net/minecraft/world/level/border/WorldBorder.java
@@ -33,19 +33,19 @@ public class WorldBorder {
 
     public WorldBorder() {}
 
+    // Folia - region threading - TODO make this shit thread-safe
+
     public boolean isWithinBounds(BlockPos pos) {
         return (double) (pos.getX() + 1) > this.getMinX() && (double) pos.getX() < this.getMaxX() && (double) (pos.getZ() + 1) > this.getMinZ() && (double) pos.getZ() < this.getMaxZ();
     }
 
     // Paper start - Bound treasure maps to world border
-    private final BlockPos.MutableBlockPos mutPos = new BlockPos.MutableBlockPos();
+    private static final ThreadLocal<BlockPos.MutableBlockPos> mutPos = ThreadLocal.withInitial(() -> new BlockPos.MutableBlockPos()); // Folia - region threading
     public boolean isBlockInBounds(int chunkX, int chunkZ) {
-        this.mutPos.set(chunkX, 64, chunkZ);
-        return this.isWithinBounds(this.mutPos);
+        return this.isWithinBounds(mutPos.get().set(chunkX, 64, chunkZ)); // Folia - region threading
     }
     public boolean isChunkInBounds(int chunkX, int chunkZ) {
-        this.mutPos.set(((chunkX << 4) + 15), 64, (chunkZ << 4) + 15);
-        return this.isWithinBounds(this.mutPos);
+        return this.isWithinBounds(mutPos.get().set(((chunkX << 4) + 15), 64, (chunkZ << 4) + 15)); // Folia - region threading
     }
     // Paper end - Bound treasure maps to world border
 
diff --git a/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java b/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
index 4c03297fb523ef59cd9d11edbed437398e562a00..484cd058ca3cd317d2c82e502c064edca4293e74 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
@@ -320,7 +320,7 @@ public abstract class ChunkGenerator {
     }
 
     private static boolean tryAddReference(StructureManager structureAccessor, StructureStart start) {
-        if (start.canBeReferenced()) {
+        if (start.tryReference()) { // Folia - region threading
             structureAccessor.addReference(start);
             return true;
         } else {
diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
index 465458e8a7dbaf9afb32709a71c7b2620d1e1fd2..ff1a7b78fa010857daab7a306cb9483c98560b79 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -59,6 +59,13 @@ public class LevelChunk extends ChunkAccess {
         @Override
         public void tick() {}
 
+        // Folia start - region threading
+        @Override
+        public BlockEntity getTileEntity() {
+            return null;
+        }
+        // Folia end - region threading
+
         @Override
         public boolean isRemoved() {
             return true;
@@ -412,6 +419,7 @@ public class LevelChunk extends ChunkAccess {
 
     @Nullable
     public BlockState setBlockState(BlockPos blockposition, BlockState iblockdata, boolean flag, boolean doPlace) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.level, blockposition, "Updating block asynchronously"); // Folia - region threading
         // CraftBukkit end
         int i = blockposition.getY();
         LevelChunkSection chunksection = this.getSection(this.getSectionIndex(i));
@@ -462,7 +470,7 @@ public class LevelChunk extends ChunkAccess {
                     return null;
                 } else {
                     // CraftBukkit - Don't place while processing the BlockPlaceEvent, unless it's a BlockContainer. Prevents blocks such as TNT from activating when cancelled.
-                    if (!this.level.isClientSide && doPlace && (!this.level.captureBlockStates || block instanceof net.minecraft.world.level.block.BaseEntityBlock)) {
+                    if (!this.level.isClientSide && doPlace && (!this.level.getCurrentWorldData().captureBlockStates || block instanceof net.minecraft.world.level.block.BaseEntityBlock)) { // Folia - region threading
                         iblockdata.onPlace(this.level, blockposition, iblockdata1, flag);
                     }
 
@@ -508,7 +516,7 @@ public class LevelChunk extends ChunkAccess {
     @Nullable
     public BlockEntity getBlockEntity(BlockPos pos, LevelChunk.EntityCreationType creationType) {
         // CraftBukkit start
-        BlockEntity tileentity = this.level.capturedTileEntities.get(pos);
+        BlockEntity tileentity = this.level.getCurrentWorldData().capturedTileEntities.get(pos); // Folia - region threading
         if (tileentity == null) {
             tileentity = (BlockEntity) this.blockEntities.get(pos);
         }
@@ -795,13 +803,13 @@ public class LevelChunk extends ChunkAccess {
 
                 org.bukkit.World world = this.level.getWorld();
                 if (world != null) {
-                    this.level.populating = true;
+                    this.level.getCurrentWorldData().populating = true; // Folia - region threading
                     try {
                         for (org.bukkit.generator.BlockPopulator populator : world.getPopulators()) {
                             populator.populate(world, random, bukkitChunk);
                         }
                     } finally {
-                        this.level.populating = false;
+                        this.level.getCurrentWorldData().populating = false; // Folia - region threading
                     }
                 }
                 server.getPluginManager().callEvent(new org.bukkit.event.world.ChunkPopulateEvent(bukkitChunk));
@@ -851,7 +859,7 @@ public class LevelChunk extends ChunkAccess {
     @Override
     public boolean isUnsaved() {
         // Paper start - add dirty system to tick lists
-        long gameTime = this.level.getLevelData().getGameTime();
+        long gameTime = this.level.getRedstoneGameTime(); // Folia - region threading
         if (this.blockTicks.isDirty(gameTime) || this.fluidTicks.isDirty(gameTime)) {
             return true;
         }
@@ -1117,6 +1125,13 @@ public class LevelChunk extends ChunkAccess {
             this.ticker = wrapped;
         }
 
+        // Folia start - region threading
+        @Override
+        public BlockEntity getTileEntity() {
+            return this.ticker == null ? null : this.ticker.getTileEntity();
+        }
+        // Folia end - region threading
+
         @Override
         public void tick() {
             this.ticker.tick();
@@ -1153,6 +1168,13 @@ public class LevelChunk extends ChunkAccess {
             this.ticker = blockentityticker;
         }
 
+        // Folia start - region threading
+        @Override
+        public BlockEntity getTileEntity() {
+            return this.blockEntity;
+        }
+        // Folia end - region threading
+
         @Override
         public void tick() {
             if (!this.blockEntity.isRemoved() && this.blockEntity.hasLevel()) {
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
index d312ce27364f84d32dec8d58a2b37a8a6ad756af..c1629db60017acccc0cf246941afa02c03048bbb 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
@@ -645,7 +645,7 @@ public class ChunkSerializer {
     }
 
     private static void saveTicks(ServerLevel world, CompoundTag nbt, ChunkAccess.TicksToSave tickSchedulers) {
-        long i = world.getLevelData().getGameTime();
+        long i = world.getRedstoneGameTime(); // Folia - region threading
 
         nbt.put("block_ticks", tickSchedulers.blocks().save(i, (block) -> {
             return BuiltInRegistries.BLOCK.getKey(block).toString();
diff --git a/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java b/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java
index d4f903c402765c6e8e1db99e148613748f530726..9568ec33e2b0efdb536930edb44d46e082b86152 100644
--- a/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java
+++ b/src/main/java/net/minecraft/world/level/dimension/end/EndDragonFight.java
@@ -76,7 +76,7 @@ public class EndDragonFight {
     private static final Component DEFAULT_BOSS_EVENT_NAME = Component.translatable("entity.minecraft.ender_dragon"); // Paper - ensure reset EnderDragon boss event name
     public final ServerBossEvent dragonEvent;
     public final ServerLevel level;
-    private final BlockPos origin;
+    public final BlockPos origin; // Folia - region threading
     public final ObjectArrayList<Integer> gateways;
     private final BlockPattern exitPortalPattern;
     private int ticksSinceDragonSeen;
@@ -152,7 +152,7 @@ public class EndDragonFight {
 
         if (!this.dragonEvent.getPlayers().isEmpty()) {
             this.level.getChunkSource().addRegionTicket(TicketType.DRAGON, new ChunkPos(0, 0), 9, Unit.INSTANCE);
-            boolean flag = this.isArenaLoaded();
+            boolean flag = this.isArenaLoaded(); if (!flag) { return; } // Folia - region threading - don't tick if we don't own the entire region
 
             if (this.needsStateScanning && flag) {
                 this.scanState();
@@ -201,6 +201,12 @@ public class EndDragonFight {
         }
 
         List<? extends EnderDragon> list = this.level.getDragons();
+        // Folia start - region threading
+        // we do not want to deal with any dragons NOT nearby
+        list.removeIf((dragon) -> {
+            return !io.papermc.paper.util.TickThread.isTickThreadFor(dragon);
+        });
+        // Folia end - region threading
 
         if (list.isEmpty()) {
             this.dragonKilled = true;
@@ -347,9 +353,8 @@ public class EndDragonFight {
 
             for (int i = -8 + chunkcoordintpair.x; i <= 8 + chunkcoordintpair.x; ++i) {
                 for (int j = 8 + chunkcoordintpair.z; j <= 8 + chunkcoordintpair.z; ++j) {
-                    ChunkAccess ichunkaccess = this.level.getChunk(i, j, ChunkStatus.FULL, false);
-
-                    if (!(ichunkaccess instanceof LevelChunk)) {
+                    ChunkAccess ichunkaccess = this.level.getChunkIfLoaded(i, j); // Folia - region threading
+                    if (!(ichunkaccess instanceof LevelChunk) || !io.papermc.paper.util.TickThread.isTickThreadFor(this.level, i, j, this.level.regioniser.regionSectionChunkSize)) { // Folia - region threading
                         return false;
                     }
 
@@ -536,6 +541,11 @@ public class EndDragonFight {
     }
 
     public void onCrystalDestroyed(EndCrystal enderCrystal, DamageSource source) {
+        // Folia start - region threading
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(this.level, this.origin)) {
+            return;
+        }
+        // Folia end - region threading
         if (this.respawnStage != null && this.respawnCrystals.contains(enderCrystal)) {
             EndDragonFight.LOGGER.debug("Aborting respawn sequence");
             this.respawnStage = null;
@@ -564,7 +574,7 @@ public class EndDragonFight {
 
     public boolean tryRespawn(@Nullable BlockPos placedEndCrystalPos) { // placedEndCrystalPos is null if the tryRespawn() call was not caused by a placed end crystal
         // Paper end - Perf: Do crystal-portal proximity check before entity lookup
-        if (this.dragonKilled && this.respawnStage == null) {
+        if (this.dragonKilled && this.respawnStage == null && io.papermc.paper.util.TickThread.isTickThreadFor(this.level, this.origin)) { // Folia - region threading
             BlockPos blockposition = this.portalLocation;
 
             if (blockposition == null) {
diff --git a/src/main/java/net/minecraft/world/level/levelgen/PatrolSpawner.java b/src/main/java/net/minecraft/world/level/levelgen/PatrolSpawner.java
index 1c4dafdfb3898b5efe06d66792b1b0841ec5724d..8115eb2b632f6aa8d624bddc83c23e281727407f 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/PatrolSpawner.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/PatrolSpawner.java
@@ -19,7 +19,7 @@ import net.minecraft.world.level.block.state.BlockState;
 
 public class PatrolSpawner implements CustomSpawner {
 
-    private int nextTick;
+    //private int nextTick; // Folia - region threading
 
     public PatrolSpawner() {}
 
@@ -32,15 +32,16 @@ public class PatrolSpawner implements CustomSpawner {
             return 0;
         } else {
             RandomSource randomsource = world.random;
+            io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
 
             // Paper start - Pillager patrol spawn settings and per player options
             // Random player selection moved up for per player spawning and configuration
-            int j = world.players().size();
+            int j = world.getLocalPlayers().size(); // Folia - region threading
             if (j < 1) {
                 return 0;
             }
 
-            net.minecraft.server.level.ServerPlayer entityhuman = world.players().get(randomsource.nextInt(j));
+            net.minecraft.server.level.ServerPlayer entityhuman = world.getLocalPlayers().get(randomsource.nextInt(j)); // Folia - region threading
             if (entityhuman.isSpectator()) {
                 return 0;
             }
@@ -50,8 +51,8 @@ public class PatrolSpawner implements CustomSpawner {
                 --entityhuman.patrolSpawnDelay;
                 patrolSpawnDelay = entityhuman.patrolSpawnDelay;
             } else {
-                this.nextTick--;
-                patrolSpawnDelay = this.nextTick;
+                worldData.patrolSpawnerNextTick--; // Folia - region threading
+                patrolSpawnDelay = worldData.patrolSpawnerNextTick; // Folia - region threading
             }
 
             if (patrolSpawnDelay > 0) {
@@ -66,7 +67,7 @@ public class PatrolSpawner implements CustomSpawner {
                 if (world.paperConfig().entities.behavior.pillagerPatrols.spawnDelay.perPlayer) {
                     entityhuman.patrolSpawnDelay += world.paperConfig().entities.behavior.pillagerPatrols.spawnDelay.ticks + randomsource.nextInt(1200);
                 } else {
-                    this.nextTick += world.paperConfig().entities.behavior.pillagerPatrols.spawnDelay.ticks + randomsource.nextInt(1200);
+                    worldData.patrolSpawnerNextTick += world.paperConfig().entities.behavior.pillagerPatrols.spawnDelay.ticks + randomsource.nextInt(1200); // Folia - region threading
                 }
 
                 if (days >= world.paperConfig().entities.behavior.pillagerPatrols.start.day && world.isDay()) {
diff --git a/src/main/java/net/minecraft/world/level/levelgen/PhantomSpawner.java b/src/main/java/net/minecraft/world/level/levelgen/PhantomSpawner.java
index ed80960777b18faca2d6a99783e53daf5fa19e09..b52455178290dd27478da4c062863562942ae2ba 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/PhantomSpawner.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/PhantomSpawner.java
@@ -22,7 +22,7 @@ import net.minecraft.world.level.material.FluidState;
 
 public class PhantomSpawner implements CustomSpawner {
 
-    private int nextTick;
+    //private int nextTick; // Folia - region threading
 
     public PhantomSpawner() {}
 
@@ -40,20 +40,22 @@ public class PhantomSpawner implements CustomSpawner {
             // Paper end - Ability to control player's insomnia and phantoms
             RandomSource randomsource = world.random;
 
-            --this.nextTick;
-            if (this.nextTick > 0) {
+            io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+
+            --worldData.phantomSpawnerNextTick; // Folia - region threading
+            if (worldData.phantomSpawnerNextTick > 0) { // Folia - region threading
                 return 0;
             } else {
                 // Paper start - Ability to control player's insomnia and phantoms
                 int spawnAttemptMinSeconds = world.paperConfig().entities.behavior.phantomsSpawnAttemptMinSeconds;
                 int spawnAttemptMaxSeconds = world.paperConfig().entities.behavior.phantomsSpawnAttemptMaxSeconds;
-                this.nextTick += (spawnAttemptMinSeconds + randomsource.nextInt(spawnAttemptMaxSeconds - spawnAttemptMinSeconds + 1)) * 20;
+                worldData.phantomSpawnerNextTick += (spawnAttemptMinSeconds + randomsource.nextInt(spawnAttemptMaxSeconds - spawnAttemptMinSeconds + 1)) * 20; // Folia - region threading
                 // Paper end - Ability to control player's insomnia and phantoms
                 if (world.getSkyDarken() < 5 && world.dimensionType().hasSkyLight()) {
                     return 0;
                 } else {
                     int i = 0;
-                    Iterator iterator = world.players().iterator();
+                    Iterator iterator = world.getLocalPlayers().iterator(); // Folia - region threading
 
                     while (iterator.hasNext()) {
                         ServerPlayer entityplayer = (ServerPlayer) iterator.next();
diff --git a/src/main/java/net/minecraft/world/level/levelgen/structure/StructureStart.java b/src/main/java/net/minecraft/world/level/levelgen/structure/StructureStart.java
index 1695cff01932d435848e230921d1680b69a41d73..71658657fdaa858ffd388bb19218c30d84f3d77b 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/structure/StructureStart.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/structure/StructureStart.java
@@ -28,7 +28,7 @@ public final class StructureStart {
     private final Structure structure;
     private final PiecesContainer pieceContainer;
     private final ChunkPos chunkPos;
-    private int references;
+    private final java.util.concurrent.atomic.AtomicInteger references; // Folia - region threading
     @Nullable
     private volatile BoundingBox cachedBoundingBox;
 
@@ -41,7 +41,7 @@ public final class StructureStart {
     public StructureStart(Structure structure, ChunkPos pos, int references, PiecesContainer children) {
         this.structure = structure;
         this.chunkPos = pos;
-        this.references = references;
+        this.references = new java.util.concurrent.atomic.AtomicInteger(references); // Folia - region threading
         this.pieceContainer = children;
     }
 
@@ -137,7 +137,7 @@ public final class StructureStart {
             nbttagcompound.putString("id", context.registryAccess().registryOrThrow(Registries.STRUCTURE).getKey(this.structure).toString());
             nbttagcompound.putInt("ChunkX", chunkPos.x);
             nbttagcompound.putInt("ChunkZ", chunkPos.z);
-            nbttagcompound.putInt("references", this.references);
+            nbttagcompound.putInt("references", this.references.get()); // Folia - region threading
             nbttagcompound.put("Children", this.pieceContainer.save(context));
             return nbttagcompound;
         } else {
@@ -155,15 +155,29 @@ public final class StructureStart {
     }
 
     public boolean canBeReferenced() {
-        return this.references < this.getMaxReferences();
+        throw new UnsupportedOperationException("Use tryReference()"); // Folia - region threading
     }
 
+    // Folia start - region threading
+    public boolean tryReference() {
+        for (int curr = this.references.get();;) {
+            if (curr >= this.getMaxReferences()) {
+                return false;
+            }
+
+            if (curr == (curr = this.references.compareAndExchange(curr, curr + 1))) {
+                return true;
+            } // else: try again
+        }
+    }
+    // Folia end - region threading
+
     public void addReference() {
-        ++this.references;
+       throw new UnsupportedOperationException("Use tryReference()"); // Folia - region threading
     }
 
     public int getReferences() {
-        return this.references;
+        return this.references.get(); // Folia - region threading
     }
 
     protected int getMaxReferences() {
diff --git a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
index 5d4c18b068f41f349bdccec14e08ca6ca7cb0c6c..4945bf03176e1842ae3e1bdd4708e39b0a3bdc07 100644
--- a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
+++ b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
@@ -89,10 +89,10 @@ public class PortalForcer {
             BlockPos blockposition1 = villageplacerecord.getPos();
 
             this.level.getChunkSource().addRegionTicket(TicketType.PORTAL, new ChunkPos(blockposition1), 3, blockposition1);
-            BlockState iblockdata = this.level.getBlockState(blockposition1);
+            BlockState iblockdata = this.level.getBlockStateFromEmptyChunk(blockposition1); // Folia - region threading
 
             return BlockUtil.getLargestRectangleAround(blockposition1, (Direction.Axis) iblockdata.getValue(BlockStateProperties.HORIZONTAL_AXIS), 21, Direction.Axis.Y, 21, (blockposition2) -> {
-                return this.level.getBlockState(blockposition2) == iblockdata;
+                return this.level.getBlockStateFromEmptyChunk(blockposition2) == iblockdata; // Folia - region threading
             });
         });
     }
diff --git a/src/main/java/net/minecraft/world/level/redstone/CollectingNeighborUpdater.java b/src/main/java/net/minecraft/world/level/redstone/CollectingNeighborUpdater.java
index 106af2b2c7ff72c7549975aef75cdcff8d9a7d97..67be58de9f684e440b62541365c079cfffe30e51 100644
--- a/src/main/java/net/minecraft/world/level/redstone/CollectingNeighborUpdater.java
+++ b/src/main/java/net/minecraft/world/level/redstone/CollectingNeighborUpdater.java
@@ -48,6 +48,7 @@ public class CollectingNeighborUpdater implements NeighborUpdater {
     }
 
     private void addAndRun(BlockPos pos, CollectingNeighborUpdater.NeighborUpdates entry) {
+        io.papermc.paper.util.TickThread.ensureTickThread((net.minecraft.server.level.ServerLevel)this.level, pos, "Adding block without owning region"); // Folia - region threading
         boolean bl = this.count > 0;
         boolean bl2 = this.maxChainedNeighborUpdates >= 0 && this.count >= this.maxChainedNeighborUpdates;
         this.count++;
diff --git a/src/main/java/net/minecraft/world/level/saveddata/SavedData.java b/src/main/java/net/minecraft/world/level/saveddata/SavedData.java
index 0655a26a58b3df19d81b18abf6b8ab81fd000ef7..d222b102abdd71b9487e11b4b7637be0d129bb2b 100644
--- a/src/main/java/net/minecraft/world/level/saveddata/SavedData.java
+++ b/src/main/java/net/minecraft/world/level/saveddata/SavedData.java
@@ -13,7 +13,7 @@ import org.slf4j.Logger;
 
 public abstract class SavedData {
     private static final Logger LOGGER = LogUtils.getLogger();
-    private boolean dirty;
+    private volatile boolean dirty; // Folia - make map data thread-safe
 
     public abstract CompoundTag save(CompoundTag nbt);
 
@@ -36,6 +36,7 @@ public abstract class SavedData {
 
     public java.util.concurrent.CompletableFuture<Void> save(File file, @org.jetbrains.annotations.Nullable java.util.concurrent.ExecutorService ioExecutor) { // Paper - Write SavedData IO async
         if (this.isDirty()) {
+            this.setDirty(false); // Folia - make map data thread-safe - move before save, so that any changes after are not lost
             CompoundTag compoundTag = new CompoundTag();
             compoundTag.put("data", this.save(new CompoundTag()));
             NbtUtils.addCurrentDataVersion(compoundTag);
@@ -48,7 +49,7 @@ public abstract class SavedData {
             }
             }; // Paper - Write SavedData IO async
 
-            this.setDirty(false);
+            // Folia - make map data thread-safe - move before save, so that any changes after are not lost
             // Paper start - Write SavedData IO async
             if (ioExecutor == null) {
                 return java.util.concurrent.CompletableFuture.runAsync(writeRunnable); // No executor, just use common pool
diff --git a/src/main/java/net/minecraft/world/level/saveddata/maps/MapIndex.java b/src/main/java/net/minecraft/world/level/saveddata/maps/MapIndex.java
index 7640752188b9cb62f19e20b832f39d009cbcb62f..b158e9f2f3a97d2f88f1fb43825f1192650c0924 100644
--- a/src/main/java/net/minecraft/world/level/saveddata/maps/MapIndex.java
+++ b/src/main/java/net/minecraft/world/level/saveddata/maps/MapIndex.java
@@ -33,17 +33,21 @@ public class MapIndex extends SavedData {
 
     @Override
     public CompoundTag save(CompoundTag nbt) {
+        synchronized (this.usedAuxIds) { // Folia - make map data thread-safe
         for (Entry<String> entry : this.usedAuxIds.object2IntEntrySet()) {
             nbt.putInt(entry.getKey(), entry.getIntValue());
         }
+        } // Folia - make map data thread-safe
 
         return nbt;
     }
 
     public int getFreeAuxValueForMap() {
+        synchronized (this.usedAuxIds) { // Folia - make map data thread-safe
         int i = this.usedAuxIds.getInt("map") + 1;
         this.usedAuxIds.put("map", i);
         this.setDirty();
         return i;
+        } // Folia - make map data thread-safe
     }
 }
diff --git a/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java b/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java
index 45269115e63cfc3bd7dc740a5694e2cc7c35bcb1..df799198d4d77a1827002d6d192ebaea3007d5b8 100644
--- a/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java
+++ b/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java
@@ -192,7 +192,7 @@ public class MapItemSavedData extends SavedData {
     }
 
     @Override
-    public CompoundTag save(CompoundTag nbt) {
+    public synchronized CompoundTag save(CompoundTag nbt) { // Folia - make map data thread-safe
         DataResult<Tag> dataresult = ResourceLocation.CODEC.encodeStart(NbtOps.INSTANCE, this.dimension.location()); // CraftBukkit - decompile error
         Logger logger = MapItemSavedData.LOGGER;
 
@@ -249,7 +249,7 @@ public class MapItemSavedData extends SavedData {
         return nbt;
     }
 
-    public MapItemSavedData locked() {
+    public synchronized MapItemSavedData locked() { // Folia - make map data thread-safe
         MapItemSavedData worldmap = new MapItemSavedData(this.centerX, this.centerZ, this.scale, this.trackingPosition, this.unlimitedTracking, true, this.dimension);
 
         worldmap.bannerMarkers.putAll(this.bannerMarkers);
@@ -260,11 +260,12 @@ public class MapItemSavedData extends SavedData {
         return worldmap;
     }
 
-    public MapItemSavedData scaled(int zoomOutScale) {
+    public synchronized MapItemSavedData scaled(int zoomOutScale) { // Folia - make map data thread-safe
         return MapItemSavedData.createFresh((double) this.centerX, (double) this.centerZ, (byte) Mth.clamp(this.scale + zoomOutScale, 0, 4), this.trackingPosition, this.unlimitedTracking, this.dimension);
     }
 
-    public void tickCarriedBy(Player player, ItemStack stack) {
+    public synchronized void tickCarriedBy(Player player, ItemStack stack) { // Folia - make map data thread-safe
+        io.papermc.paper.util.TickThread.ensureTickThread(player, "Ticking map player in incorrect region"); // Folia - region threading
         if (!this.carriedByPlayers.containsKey(player)) {
             MapItemSavedData.HoldingPlayer worldmap_worldmaphumantracker = new MapItemSavedData.HoldingPlayer(player);
 
@@ -373,7 +374,7 @@ public class MapItemSavedData extends SavedData {
             rotation += rotation < 0.0D ? -8.0D : 8.0D;
             b2 = (byte) ((int) (rotation * 16.0D / 360.0D));
             if (this.dimension == Level.NETHER && world != null) {
-                int j = (int) (world.getLevelData().getDayTime() / 10L);
+                int j = (int) (world.getLevelData().getDayTime() / 10L); // Folia - region threading - TODO
 
                 b2 = (byte) (j * j * 34187121 + j * 121 >> 15 & 15);
             }
@@ -432,14 +433,14 @@ public class MapItemSavedData extends SavedData {
     }
 
     @Nullable
-    public Packet<?> getUpdatePacket(int id, Player player) {
+    public synchronized Packet<?> getUpdatePacket(int id, Player player) { // Folia - make map data thread-safe
         MapItemSavedData.HoldingPlayer worldmap_worldmaphumantracker = (MapItemSavedData.HoldingPlayer) this.carriedByPlayers.get(player);
 
         return worldmap_worldmaphumantracker == null ? null : worldmap_worldmaphumantracker.nextUpdatePacket(id);
     }
 
-    public void setColorsDirty(int x, int z) {
-        this.setDirty();
+    public synchronized void setColorsDirty(int x, int z) { // Folia - make map data thread-safe
+        // Folia - make dirty only after updating data - moved down
         Iterator iterator = this.carriedBy.iterator();
 
         while (iterator.hasNext()) {
@@ -447,15 +448,16 @@ public class MapItemSavedData extends SavedData {
 
             worldmap_worldmaphumantracker.markColorsDirty(x, z);
         }
-
+        this.setDirty(); // Folia - make dirty only after updating data - moved from above
     }
 
-    public void setDecorationsDirty() {
-        this.setDirty();
+    public synchronized void setDecorationsDirty() { // Folia - make map data thread-safe
+        // Folia - make dirty only after updating data - moved down
         this.carriedBy.forEach(MapItemSavedData.HoldingPlayer::markDecorationsDirty);
+        this.setDirty(); // Folia - make dirty only after updating data - moved from above
     }
 
-    public MapItemSavedData.HoldingPlayer getHoldingPlayer(Player player) {
+    public synchronized MapItemSavedData.HoldingPlayer getHoldingPlayer(Player player) { // Folia - make map data thread-safe
         MapItemSavedData.HoldingPlayer worldmap_worldmaphumantracker = (MapItemSavedData.HoldingPlayer) this.carriedByPlayers.get(player);
 
         if (worldmap_worldmaphumantracker == null) {
@@ -467,7 +469,7 @@ public class MapItemSavedData extends SavedData {
         return worldmap_worldmaphumantracker;
     }
 
-    public boolean toggleBanner(LevelAccessor world, BlockPos pos) {
+    public synchronized boolean toggleBanner(LevelAccessor world, BlockPos pos) { // Folia - make map data thread-safe
         double d0 = (double) pos.getX() + 0.5D;
         double d1 = (double) pos.getZ() + 0.5D;
         int i = 1 << this.scale;
@@ -476,7 +478,7 @@ public class MapItemSavedData extends SavedData {
         boolean flag = true;
 
         if (d2 >= -63.0D && d3 >= -63.0D && d2 <= 63.0D && d3 <= 63.0D) {
-            MapBanner mapiconbanner = MapBanner.fromWorld(world, pos);
+            MapBanner mapiconbanner = world.getChunkIfLoadedImmediately(pos.getX() >> 4, pos.getZ() >> 4) == null || !io.papermc.paper.util.TickThread.isTickThreadFor(world.getMinecraftWorld(), pos) ? null : MapBanner.fromWorld(world, pos); // Folia - make map data thread-safe - don't sync load or read data we do not own
 
             if (mapiconbanner == null) {
                 return false;
@@ -497,7 +499,7 @@ public class MapItemSavedData extends SavedData {
         return false;
     }
 
-    public void checkBanners(BlockGetter world, int x, int z) {
+    public synchronized void checkBanners(BlockGetter world, int x, int z) { // Folia - make map data thread-safe
         Iterator iterator = this.bannerMarkers.values().iterator();
 
         while (iterator.hasNext()) {
@@ -519,12 +521,12 @@ public class MapItemSavedData extends SavedData {
         return this.bannerMarkers.values();
     }
 
-    public void removedFromFrame(BlockPos pos, int id) {
+    public synchronized void removedFromFrame(BlockPos pos, int id) { // Folia - make map data thread-safe
         this.removeDecoration("frame-" + id);
         this.frameMarkers.remove(MapFrame.frameId(pos));
     }
 
-    public boolean updateColor(int x, int z, byte color) {
+    public synchronized boolean updateColor(int x, int z, byte color) { // Folia - make map data thread-safe
         byte b1 = this.colors[x + z * 128];
 
         if (b1 != color) {
@@ -535,12 +537,12 @@ public class MapItemSavedData extends SavedData {
         }
     }
 
-    public void setColor(int x, int z, byte color) {
+    public synchronized void setColor(int x, int z, byte color) { // Folia - make map data thread-safe
         this.colors[x + z * 128] = color;
         this.setColorsDirty(x, z);
     }
 
-    public boolean isExplorationMap() {
+    public synchronized boolean isExplorationMap() { // Folia - make map data thread-safe
         Iterator iterator = this.decorations.values().iterator();
 
         MapDecoration mapicon;
@@ -575,7 +577,7 @@ public class MapItemSavedData extends SavedData {
         return this.decorations.values();
     }
 
-    public boolean isTrackedCountOverLimit(int iconCount) {
+    public synchronized boolean isTrackedCountOverLimit(int iconCount) { // Folia - make map data thread-safe
         return this.trackedDecorationCount >= iconCount;
     }
 
@@ -701,11 +703,13 @@ public class MapItemSavedData extends SavedData {
         }
 
         public void applyToMap(MapItemSavedData mapState) {
+            synchronized (mapState) { // Folia - make map data thread-safe
             for (int i = 0; i < this.width; ++i) {
                 for (int j = 0; j < this.height; ++j) {
                     mapState.setColor(this.startX + i, this.startY + j, this.mapColors[i + j * this.width]);
                 }
             }
+            } // Folia - make map data thread-safe
 
         }
     }
diff --git a/src/main/java/net/minecraft/world/level/storage/DimensionDataStorage.java b/src/main/java/net/minecraft/world/level/storage/DimensionDataStorage.java
index b89bd2d046e99d0c4848579a5ab4385453358b89..2c000f830ca3b99b13546ae2edd7e90059290543 100644
--- a/src/main/java/net/minecraft/world/level/storage/DimensionDataStorage.java
+++ b/src/main/java/net/minecraft/world/level/storage/DimensionDataStorage.java
@@ -39,6 +39,7 @@ public class DimensionDataStorage implements java.io.Closeable { // Paper - Writ
     }
 
     public <T extends SavedData> T computeIfAbsent(SavedData.Factory<T> type, String id) {
+        synchronized (this.cache) { // Folia - make map data thread-safe
         T savedData = this.get(type, id);
         if (savedData != null) {
             return savedData;
@@ -47,10 +48,12 @@ public class DimensionDataStorage implements java.io.Closeable { // Paper - Writ
             this.set(id, savedData2);
             return savedData2;
         }
+        } // Folia - make map data thread-safe
     }
 
     @Nullable
     public <T extends SavedData> T get(SavedData.Factory<T> type, String id) {
+        synchronized (this.cache) { // Folia - make map data thread-safe
         SavedData savedData = this.cache.get(id);
         if (savedData == null && !this.cache.containsKey(id)) {
             savedData = this.readSavedData(type.deserializer(), type.type(), id);
@@ -58,6 +61,7 @@ public class DimensionDataStorage implements java.io.Closeable { // Paper - Writ
         }
 
         return (T)savedData;
+        } // Folia - make map data thread-safe
     }
 
     @Nullable
@@ -76,7 +80,9 @@ public class DimensionDataStorage implements java.io.Closeable { // Paper - Writ
     }
 
     public void set(String id, SavedData state) {
+        synchronized (this.cache) { // Folia - make map data thread-safe
         this.cache.put(id, state);
+        } // Folia - make map data thread-safe
     }
 
     public CompoundTag readTagFromDisk(String id, DataFixTypes dataFixTypes, int currentSaveVersion) throws IOException {
diff --git a/src/main/java/net/minecraft/world/ticks/LevelChunkTicks.java b/src/main/java/net/minecraft/world/ticks/LevelChunkTicks.java
index 2cdd18f724296f10cd4a522d1e8196723d39cf45..b329d8327d73fc90586945834305fc3a50610c6e 100644
--- a/src/main/java/net/minecraft/world/ticks/LevelChunkTicks.java
+++ b/src/main/java/net/minecraft/world/ticks/LevelChunkTicks.java
@@ -38,6 +38,21 @@ public class LevelChunkTicks<T> implements SerializableTickContainer<T>, TickCon
         this.dirty = false;
     }
     // Paper end - add dirty flag
+    // Folia start - region threading
+    public void offsetTicks(final long offset) {
+        if (offset == 0 || this.tickQueue.isEmpty()) {
+            return;
+        }
+        final ScheduledTick<T>[] queue = this.tickQueue.toArray(new ScheduledTick[0]);
+        this.tickQueue.clear();
+        for (final ScheduledTick<T> entry : queue) {
+            final ScheduledTick<T> newEntry = new ScheduledTick<>(
+                entry.type(), entry.pos(), entry.triggerTick() + offset, entry.subTickOrder()
+            );
+            this.tickQueue.add(newEntry);
+        }
+    }
+    // Folia end - region threading
 
     public LevelChunkTicks() {
     }
diff --git a/src/main/java/net/minecraft/world/ticks/LevelTicks.java b/src/main/java/net/minecraft/world/ticks/LevelTicks.java
index 7a69564572357a7acc043e35b9c113beeb738951..f71661ef4250d3b668fffeea7cd74a28eec95acd 100644
--- a/src/main/java/net/minecraft/world/ticks/LevelTicks.java
+++ b/src/main/java/net/minecraft/world/ticks/LevelTicks.java
@@ -39,12 +39,69 @@ public class LevelTicks<T> implements LevelTickAccess<T> {
     private final List<ScheduledTick<T>> alreadyRunThisTick = new ArrayList<>();
     private final Set<ScheduledTick<?>> toRunThisTickSet = new ObjectOpenCustomHashSet<>(ScheduledTick.UNIQUE_TICK_HASH);
     private final BiConsumer<LevelChunkTicks<T>, ScheduledTick<T>> chunkScheduleUpdater = (chunkTickScheduler, tick) -> {
-        if (tick.equals(chunkTickScheduler.peek())) {
-            this.updateContainerScheduling(tick);
+        if (tick.equals(chunkTickScheduler.peek())) { // Folia - diff on change
+            this.updateContainerScheduling(tick); // Folia - diff on change
         }
     };
 
-    public LevelTicks(LongPredicate tickingFutureReadyPredicate, Supplier<ProfilerFiller> profilerGetter) {
+    // Folia start - region threading
+    public final net.minecraft.server.level.ServerLevel world;
+    public final boolean isBlock;
+
+    public void merge(final LevelTicks<T> into, final long tickOffset) {
+        // note: containersToTick, toRunThisTick, alreadyRunThisTick, toRunThisTickSet
+        // are all transient state, only ever non-empty during tick. But merging regions occurs while there
+        // is no tick happening, so we assume they are empty.
+        for (final java.util.Iterator<Long2ObjectMap.Entry<LevelChunkTicks<T>>> iterator =
+             ((Long2ObjectOpenHashMap<LevelChunkTicks<T>>)this.allContainers).long2ObjectEntrySet().fastIterator();
+             iterator.hasNext();) {
+            final Long2ObjectMap.Entry<LevelChunkTicks<T>> entry = iterator.next();
+            final LevelChunkTicks<T> tickContainer = entry.getValue();
+            tickContainer.offsetTicks(tickOffset);
+            into.allContainers.put(entry.getLongKey(), tickContainer);
+        }
+        for (final java.util.Iterator<Long2LongMap.Entry> iterator = ((Long2LongOpenHashMap)this.nextTickForContainer).long2LongEntrySet().fastIterator();
+             iterator.hasNext();) {
+            final Long2LongMap.Entry entry = iterator.next();
+            into.nextTickForContainer.put(entry.getLongKey(), entry.getLongValue() + tickOffset);
+        }
+    }
+
+    public void split(final int chunkToRegionShift,
+                      final it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap<LevelTicks<T>> regionToData) {
+        for (final java.util.Iterator<Long2ObjectMap.Entry<LevelChunkTicks<T>>> iterator =
+             ((Long2ObjectOpenHashMap<LevelChunkTicks<T>>)this.allContainers).long2ObjectEntrySet().fastIterator();
+             iterator.hasNext();) {
+            final Long2ObjectMap.Entry<LevelChunkTicks<T>> entry = iterator.next();
+
+            final long chunkKey = entry.getLongKey();
+            final int chunkX = io.papermc.paper.util.CoordinateUtils.getChunkX(chunkKey);
+            final int chunkZ = io.papermc.paper.util.CoordinateUtils.getChunkZ(chunkKey);
+
+            final long regionSectionKey = io.papermc.paper.util.CoordinateUtils.getChunkKey(
+                chunkX >> chunkToRegionShift, chunkZ >> chunkToRegionShift
+            );
+            // Should always be non-null, since containers are removed on unload.
+            regionToData.get(regionSectionKey).allContainers.put(chunkKey, entry.getValue());
+        }
+        for (final java.util.Iterator<Long2LongMap.Entry> iterator = ((Long2LongOpenHashMap)this.nextTickForContainer).long2LongEntrySet().fastIterator();
+             iterator.hasNext();) {
+            final Long2LongMap.Entry entry = iterator.next();
+            final long chunkKey = entry.getLongKey();
+            final int chunkX = io.papermc.paper.util.CoordinateUtils.getChunkX(chunkKey);
+            final int chunkZ = io.papermc.paper.util.CoordinateUtils.getChunkZ(chunkKey);
+
+            final long regionSectionKey = io.papermc.paper.util.CoordinateUtils.getChunkKey(
+                chunkX >> chunkToRegionShift, chunkZ >> chunkToRegionShift
+            );
+
+            // Should always be non-null, since containers are removed on unload.
+            regionToData.get(regionSectionKey).nextTickForContainer.put(chunkKey, entry.getLongValue());
+        }
+    }
+    // Folia end - region threading
+
+    public LevelTicks(LongPredicate tickingFutureReadyPredicate, Supplier<ProfilerFiller> profilerGetter, net.minecraft.server.level.ServerLevel world, boolean isBlock) { this.world = world; this.isBlock = isBlock; // Folia - add world and isBlock
         this.tickCheck = tickingFutureReadyPredicate;
         this.profiler = profilerGetter;
     }
@@ -57,7 +114,17 @@ public class LevelTicks<T> implements LevelTickAccess<T> {
             this.nextTickForContainer.put(l, scheduledTick.triggerTick());
         }
 
-        scheduler.setOnTickAdded(this.chunkScheduleUpdater);
+        // Folia start - region threading
+        final boolean isBlock = this.isBlock;
+        final net.minecraft.server.level.ServerLevel world = this.world;
+        // make sure the lambda contains no reference to this LevelTicks
+        scheduler.setOnTickAdded((chunkTickScheduler, tick) -> {
+            if (tick.equals(chunkTickScheduler.peek())) {
+                io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData();
+                (isBlock ? worldData.getBlockLevelTicks() : worldData.getFluidLevelTicks()).updateContainerScheduling((ScheduledTick)tick);
+            }
+        });
+        // Folia end - region threading
     }
 
     public void removeContainer(ChunkPos pos) {
@@ -71,6 +138,7 @@ public class LevelTicks<T> implements LevelTickAccess<T> {
 
     @Override
     public void schedule(ScheduledTick<T> orderedTick) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, orderedTick.pos(), "Cannot schedule tick for another region!"); // Folia - region threading
         long l = ChunkPos.asLong(orderedTick.pos());
         LevelChunkTicks<T> levelChunkTicks = this.allContainers.get(l);
         if (levelChunkTicks == null) {
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index b63effd92be5a8a75db6c37e5a1b91541020ec75..350fc61fd709453a86c9f7f6e4bccc434065cc35 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -309,7 +309,7 @@ public final class CraftServer implements Server {
     private final CraftPotionBrewer potionBrewer = new CraftPotionBrewer(); // Paper - Custom Potion Mixes
 
     // Paper start - Folia region threading API
-    private final io.papermc.paper.threadedregions.scheduler.FallbackRegionScheduler regionizedScheduler = new io.papermc.paper.threadedregions.scheduler.FallbackRegionScheduler();
+    private final io.papermc.paper.threadedregions.scheduler.FoliaRegionScheduler regionizedScheduler = new io.papermc.paper.threadedregions.scheduler.FoliaRegionScheduler(); // Folia - region threading
     private final io.papermc.paper.threadedregions.scheduler.FoliaAsyncScheduler asyncScheduler = new io.papermc.paper.threadedregions.scheduler.FoliaAsyncScheduler();
     private final io.papermc.paper.threadedregions.scheduler.FoliaGlobalRegionScheduler globalRegionScheduler = new io.papermc.paper.threadedregions.scheduler.FoliaGlobalRegionScheduler();
 
@@ -377,6 +377,12 @@ public final class CraftServer implements Server {
         return io.papermc.paper.util.TickThread.isTickThreadFor(((org.bukkit.craftbukkit.entity.CraftEntity) entity).getHandleRaw());
     }
     // Paper end - Folia reagion threading API
+    // Folia start - region threading API
+    @Override
+    public boolean isGlobalTickThread() {
+        return io.papermc.paper.threadedregions.RegionizedServer.isGlobalTickThread();
+    }
+    // Folia end - region threading API
 
     static {
         ConfigurationSerialization.registerClass(CraftOfflinePlayer.class);
@@ -971,6 +977,9 @@ public final class CraftServer implements Server {
 
     // NOTE: Should only be called from DedicatedServer.ah()
     public boolean dispatchServerCommand(CommandSender sender, ConsoleInput serverCommand) {
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("May not dispatch server commands async");
+        // Folia end - region threading
         if (sender instanceof Conversable) {
             Conversable conversable = (Conversable) sender;
 
@@ -990,12 +999,46 @@ public final class CraftServer implements Server {
         }
     }
 
+    // Folia start - region threading
+    public void dispatchCmdAsync(CommandSender sender, String commandLine) {
+        if ((sender instanceof Entity entity)) {
+            ((org.bukkit.craftbukkit.entity.CraftEntity)entity).taskScheduler.schedule(
+                (nmsEntity) -> {
+                    CraftServer.this.dispatchCommand(nmsEntity.getBukkitEntity(), commandLine);
+                },
+                null,
+                1L
+            );
+        } else if (sender instanceof ConsoleCommandSender || sender instanceof io.papermc.paper.commands.FeedbackForwardingSender) {
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> {
+                CraftServer.this.dispatchCommand(sender, commandLine);
+            });
+        } else {
+            // huh?
+            throw new UnsupportedOperationException("Dispatching command for " + sender);
+        }
+    }
+    // Folia end - region threading
+
     @Override
     public boolean dispatchCommand(CommandSender sender, String commandLine) {
         Preconditions.checkArgument(sender != null, "sender cannot be null");
         Preconditions.checkArgument(commandLine != null, "commandLine cannot be null");
         org.spigotmc.AsyncCatcher.catchOp("Command Dispatched Async: " + commandLine); // Spigot // Paper - Include command in error message
 
+        // Folia start - region threading
+        if ((sender instanceof Entity entity)) {
+            io.papermc.paper.util.TickThread.ensureTickThread(((org.bukkit.craftbukkit.entity.CraftEntity)entity).getHandle(), "Dispatching command async");
+        } else if (sender instanceof ConsoleCommandSender || sender instanceof net.minecraft.server.rcon.RconConsoleSource
+                    || sender instanceof org.bukkit.craftbukkit.command.CraftRemoteConsoleCommandSender
+                    || sender instanceof io.papermc.paper.commands.FeedbackForwardingSender) {
+            io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Dispatching command async");
+        } else {
+            // huh?
+            throw new UnsupportedOperationException("Dispatching command for " + sender);
+        }
+        // Folia end - region threading
+
         if (this.commandMap.dispatch(sender, commandLine)) {
             return true;
         }
@@ -3234,7 +3277,7 @@ public final class CraftServer implements Server {
 
     @Override
     public int getCurrentTick() {
-        return net.minecraft.server.MinecraftServer.currentTick;
+        return (int)io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick(); // Folia - region threading
     }
 
     @Override
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 00357d78182b3ff87e3d9a45705b072af56739c8..f325532b326fd7fe8c36003833890db57371eacc 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -193,7 +193,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public int getTickableTileEntityCount() {
-        return world.blockEntityTickers.size();
+        throw new UnsupportedOperationException(); // Folia - region threading - TODO fix this?
     }
 
     @Override
@@ -255,7 +255,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         // Paper start - per world spawn limits
         for (SpawnCategory spawnCategory : SpawnCategory.values()) {
             if (CraftSpawnCategory.isValidForLimits(spawnCategory)) {
-                setSpawnLimit(spawnCategory, this.world.paperConfig().entities.spawning.spawnLimits.getInt(CraftSpawnCategory.toNMS(spawnCategory)));
+                this.spawnCategoryLimit.put(spawnCategory, this.world.paperConfig().entities.spawning.spawnLimits.getInt(CraftSpawnCategory.toNMS(spawnCategory))); // Folia - region threading
             }
         }
         // Paper end - per world spawn limits
@@ -342,6 +342,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public Chunk getChunkAt(int x, int z) {
+        io.papermc.paper.util.TickThread.isTickThreadFor(this.getHandle(), x, z); // Folia - region threading
         warnUnsafeChunk("getting a faraway chunk", x, z); // Paper
         // Paper start - add ticket to hold chunk for a little while longer if plugin accesses it
         net.minecraft.world.level.chunk.LevelChunk chunk = this.world.getChunkSource().getChunkAtIfLoadedImmediately(x, z);
@@ -365,7 +366,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     // Paper start
     private void addTicket(int x, int z) {
-        io.papermc.paper.util.MCUtil.MAIN_EXECUTOR.execute(() -> this.world.getChunkSource().addRegionTicket(TicketType.PLUGIN, new ChunkPos(x, z), 0, Unit.INSTANCE)); // Paper
+        this.world.getChunkSource().addRegionTicket(TicketType.PLUGIN, new ChunkPos(x, z), 0, Unit.INSTANCE); // Paper // Folia - region threading - does not need to be on the main thread anymore
     }
     // Paper end
 
@@ -384,10 +385,10 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     public boolean isChunkGenerated(int x, int z) {
         // Paper start - Fix this method
-        if (!Bukkit.isPrimaryThread()) {
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(this.getHandle(), x, z)) { // Folia - region threading
             return java.util.concurrent.CompletableFuture.supplyAsync(() -> {
                 return CraftWorld.this.isChunkGenerated(x, z);
-            }, world.getChunkSource().mainThreadProcessor).join();
+            }, (run) -> { io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueChunkTask(this.getHandle(), x, z, run);}).join(); // Folia - region threading
         }
         ChunkAccess chunk = world.getChunkSource().getChunkAtImmediately(x, z);
         if (chunk == null) {
@@ -441,7 +442,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     }
 
     private boolean unloadChunk0(int x, int z, boolean save) {
-        org.spigotmc.AsyncCatcher.catchOp("chunk unload"); // Spigot
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, x, z, "Cannot unload chunk asynchronously"); // Folia - region threading
         if (!this.isChunkLoaded(x, z)) {
             return true;
         }
@@ -456,7 +457,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean regenerateChunk(int x, int z) {
-        org.spigotmc.AsyncCatcher.catchOp("chunk regenerate"); // Spigot
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, x, z, "Cannot regenerate chunk asynchronously"); // Folia - region threading
         warnUnsafeChunk("regenerating a faraway chunk", x, z); // Paper
         // Paper start - implement regenerateChunk method
         final ServerLevel serverLevel = this.world;
@@ -519,6 +520,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean refreshChunk(int x, int z) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, x, z, "Cannot refresh chunk asynchronously"); // Folia - region threading
         ChunkHolder playerChunk = this.world.getChunkSource().chunkMap.getVisibleChunkIfPresent(ChunkPos.asLong(x, z));
         if (playerChunk == null) return false;
 
@@ -554,7 +556,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean loadChunk(int x, int z, boolean generate) {
-        org.spigotmc.AsyncCatcher.catchOp("chunk load"); // Spigot
+        io.papermc.paper.util.TickThread.ensureTickThread(this.getHandle(), x, z, "May not sync load chunks asynchronously"); // Folia - region threading
         warnUnsafeChunk("loading a faraway chunk", x, z); // Paper
         // Paper start - Optimize this method
         ChunkPos chunkPos = new ChunkPos(x, z);
@@ -623,7 +625,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         DistanceManager chunkDistanceManager = this.world.getChunkSource().chunkMap.distanceManager;
 
         if (chunkDistanceManager.addRegionTicketAtDistance(TicketType.PLUGIN_TICKET, new ChunkPos(x, z), 2, plugin)) { // keep in-line with force loading, add at level 31
-            this.getChunkAt(x, z); // ensure loaded
+            //this.getChunkAt(x, z); // ensure loaded // Folia - region threading - do not load chunks for tickets anymore to make this mt-safe
             return true;
         }
 
@@ -833,13 +835,15 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean generateTree(Location loc, TreeType type, BlockChangeDelegate delegate) {
-        this.world.captureTreeGeneration = true;
-        this.world.captureBlockStates = true;
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, loc.getX(), loc.getZ(), "Cannot generate tree asynchronously"); // Folia - region threading
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+        worldData.captureTreeGeneration = true; // Folia - region threading
+        worldData.captureBlockStates = true; // Folia - region threading
         boolean grownTree = this.generateTree(loc, type);
-        this.world.captureBlockStates = false;
-        this.world.captureTreeGeneration = false;
+        worldData.captureBlockStates = false; // Folia - region threading
+        worldData.captureTreeGeneration = false; // Folia - region threading
         if (grownTree) { // Copy block data to delegate
-            for (BlockState blockstate : this.world.capturedBlockStates.values()) {
+            for (BlockState blockstate : worldData.capturedBlockStates.values()) { // Folia - region threading
                 BlockPos position = ((CraftBlockState) blockstate).getPosition();
                 net.minecraft.world.level.block.state.BlockState oldBlock = this.world.getBlockState(position);
                 int flag = ((CraftBlockState) blockstate).getFlag();
@@ -847,10 +851,10 @@ public class CraftWorld extends CraftRegionAccessor implements World {
                 net.minecraft.world.level.block.state.BlockState newBlock = this.world.getBlockState(position);
                 this.world.notifyAndUpdatePhysics(position, null, oldBlock, newBlock, newBlock, flag, 512);
             }
-            this.world.capturedBlockStates.clear();
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             return true;
         } else {
-            this.world.capturedBlockStates.clear();
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             return false;
         }
     }
@@ -884,6 +888,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setTime(long time) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify time off of the global region"); // Folia - region threading
         long margin = (time - this.getFullTime()) % 24000;
         if (margin < 0) margin += 24000;
         this.setFullTime(this.getFullTime() + margin);
@@ -896,6 +901,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setFullTime(long time) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify time off of the global region"); // Folia - region threading
         // Notify anyone who's listening
         TimeSkipEvent event = new TimeSkipEvent(this, TimeSkipEvent.SkipReason.CUSTOM, time - this.world.getDayTime());
         this.server.getPluginManager().callEvent(event);
@@ -923,7 +929,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public long getGameTime() {
-        return this.world.levelData.getGameTime();
+        return this.getHandle().getGameTime(); // Folia - region threading
     }
 
     @Override
@@ -943,11 +949,13 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean createExplosion(double x, double y, double z, float power, boolean setFire, boolean breakBlocks, Entity source) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, x, z, "Cannot create explosion asynchronously");
         return !this.world.explode(source == null ? null : ((CraftEntity) source).getHandle(), x, y, z, power, setFire, breakBlocks ? net.minecraft.world.level.Level.ExplosionInteraction.MOB : net.minecraft.world.level.Level.ExplosionInteraction.NONE).wasCanceled;
     }
     // Paper start
     @Override
     public boolean createExplosion(Entity source, Location loc, float power, boolean setFire, boolean breakBlocks) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, loc.getX(), loc.getZ(), "Cannot create explosion asynchronously");
         return !world.explode(source != null ? ((org.bukkit.craftbukkit.entity.CraftEntity) source).getHandle() : null, loc.getX(), loc.getY(), loc.getZ(), power, setFire, breakBlocks ? net.minecraft.world.level.Level.ExplosionInteraction.MOB : net.minecraft.world.level.Level.ExplosionInteraction.NONE).wasCanceled;
     }
     // Paper end
@@ -1024,6 +1032,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public int getHighestBlockYAt(int x, int z, org.bukkit.HeightMap heightMap) {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, x >> 4, z >> 4, "Cannot retrieve chunk asynchronously"); // Folia - region threading
         warnUnsafeChunk("getting a faraway chunk", x >> 4, z >> 4); // Paper
         // Transient load for this tick
         return this.world.getChunk(x >> 4, z >> 4).getHeight(CraftHeightMap.toNMS(heightMap), x, z);
@@ -1054,6 +1063,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     public void setBiome(int x, int y, int z, Holder<net.minecraft.world.level.biome.Biome> bb) {
         BlockPos pos = new BlockPos(x, 0, z);
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, pos, "Cannot retrieve chunk asynchronously"); // Folia - region threading
         if (this.world.hasChunkAt(pos)) {
             net.minecraft.world.level.chunk.LevelChunk chunk = this.world.getChunkAt(pos);
 
@@ -1364,6 +1374,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setStorm(boolean hasStorm) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify weather off of the global region"); // Folia - region threading
         this.world.serverLevelData.setRaining(hasStorm, org.bukkit.event.weather.WeatherChangeEvent.Cause.PLUGIN); // Paper - Add cause to Weather/ThunderChangeEvents
         this.setWeatherDuration(0); // Reset weather duration (legacy behaviour)
         this.setClearWeatherDuration(0); // Reset clear weather duration (reset "/weather clear" commands)
@@ -1376,6 +1387,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setWeatherDuration(int duration) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify weather off of the global region"); // Folia - region threading
         this.world.serverLevelData.setRainTime(duration);
     }
 
@@ -1386,6 +1398,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setThundering(boolean thundering) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify weather off of the global region"); // Folia - region threading
         this.world.serverLevelData.setThundering(thundering, org.bukkit.event.weather.ThunderChangeEvent.Cause.PLUGIN); // Paper - Add cause to Weather/ThunderChangeEvents
         this.setThunderDuration(0); // Reset weather duration (legacy behaviour)
         this.setClearWeatherDuration(0); // Reset clear weather duration (reset "/weather clear" commands)
@@ -1398,6 +1411,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setThunderDuration(int duration) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify weather off of the global region"); // Folia - region threading
         this.world.serverLevelData.setThunderTime(duration);
     }
 
@@ -1408,6 +1422,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setClearWeatherDuration(int duration) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify weather off of the global region"); // Folia - region threading
         this.world.serverLevelData.setClearWeatherTime(duration);
     }
 
@@ -1602,6 +1617,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setKeepSpawnInMemory(boolean keepLoaded) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify keep spawn in memory off of the global region"); // Folia - region threading
         // Paper start - Configurable spawn radius
         if (keepLoaded == this.world.keepSpawnInMemory) {
             // do nothing, nothing has changed
@@ -1680,6 +1696,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setHardcore(boolean hardcore) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.world.serverLevelData.settings.hardcore = hardcore;
     }
 
@@ -1692,6 +1709,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setTicksPerAnimalSpawns(int ticksPerAnimalSpawns) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setTicksPerSpawns(SpawnCategory.ANIMAL, ticksPerAnimalSpawns);
     }
 
@@ -1704,6 +1722,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setTicksPerMonsterSpawns(int ticksPerMonsterSpawns) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setTicksPerSpawns(SpawnCategory.MONSTER, ticksPerMonsterSpawns);
     }
 
@@ -1716,6 +1735,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setTicksPerWaterSpawns(int ticksPerWaterSpawns) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setTicksPerSpawns(SpawnCategory.WATER_ANIMAL, ticksPerWaterSpawns);
     }
 
@@ -1728,6 +1748,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setTicksPerWaterAmbientSpawns(int ticksPerWaterAmbientSpawns) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setTicksPerSpawns(SpawnCategory.WATER_AMBIENT, ticksPerWaterAmbientSpawns);
     }
 
@@ -1740,6 +1761,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setTicksPerWaterUndergroundCreatureSpawns(int ticksPerWaterUndergroundCreatureSpawns) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setTicksPerSpawns(SpawnCategory.WATER_UNDERGROUND_CREATURE, ticksPerWaterUndergroundCreatureSpawns);
     }
 
@@ -1752,11 +1774,13 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setTicksPerAmbientSpawns(int ticksPerAmbientSpawns) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setTicksPerSpawns(SpawnCategory.AMBIENT, ticksPerAmbientSpawns);
     }
 
     @Override
     public void setTicksPerSpawns(SpawnCategory spawnCategory, int ticksPerCategorySpawn) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         Preconditions.checkArgument(spawnCategory != null, "SpawnCategory cannot be null");
         Preconditions.checkArgument(CraftSpawnCategory.isValidForLimits(spawnCategory), "SpawnCategory.%s are not supported", spawnCategory);
 
@@ -1773,21 +1797,25 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setMetadata(String metadataKey, MetadataValue newMetadataValue) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify metadata off of the global region"); // Folia - region threading
         this.server.getWorldMetadata().setMetadata(this, metadataKey, newMetadataValue);
     }
 
     @Override
     public List<MetadataValue> getMetadata(String metadataKey) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot retrieve metadata off of the global region"); // Folia - region threading
         return this.server.getWorldMetadata().getMetadata(this, metadataKey);
     }
 
     @Override
     public boolean hasMetadata(String metadataKey) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot retrieve metadata off of the global region"); // Folia - region threading
         return this.server.getWorldMetadata().hasMetadata(this, metadataKey);
     }
 
     @Override
     public void removeMetadata(String metadataKey, Plugin owningPlugin) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify metadata off of the global region"); // Folia - region threading
         this.server.getWorldMetadata().removeMetadata(this, metadataKey, owningPlugin);
     }
 
@@ -1800,6 +1828,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setMonsterSpawnLimit(int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setSpawnLimit(SpawnCategory.MONSTER, limit);
     }
 
@@ -1812,6 +1841,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setAnimalSpawnLimit(int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setSpawnLimit(SpawnCategory.ANIMAL, limit);
     }
 
@@ -1824,6 +1854,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setWaterAnimalSpawnLimit(int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setSpawnLimit(SpawnCategory.WATER_ANIMAL, limit);
     }
 
@@ -1836,6 +1867,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setWaterAmbientSpawnLimit(int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setSpawnLimit(SpawnCategory.WATER_AMBIENT, limit);
     }
 
@@ -1848,6 +1880,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setWaterUndergroundCreatureSpawnLimit(int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setSpawnLimit(SpawnCategory.WATER_UNDERGROUND_CREATURE, limit);
     }
 
@@ -1860,6 +1893,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     @Override
     @Deprecated
     public void setAmbientSpawnLimit(int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         this.setSpawnLimit(SpawnCategory.AMBIENT, limit);
     }
 
@@ -1882,6 +1916,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void setSpawnLimit(SpawnCategory spawnCategory, int limit) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         Preconditions.checkArgument(spawnCategory != null, "SpawnCategory cannot be null");
         Preconditions.checkArgument(CraftSpawnCategory.isValidForLimits(spawnCategory), "SpawnCategory.%s are not supported", spawnCategory);
 
@@ -1964,7 +1999,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         if (!(entity instanceof CraftEntity craftEntity) || entity.getWorld() != this || sound == null || category == null) return;
 
         ClientboundSoundEntityPacket packet = new ClientboundSoundEntityPacket(CraftSound.bukkitToMinecraftHolder(sound), net.minecraft.sounds.SoundSource.valueOf(category.name()), craftEntity.getHandle(), volume, pitch, seed);
-        ChunkMap.TrackedEntity entityTracker = this.getHandle().getChunkSource().chunkMap.entityMap.get(entity.getEntityId());
+        ChunkMap.TrackedEntity entityTracker = ((CraftEntity) entity).getHandle().tracker; // Folia - region threading
         if (entityTracker != null) {
             entityTracker.broadcastAndSend(packet);
         }
@@ -1976,7 +2011,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         if (!(entity instanceof CraftEntity craftEntity) || entity.getWorld() != this || sound == null || category == null) return;
 
         ClientboundSoundEntityPacket packet = new ClientboundSoundEntityPacket(Holder.direct(SoundEvent.createVariableRangeEvent(new ResourceLocation(sound))), net.minecraft.sounds.SoundSource.valueOf(category.name()), craftEntity.getHandle(), volume, pitch, seed);
-        ChunkMap.TrackedEntity entityTracker = this.getHandle().getChunkSource().chunkMap.entityMap.get(entity.getEntityId());
+        ChunkMap.TrackedEntity entityTracker = ((CraftEntity)entity).getHandle().tracker; // Folia - region threading
         if (entityTracker != null) {
             entityTracker.broadcastAndSend(packet);
         }
@@ -2065,6 +2100,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean setGameRuleValue(String rule, String value) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         // No null values allowed
         if (rule == null || value == null) return false;
 
@@ -2107,6 +2143,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public <T> boolean setGameRule(GameRule<T> rule, T newValue) {
+        io.papermc.paper.threadedregions.RegionizedServer.ensureGlobalTickThread("Cannot modify server settings off of the global region"); // Folia - region threading
         Preconditions.checkArgument(rule != null, "GameRule cannot be null");
         Preconditions.checkArgument(newValue != null, "GameRule value cannot be null");
 
@@ -2359,6 +2396,12 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public void sendGameEvent(Entity sourceEntity, org.bukkit.GameEvent gameEvent, Vector position) {
+        // Folia start - region threading
+        if (sourceEntity != null && !Bukkit.isOwnedByCurrentRegion(sourceEntity)) {
+            throw new IllegalStateException("Cannot send game event asynchronously");
+        }
+        io.papermc.paper.util.TickThread.ensureTickThread(this.world, position.getX(), position.getZ(), "Cannot send game event asynchronously");
+        // Folia end - region threading
         getHandle().gameEvent(sourceEntity != null ? ((CraftEntity) sourceEntity).getHandle(): null, net.minecraft.core.registries.BuiltInRegistries.GAME_EVENT.get(org.bukkit.craftbukkit.util.CraftNamespacedKey.toMinecraft(gameEvent.getKey())), org.bukkit.craftbukkit.util.CraftVector.toBlockPos(position));
     }
     // Paper end
@@ -2487,7 +2530,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
     // Paper start
     public java.util.concurrent.CompletableFuture<Chunk> getChunkAtAsync(int x, int z, boolean gen, boolean urgent) {
         warnUnsafeChunk("getting a faraway chunk async", x, z); // Paper
-        if (Bukkit.isPrimaryThread()) {
+        if (io.papermc.paper.util.TickThread.isTickThreadFor(this.getHandle(), x, z)) { // Folia - region threading
             net.minecraft.world.level.chunk.LevelChunk immediate = this.world.getChunkSource().getChunkAtIfLoadedImmediately(x, z);
             if (immediate != null) {
                 return java.util.concurrent.CompletableFuture.completedFuture(new CraftChunk(immediate));
@@ -2504,7 +2547,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         java.util.concurrent.CompletableFuture<Chunk> ret = new java.util.concurrent.CompletableFuture<>();
 
         io.papermc.paper.chunk.system.ChunkSystem.scheduleChunkLoad(this.getHandle(), x, z, gen, ChunkStatus.FULL, true, priority, (c) -> {
-            net.minecraft.server.MinecraftServer.getServer().scheduleOnMain(() -> {
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().taskQueue.queueTickTaskQueue(this.getHandle(), x, z, () -> { // Folia - region threading
                 net.minecraft.world.level.chunk.LevelChunk chunk = (net.minecraft.world.level.chunk.LevelChunk)c;
                 if (chunk != null) this.addTicket(x, z); // Paper
                 ret.complete(chunk == null ? null : new CraftChunk(chunk));
diff --git a/src/main/java/org/bukkit/craftbukkit/block/CapturedBlockState.java b/src/main/java/org/bukkit/craftbukkit/block/CapturedBlockState.java
index dfe5fa29a29af06640382456ef59aed794f5362b..ba5e47037f4dc3eb3efe86cd31183b39eab823fe 100644
--- a/src/main/java/org/bukkit/craftbukkit/block/CapturedBlockState.java
+++ b/src/main/java/org/bukkit/craftbukkit/block/CapturedBlockState.java
@@ -64,6 +64,7 @@ public final class CapturedBlockState extends CraftBlockState {
 
                 for (int k = 0; k < j; ++k) {
                     Bee entitybee = new Bee(EntityType.BEE, generatoraccessseed.getMinecraftWorld());
+                    entitybee.setPosRaw(blockposition1.getX(), blockposition1.getY(), blockposition1.getZ()); // Folia - region threading - set position so that thread checks do not fail
 
                     tileentitybeehive.addOccupantWithPresetTicks(entitybee, false, random.nextInt(599));
                 }
diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
index ac11f18690434922179b61ffcc3036dea025b0cb..9efe9fce59a0b4fe7315dc41d1e21615b97e5cf6 100644
--- a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+++ b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
@@ -75,6 +75,11 @@ public class CraftBlock implements Block {
     }
 
     public net.minecraft.world.level.block.state.BlockState getNMS() {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         return this.world.getBlockState(this.position);
     }
 
@@ -157,6 +162,11 @@ public class CraftBlock implements Block {
     }
 
     private void setData(final byte data, int flag) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         this.world.setBlock(this.position, CraftMagicNumbers.getBlock(this.getType(), data), flag);
     }
 
@@ -198,6 +208,11 @@ public class CraftBlock implements Block {
     }
 
     public static boolean setTypeAndData(LevelAccessor world, BlockPos position, net.minecraft.world.level.block.state.BlockState old, net.minecraft.world.level.block.state.BlockState blockData, boolean applyPhysics) {
+        // Folia start - region threading
+        if (world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, position, "Cannot modify world asynchronously");
+        }
+        // Folia end - region threading
         // SPIGOT-611: need to do this to prevent glitchiness. Easier to handle this here (like /setblock) than to fix weirdness in tile entity cleanup
         if (old.hasBlockEntity() && blockData.getBlock() != old.getBlock()) { // SPIGOT-3725 remove old tile entity if block changes
             // SPIGOT-4612: faster - just clear tile
@@ -343,18 +358,33 @@ public class CraftBlock implements Block {
 
     @Override
     public Biome getBiome() {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         return this.getWorld().getBiome(this.getX(), this.getY(), this.getZ());
     }
 
     // Paper start
     @Override
     public Biome getComputedBiome() {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         return this.getWorld().getComputedBiome(this.getX(), this.getY(), this.getZ());
     }
     // Paper end
 
     @Override
     public void setBiome(Biome bio) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         this.getWorld().setBiome(this.getX(), this.getY(), this.getZ(), bio);
     }
 
@@ -402,6 +432,11 @@ public class CraftBlock implements Block {
 
     @Override
     public boolean isBlockFaceIndirectlyPowered(BlockFace face) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         int power = this.world.getMinecraftWorld().getSignal(this.position, CraftBlock.blockFaceToNotch(face));
 
         Block relative = this.getRelative(face);
@@ -414,6 +449,11 @@ public class CraftBlock implements Block {
 
     @Override
     public int getBlockPower(BlockFace face) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         int power = 0;
         net.minecraft.world.level.Level world = this.world.getMinecraftWorld();
         int x = this.getX();
@@ -500,6 +540,11 @@ public class CraftBlock implements Block {
 
     @Override
     public boolean breakNaturally(ItemStack item, boolean triggerEffect, boolean dropExperience) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         // Paper end
         // Order matters here, need to drop before setting to air so skulls can get their data
         net.minecraft.world.level.block.state.BlockState iblockdata = this.getNMS();
@@ -543,21 +588,27 @@ public class CraftBlock implements Block {
 
     @Override
     public boolean applyBoneMeal(BlockFace face) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         Direction direction = CraftBlock.blockFaceToNotch(face);
         BlockFertilizeEvent event = null;
         ServerLevel world = this.getCraftWorld().getHandle();
         UseOnContext context = new UseOnContext(world, null, InteractionHand.MAIN_HAND, Items.BONE_MEAL.getDefaultInstance(), new BlockHitResult(Vec3.ZERO, direction, this.getPosition(), false));
 
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
         // SPIGOT-6895: Call StructureGrowEvent and BlockFertilizeEvent
-        world.captureTreeGeneration = true;
+        worldData.captureTreeGeneration = true; // Folia - region threading
         InteractionResult result = BoneMealItem.applyBonemeal(context);
-        world.captureTreeGeneration = false;
+        worldData.captureTreeGeneration = false; // Folia - region threading
 
-        if (world.capturedBlockStates.size() > 0) {
-            TreeType treeType = SaplingBlock.treeType;
-            SaplingBlock.treeType = null;
-            List<BlockState> blocks = new ArrayList<>(world.capturedBlockStates.values());
-            world.capturedBlockStates.clear();
+        if (worldData.capturedBlockStates.size() > 0) { // Folia - region threading
+            TreeType treeType = SaplingBlock.treeTypeRT.get(); // Folia - region threading
+            SaplingBlock.treeTypeRT.set(null); // Folia - region threading
+            List<BlockState> blocks = new ArrayList<>(worldData.capturedBlockStates.values()); // Folia - region threading
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             StructureGrowEvent structureEvent = null;
 
             if (treeType != null) {
@@ -644,6 +695,11 @@ public class CraftBlock implements Block {
 
     @Override
     public RayTraceResult rayTrace(Location start, Vector direction, double maxDistance, FluidCollisionMode fluidCollisionMode) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         Preconditions.checkArgument(start != null, "Location start cannot be null");
         Preconditions.checkArgument(this.getWorld().equals(start.getWorld()), "Location start cannot be a different world");
         start.checkFinite();
@@ -685,6 +741,11 @@ public class CraftBlock implements Block {
 
     @Override
     public boolean canPlace(BlockData data) {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         Preconditions.checkArgument(data != null, "BlockData cannot be null");
         net.minecraft.world.level.block.state.BlockState iblockdata = ((CraftBlockData) data).getState();
         net.minecraft.world.level.Level world = this.world.getMinecraftWorld();
@@ -719,18 +780,32 @@ public class CraftBlock implements Block {
 
     @Override
     public void tick() {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         final ServerLevel level = this.world.getMinecraftWorld();
         this.getNMS().tick(level, this.position, level.random);
     }
 
-
     @Override
     public void fluidTick() {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         this.getNMSFluid().tick(this.world.getMinecraftWorld(), this.position);
     }
 
     @Override
     public void randomTick() {
+        // Folia start - region threading
+        if (this.world instanceof ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, this.position, "Cannot read world asynchronously");
+        }
+        // Folia end - region threading
         final ServerLevel level = this.world.getMinecraftWorld();
         this.getNMS().randomTick(level, this.position, level.random);
     }
diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftBlockState.java b/src/main/java/org/bukkit/craftbukkit/block/CraftBlockState.java
index 2cfaa59a0bb6b5253b5a8dcc38ae65e0f085fd3f..5cf33427847068fc589ada9f731b985f791ac013 100644
--- a/src/main/java/org/bukkit/craftbukkit/block/CraftBlockState.java
+++ b/src/main/java/org/bukkit/craftbukkit/block/CraftBlockState.java
@@ -210,6 +210,12 @@ public class CraftBlockState implements BlockState {
         LevelAccessor access = this.getWorldHandle();
         CraftBlock block = this.getBlock();
 
+        // Folia start - region threading
+        if (access instanceof net.minecraft.server.level.ServerLevel serverWorld) {
+            io.papermc.paper.util.TickThread.ensureTickThread(serverWorld, position, "Cannot modify world asynchronously");
+        }
+        // Folia end - region threading
+
         if (block.getType() != this.getType()) {
             if (!force) {
                 return false;
@@ -340,6 +346,9 @@ public class CraftBlockState implements BlockState {
 
     @Override
     public java.util.Collection<org.bukkit.inventory.ItemStack> getDrops(org.bukkit.inventory.ItemStack item, org.bukkit.entity.Entity entity) {
+        // Folia start - region threading
+        io.papermc.paper.util.TickThread.ensureTickThread(world.getHandle(), position, "Cannot modify world asynchronously");
+        // Folia end - region threading
         this.requirePlaced();
         net.minecraft.world.item.ItemStack nms = org.bukkit.craftbukkit.inventory.CraftItemStack.asNMSCopy(item);
 
diff --git a/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java b/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java
index 3e93a6c489972ff2b4ecff3d83cc72b2d5c970f8..66dc7e20544c7000f4824b02cc3a31bc5c87f74c 100644
--- a/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java
+++ b/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java
@@ -50,7 +50,7 @@ public class ConsoleCommandCompleter implements Completer {
                         return syncEvent.callEvent() ? syncEvent.getCompletions() : com.google.common.collect.ImmutableList.of();
                     }
                 };
-                server.getServer().processQueue.add(syncCompletions);
+                io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(syncCompletions); // Folia - region threading
                 try {
                     final List<String> legacyCompletions = syncCompletions.get();
                     completions.removeIf(it -> !legacyCompletions.contains(it.suggestion())); // remove any suggestions that were removed
@@ -98,7 +98,7 @@ public class ConsoleCommandCompleter implements Completer {
                 return tabEvent.isCancelled() ? Collections.EMPTY_LIST : tabEvent.getCompletions();
             }
         };
-        server.getServer().processQueue.add(waitable); // Paper - Remove "this."
+        io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(waitable); // Folia - region threading
         try {
             List<String> offers = waitable.get();
             if (offers == null) {
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index e8e4489bcd64fde1b3226bdc7a7cc612508bda3f..1cfe604573000fa9b32237313aa467875a891f3c 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -234,6 +234,11 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
 
     @Override
     public boolean teleport(Location location, TeleportCause cause, io.papermc.paper.entity.TeleportFlag... flags) {
+        // Folia start - region threading
+        if (true) {
+            throw new UnsupportedOperationException("Must use teleportAsync while in region threading");
+        }
+        // Folia end - region threading
         // Paper end
         Preconditions.checkArgument(location != null, "location cannot be null");
         location.checkFinite();
@@ -700,7 +705,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         ImmutableSet.Builder<Player> players = ImmutableSet.builder();
 
         ServerLevel world = ((CraftWorld) this.getWorld()).getHandle();
-        ChunkMap.TrackedEntity entityTracker = world.getChunkSource().chunkMap.entityMap.get(this.getEntityId());
+        ChunkMap.TrackedEntity entityTracker = this.getHandle().tracker; // Folia - region threading
 
         if (entityTracker != null) {
             for (ServerPlayerConnection connection : entityTracker.seenBy) {
@@ -994,7 +999,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         }
 
         ServerLevel world = ((CraftWorld) this.getWorld()).getHandle();
-        ChunkMap.TrackedEntity entityTracker = world.getChunkSource().chunkMap.entityMap.get(this.getEntityId());
+        ChunkMap.TrackedEntity entityTracker = this.getHandle().tracker; // Folia - region threading
 
         if (entityTracker == null) {
             return;
@@ -1032,29 +1037,43 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         location.checkFinite();
         Location locationClone = location.clone(); // clone so we don't need to worry about mutations after this call.
 
-        net.minecraft.server.level.ServerLevel world = ((CraftWorld)locationClone.getWorld()).getHandle();
+        // Folia start - region threading
         java.util.concurrent.CompletableFuture<Boolean> ret = new java.util.concurrent.CompletableFuture<>();
-
-        world.loadChunksForMoveAsync(getHandle().getBoundingBoxAt(locationClone.getX(), locationClone.getY(), locationClone.getZ()),
-            this instanceof CraftPlayer ? ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER : ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL, (list) -> {
-                net.minecraft.server.level.ServerChunkCache chunkProviderServer = world.getChunkSource();
-                for (net.minecraft.world.level.chunk.ChunkAccess chunk : list) {
-                    chunkProviderServer.addTicketAtLevel(net.minecraft.server.level.TicketType.POST_TELEPORT, chunk.getPos(), 33, CraftEntity.this.getEntityId());
+        java.util.function.Consumer<Entity> run = (Entity nmsEntity) -> {
+            boolean success = nmsEntity.teleportAsync(
+                ((CraftWorld)locationClone.getWorld()).getHandle(),
+                new net.minecraft.world.phys.Vec3(locationClone.getX(), locationClone.getY(), locationClone.getZ()),
+                locationClone.getYaw(), locationClone.getPitch(), net.minecraft.world.phys.Vec3.ZERO,
+                cause == null ? TeleportCause.UNKNOWN : cause,
+                Entity.TELEPORT_FLAG_LOAD_CHUNK | Entity.TELEPORT_FLAG_TELEPORT_PASSENGERS, // preserve behavior with old API: dismount the entity so it can teleport
+                (Entity entityTp) -> {
+                    ret.complete(Boolean.TRUE);
                 }
-                net.minecraft.server.MinecraftServer.getServer().scheduleOnMain(() -> {
-                    try {
-                        ret.complete(CraftEntity.this.teleport(locationClone, cause, teleportFlags) ? Boolean.TRUE : Boolean.FALSE);
-                    } catch (Throwable throwable) {
-                        if (throwable instanceof ThreadDeath) {
-                            throw (ThreadDeath)throwable;
-                        }
-                        net.minecraft.server.MinecraftServer.LOGGER.error("Failed to teleport entity " + CraftEntity.this, throwable);
-                        ret.completeExceptionally(throwable);
-                    }
-                });
-            });
+            );
+            if (!success) {
+                ret.complete(Boolean.FALSE);
+            }
+        };
+        if (org.bukkit.Bukkit.isOwnedByCurrentRegion(this)) {
+            run.accept(this.getHandle());
+            return ret;
+        }
+        boolean scheduled = this.taskScheduler.schedule(
+            // success
+            run,
+            // retired
+            (Entity nmsEntity) -> {
+                ret.complete(Boolean.FALSE);
+            },
+            1L
+        );
+
+        if (!scheduled) {
+            ret.complete(Boolean.FALSE);
+        }
 
         return ret;
+        // Folia end - region threading
     }
     // Paper end - more teleport API / async chunk API
 
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 44f4665db613c558078df5bb49106e4ca5679dfe..232490c970d67e6bc77a35d5ccfef8fa95646ffe 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -562,7 +562,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
     @Override
     public void kickPlayer(String message) {
-        org.spigotmc.AsyncCatcher.catchOp("player kick"); // Spigot
+        //org.spigotmc.AsyncCatcher.catchOp("player kick"); // Spigot // Folia - thread-safe now, as it will simply delay the kick
         if (this.getHandle().connection == null) return;
 
         this.getHandle().connection.disconnect(message == null ? "" : message, org.bukkit.event.player.PlayerKickEvent.Cause.PLUGIN); // Paper - kick event cause
@@ -1309,6 +1309,11 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
     @Override
     public boolean teleport(Location location, org.bukkit.event.player.PlayerTeleportEvent.TeleportCause cause, io.papermc.paper.entity.TeleportFlag... flags) {
+        // Folia start - region threading
+        if (true) {
+            throw new UnsupportedOperationException("Must use teleportAsync while in region threading");
+        }
+        // Folia end - region threading
         Set<io.papermc.paper.entity.TeleportFlag.Relative> relativeArguments;
         Set<io.papermc.paper.entity.TeleportFlag> allFlags;
         if (flags.length == 0) {
@@ -1955,7 +1960,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
     private void unregisterEntity(Entity other) {
         // Paper end
         ChunkMap tracker = ((ServerLevel) this.getHandle().level()).getChunkSource().chunkMap;
-        ChunkMap.TrackedEntity entry = tracker.entityMap.get(other.getId());
+        ChunkMap.TrackedEntity entry = other.tracker; // Folia - region threading
         if (entry != null) {
             entry.removePlayer(this.getHandle());
         }
@@ -2052,7 +2057,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
             if (original != null) otherPlayer.setUUID(original); // Paper - uuid override
         }
 
-        ChunkMap.TrackedEntity entry = tracker.entityMap.get(other.getId());
+        ChunkMap.TrackedEntity entry = other.tracker; // Folia - region threading
         if (entry != null && !entry.seenBy.contains(this.getHandle().connection)) {
             entry.updatePlayer(this.getHandle());
         }
diff --git a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
index c0823c612de9dc2a64cc797f061eef25c5f31359..ccab0ec21a6827475d97654f1b54c166ccb99085 100644
--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
@@ -943,7 +943,7 @@ public class CraftEventFactory {
         return CraftEventFactory.handleBlockSpreadEvent(world, source, target, block, 2);
     }
 
-    public static BlockPos sourceBlockOverride = null; // SPIGOT-7068: Add source block override, not the most elegant way but better than passing down a BlockPosition up to five methods deep.
+    public static final ThreadLocal<BlockPos> sourceBlockOverrideRT = new ThreadLocal<>(); // SPIGOT-7068: Add source block override, not the most elegant way but better than passing down a BlockPosition up to five methods deep. // Folia - region threading
 
     public static boolean handleBlockSpreadEvent(LevelAccessor world, BlockPos source, BlockPos target, net.minecraft.world.level.block.state.BlockState block, int flag) {
         // Suppress during worldgen
@@ -955,7 +955,7 @@ public class CraftEventFactory {
         CraftBlockState state = CraftBlockStates.getBlockState(world, target, flag);
         state.setData(block);
 
-        BlockSpreadEvent event = new BlockSpreadEvent(state.getBlock(), CraftBlock.at(world, CraftEventFactory.sourceBlockOverride != null ? CraftEventFactory.sourceBlockOverride : source), state);
+        BlockSpreadEvent event = new BlockSpreadEvent(state.getBlock(), CraftBlock.at(world, CraftEventFactory.sourceBlockOverrideRT.get() != null ? CraftEventFactory.sourceBlockOverrideRT.get() : source), state); // Folia - region threading
         Bukkit.getPluginManager().callEvent(event);
 
         if (!event.isCancelled()) {
@@ -2146,7 +2146,7 @@ public class CraftEventFactory {
         CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemStack.copyWithCount(1));
 
         org.bukkit.event.block.BlockDispenseEvent event = new org.bukkit.event.block.BlockDispenseEvent(bukkitBlock, craftItem.clone(), CraftVector.toBukkit(to));
-        if (!net.minecraft.world.level.block.DispenserBlock.eventFired) {
+        if (!net.minecraft.world.level.block.DispenserBlock.eventFired.get().booleanValue()) { // Folia - region threading
             if (!event.callEvent()) {
                 return itemStack;
             }
diff --git a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
index e85b9bb3f9c225d289a4959921970b9963881199..b00e3b9b628f3d2a2fdbf1d2c77904963c16d3ac 100644
--- a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
+++ b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
@@ -532,6 +532,7 @@ public class CraftScheduler implements BukkitScheduler {
     }
 
     protected CraftTask handle(final CraftTask task, final long delay) { // Paper
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         // Paper start
         if (!this.isAsyncScheduler && !task.isSync()) {
             this.asyncScheduler.handle(task, delay);
diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
index 3c7a771c48cc2732cc038ca11bb93ec5f8c2d667..d365e26799822f39af2d5a27761bb8b41308297e 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
@@ -382,6 +382,12 @@ public final class CraftMagicNumbers implements UnsafeValues {
         String minimumVersion = MinecraftServer.getServer().server.minimumAPI;
         int minimumIndex = CraftMagicNumbers.SUPPORTED_API.indexOf(minimumVersion);
 
+        // Folia start - block plugins not marked as supported
+        if (!pdf.isFoliaSupported()) {
+            throw new InvalidPluginException("Plugin " + pdf.getFullName() + " is not marked as supporting regionised multithreading");
+        }
+        // Folia end - block plugins not marked as supported
+
         if (pdf.getAPIVersion() != null) {
             int pluginIndex = CraftMagicNumbers.SUPPORTED_API.indexOf(pdf.getAPIVersion());
 
diff --git a/src/main/java/org/bukkit/craftbukkit/util/DelegatedGeneratorAccess.java b/src/main/java/org/bukkit/craftbukkit/util/DelegatedGeneratorAccess.java
index 86a20c91beff6b27e6ec886e49ba902b216106f2..96007426144b78f91c12614f04350855530cc70d 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/DelegatedGeneratorAccess.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/DelegatedGeneratorAccess.java
@@ -69,6 +69,13 @@ public abstract class DelegatedGeneratorAccess implements WorldGenLevel {
         this.handle = worldAccess;
     }
 
+    // Folia start - region threading
+    @Override
+    public net.minecraft.world.level.StructureManager structureManager() {
+        return this.handle.structureManager();
+    }
+    // Folia end - region threading
+
     public WorldGenLevel getHandle() {
         return this.handle;
     }
diff --git a/src/main/java/org/spigotmc/ActivationRange.java b/src/main/java/org/spigotmc/ActivationRange.java
index 3283ed99c35ffed6805567705e0518d9f84feedc..4fc4690d03fd5f39e019f16845954052210c7361 100644
--- a/src/main/java/org/spigotmc/ActivationRange.java
+++ b/src/main/java/org/spigotmc/ActivationRange.java
@@ -52,7 +52,7 @@ public class ActivationRange
         RAIDER,
         MISC;
 
-        AABB boundingBox = new AABB( 0, 0, 0, 0, 0, 0 );
+        // Folia - threaded regions - replaced by local variable
     }
     // Paper start
 
@@ -65,26 +65,27 @@ public class ActivationRange
 
     private static int checkInactiveWakeup(Entity entity) {
         Level world = entity.level();
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - threaded regions
         SpigotWorldConfig config = world.spigotConfig;
-        long inactiveFor = MinecraftServer.currentTick - entity.activatedTick;
+        long inactiveFor = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() - entity.activatedTick; // Folia - threaded regions
         if (entity.activationType == ActivationType.VILLAGER) {
-            if (inactiveFor > config.wakeUpInactiveVillagersEvery && world.wakeupInactiveRemainingVillagers > 0) {
-                world.wakeupInactiveRemainingVillagers--;
+            if (inactiveFor > config.wakeUpInactiveVillagersEvery && worldData.wakeupInactiveRemainingVillagers > 0) { // Folia - threaded regions
+                worldData.wakeupInactiveRemainingVillagers--; // Folia - threaded regions
                 return config.wakeUpInactiveVillagersFor;
             }
         } else if (entity.activationType == ActivationType.ANIMAL) {
-            if (inactiveFor > config.wakeUpInactiveAnimalsEvery && world.wakeupInactiveRemainingAnimals > 0) {
-                world.wakeupInactiveRemainingAnimals--;
+            if (inactiveFor > config.wakeUpInactiveAnimalsEvery && worldData.wakeupInactiveRemainingAnimals > 0) { // Folia - threaded regions
+                worldData.wakeupInactiveRemainingAnimals--; // Folia - threaded regions
                 return config.wakeUpInactiveAnimalsFor;
             }
         } else if (entity.activationType == ActivationType.FLYING_MONSTER) {
-            if (inactiveFor > config.wakeUpInactiveFlyingEvery && world.wakeupInactiveRemainingFlying > 0) {
-                world.wakeupInactiveRemainingFlying--;
+            if (inactiveFor > config.wakeUpInactiveFlyingEvery && worldData.wakeupInactiveRemainingFlying > 0) { // Folia - threaded regions
+                worldData.wakeupInactiveRemainingFlying--; // Folia - threaded regions
                 return config.wakeUpInactiveFlyingFor;
             }
         } else if (entity.activationType == ActivationType.MONSTER || entity.activationType == ActivationType.RAIDER) {
-            if (inactiveFor > config.wakeUpInactiveMonstersEvery && world.wakeupInactiveRemainingMonsters > 0) {
-                world.wakeupInactiveRemainingMonsters--;
+            if (inactiveFor > config.wakeUpInactiveMonstersEvery && worldData.wakeupInactiveRemainingMonsters > 0) { // Folia - threaded regions
+                worldData.wakeupInactiveRemainingMonsters--; // Folia - threaded regions
                 return config.wakeUpInactiveMonstersFor;
             }
         }
@@ -92,7 +93,7 @@ public class ActivationRange
     }
     // Paper end
 
-    static AABB maxBB = new AABB( 0, 0, 0, 0, 0, 0 );
+    // Folia - threaded regions - replaced by local variable
 
     /**
      * Initializes an entities type on construction to specify what group this
@@ -176,10 +177,11 @@ public class ActivationRange
         final int waterActivationRange = world.spigotConfig.waterActivationRange;
         final int flyingActivationRange = world.spigotConfig.flyingMonsterActivationRange;
         final int villagerActivationRange = world.spigotConfig.villagerActivationRange;
-        world.wakeupInactiveRemainingAnimals = Math.min(world.wakeupInactiveRemainingAnimals + 1, world.spigotConfig.wakeUpInactiveAnimals);
-        world.wakeupInactiveRemainingVillagers = Math.min(world.wakeupInactiveRemainingVillagers + 1, world.spigotConfig.wakeUpInactiveVillagers);
-        world.wakeupInactiveRemainingMonsters = Math.min(world.wakeupInactiveRemainingMonsters + 1, world.spigotConfig.wakeUpInactiveMonsters);
-        world.wakeupInactiveRemainingFlying = Math.min(world.wakeupInactiveRemainingFlying + 1, world.spigotConfig.wakeUpInactiveFlying);
+        io.papermc.paper.threadedregions.RegionizedWorldData worldData = world.getCurrentWorldData(); // Folia - threaded regions
+        worldData.wakeupInactiveRemainingAnimals = Math.min(worldData.wakeupInactiveRemainingAnimals + 1, world.spigotConfig.wakeUpInactiveAnimals); // Folia - threaded regions
+        worldData.wakeupInactiveRemainingVillagers = Math.min(worldData.wakeupInactiveRemainingVillagers + 1, world.spigotConfig.wakeUpInactiveVillagers); // Folia - threaded regions
+        worldData.wakeupInactiveRemainingMonsters = Math.min(worldData.wakeupInactiveRemainingMonsters + 1, world.spigotConfig.wakeUpInactiveMonsters); // Folia - threaded regions
+        worldData.wakeupInactiveRemainingFlying = Math.min(worldData.wakeupInactiveRemainingFlying + 1, world.spigotConfig.wakeUpInactiveFlying); // Folia - threaded regions
         final ServerChunkCache chunkProvider = (ServerChunkCache) world.getChunkSource();
         // Paper end
 
@@ -193,9 +195,9 @@ public class ActivationRange
         // Paper end
         maxRange = Math.min( ( world.spigotConfig.simulationDistance << 4 ) - 8, maxRange );
 
-        for ( Player player : world.players() )
+        for ( Player player : world.getLocalPlayers() ) // Folia - region threading
         {
-            player.activatedTick = MinecraftServer.currentTick;
+            player.activatedTick = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick(); // Folia - region threading
             if ( world.spigotConfig.ignoreSpectatorActivation && player.isSpectator() )
             {
                 continue;
@@ -203,26 +205,33 @@ public class ActivationRange
 
             // Paper start
             int worldHeight = world.getHeight();
-            ActivationRange.maxBB = player.getBoundingBox().inflate( maxRange, worldHeight, maxRange );
-            ActivationType.MISC.boundingBox = player.getBoundingBox().inflate( miscActivationRange, worldHeight, miscActivationRange );
-            ActivationType.RAIDER.boundingBox = player.getBoundingBox().inflate( raiderActivationRange, worldHeight, raiderActivationRange );
-            ActivationType.ANIMAL.boundingBox = player.getBoundingBox().inflate( animalActivationRange, worldHeight, animalActivationRange );
-            ActivationType.MONSTER.boundingBox = player.getBoundingBox().inflate( monsterActivationRange, worldHeight, monsterActivationRange );
-            ActivationType.WATER.boundingBox = player.getBoundingBox().inflate( waterActivationRange, worldHeight, waterActivationRange );
-            ActivationType.FLYING_MONSTER.boundingBox = player.getBoundingBox().inflate( flyingActivationRange, worldHeight, flyingActivationRange );
-            ActivationType.VILLAGER.boundingBox = player.getBoundingBox().inflate( villagerActivationRange, worldHeight, villagerActivationRange );
+            AABB maxBB = player.getBoundingBox().inflate( maxRange, worldHeight, maxRange ); // Folia - threaded regions
+            AABB[] bbByType = new AABB[ActivationType.values().length];
+            bbByType[ActivationType.MISC.ordinal()] = player.getBoundingBox().inflate( miscActivationRange, worldHeight, miscActivationRange ); // Folia - threaded regions
+            bbByType[ActivationType.RAIDER.ordinal()] =  player.getBoundingBox().inflate( raiderActivationRange, worldHeight, raiderActivationRange ); // Folia - threaded regions
+            bbByType[ActivationType.ANIMAL.ordinal()] =  player.getBoundingBox().inflate( animalActivationRange, worldHeight, animalActivationRange ); // Folia - threaded regions
+            bbByType[ActivationType.MONSTER.ordinal()] =  player.getBoundingBox().inflate( monsterActivationRange, worldHeight, monsterActivationRange ); // Folia - threaded regions
+            bbByType[ActivationType.WATER.ordinal()] =  player.getBoundingBox().inflate( waterActivationRange, worldHeight, waterActivationRange ); // Folia - threaded regions
+            bbByType[ActivationType.FLYING_MONSTER.ordinal()] =  player.getBoundingBox().inflate( flyingActivationRange, worldHeight, flyingActivationRange ); // Folia - threaded regions
+            bbByType[ActivationType.VILLAGER.ordinal()] =  player.getBoundingBox().inflate( villagerActivationRange, worldHeight, villagerActivationRange ); // Folia - threaded regions
             // Paper end
 
             // Paper start
-            java.util.List<Entity> entities = world.getEntities((Entity)null, ActivationRange.maxBB, null);
+            java.util.List<Entity> entities = new java.util.ArrayList<>(); // Folia - region ticking - bypass getEntities thread check, we perform a check on the entities later
+            ((net.minecraft.server.level.ServerLevel)world).getEntityLookup().getEntities((Entity)null, maxBB, entities, null); // Folia - region ticking - bypass getEntities thread check, we perform a check on the entities later
             boolean tickMarkers = world.paperConfig().entities.markers.tick; // Paper - Configurable marker ticking
             for (Entity entity : entities) {
                 // Paper start - Configurable marker ticking
+                // Folia start - region ticking
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(entity)) {
+                    continue;
+                }
+                // Folia end - region ticking
                 if (!tickMarkers && entity instanceof net.minecraft.world.entity.Marker) {
                     continue;
                 }
                 // Paper end - Configurable marker ticking
-                ActivationRange.activateEntity(entity);
+                ActivationRange.activateEntity(entity, bbByType); // Folia - threaded regions
             }
             // Paper end
         }
@@ -234,18 +243,18 @@ public class ActivationRange
      *
      * @param chunk
      */
-    private static void activateEntity(Entity entity)
+    private static void activateEntity(Entity entity, AABB[] bbByType) // Folia - threaded regions
     {
-        if ( MinecraftServer.currentTick > entity.activatedTick )
+        if ( io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() > entity.activatedTick ) // Folia - threaded regions
         {
             if ( entity.defaultActivationState )
             {
-                entity.activatedTick = MinecraftServer.currentTick;
+                entity.activatedTick = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick(); // Folia - threaded regions
                 return;
             }
-            if ( entity.activationType.boundingBox.intersects( entity.getBoundingBox() ) )
+            if ( bbByType[entity.activationType.ordinal()].intersects( entity.getBoundingBox() ) ) // Folia - threaded regions
             {
-                entity.activatedTick = MinecraftServer.currentTick;
+                entity.activatedTick = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick(); // Folia - threaded regions
             }
         }
     }
@@ -268,10 +277,10 @@ public class ActivationRange
         if (entity.getRemainingFireTicks() > 0) {
             return 2;
         }
-        if (entity.activatedImmunityTick >= MinecraftServer.currentTick) {
+        if (entity.activatedImmunityTick >= io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick()) { // Folia - threaded regions
             return 1;
         }
-        long inactiveFor = MinecraftServer.currentTick - entity.activatedTick;
+        long inactiveFor = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() - entity.activatedTick; // Folia - threaded regions
         // Paper end
         // quick checks.
         if ( (entity.activationType != ActivationType.WATER && entity.wasTouchingWater && entity.isPushedByFluid()) ) // Paper
@@ -394,19 +403,19 @@ public class ActivationRange
         }
         // Paper end
 
-        boolean isActive = entity.activatedTick >= MinecraftServer.currentTick;
+        boolean isActive = entity.activatedTick >= io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick(); // Folia - threaded regions
         entity.isTemporarilyActive = false; // Paper
 
         // Should this entity tick?
         if ( !isActive )
         {
-            if ( ( MinecraftServer.currentTick - entity.activatedTick - 1 ) % 20 == 0 )
+            if ( ( io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() - entity.activatedTick - 1 ) % 20 == 0 ) // Folia - threaded regions
             {
                 // Check immunities every 20 ticks.
                 // Paper start
                 int immunity = checkEntityImmunities(entity);
                 if (immunity >= 0) {
-                    entity.activatedTick = MinecraftServer.currentTick + immunity;
+                    entity.activatedTick = io.papermc.paper.threadedregions.RegionizedServer.getCurrentTick() + immunity; // Folia - threaded regions
                 } else {
                     entity.isTemporarilyActive = true;
                 }
diff --git a/src/main/java/org/spigotmc/SpigotCommand.java b/src/main/java/org/spigotmc/SpigotCommand.java
index ac0fd418fcb437896dfdff53ab3eff19833d25fb..130220977477a5d8d51e17dcb989ae0c858643cb 100644
--- a/src/main/java/org/spigotmc/SpigotCommand.java
+++ b/src/main/java/org/spigotmc/SpigotCommand.java
@@ -29,6 +29,7 @@ public class SpigotCommand extends Command {
             Command.broadcastCommandMessage(sender, ChatColor.RED + "Please note that this command is not supported and may cause issues.");
             Command.broadcastCommandMessage(sender, ChatColor.RED + "If you encounter any issues please use the /stop command to restart your server.");
 
+            io.papermc.paper.threadedregions.RegionizedServer.getInstance().addTask(() -> { // Folia - region threading
             MinecraftServer console = MinecraftServer.getServer();
             org.spigotmc.SpigotConfig.init((File) console.options.valueOf("spigot-settings"));
             for (ServerLevel world : console.getAllLevels()) {
@@ -37,6 +38,7 @@ public class SpigotCommand extends Command {
             console.server.reloadCount++;
 
             Command.broadcastCommandMessage(sender, ChatColor.GREEN + "Reload complete.");
+            }); // Folia - region threading
         }
 
         return true;
diff --git a/src/main/java/org/spigotmc/SpigotConfig.java b/src/main/java/org/spigotmc/SpigotConfig.java
index 6c260403d91d640da0473a3df56e1c5582459fde..f685fd53ef631b32b6c51dfc7f0d847ed2dc9658 100644
--- a/src/main/java/org/spigotmc/SpigotConfig.java
+++ b/src/main/java/org/spigotmc/SpigotConfig.java
@@ -228,7 +228,7 @@ public class SpigotConfig
         SpigotConfig.restartOnCrash = SpigotConfig.getBoolean( "settings.restart-on-crash", SpigotConfig.restartOnCrash );
         SpigotConfig.restartScript = SpigotConfig.getString( "settings.restart-script", SpigotConfig.restartScript );
         SpigotConfig.restartMessage = SpigotConfig.transform( SpigotConfig.getString( "messages.restart", "Server is restarting" ) );
-        SpigotConfig.commands.put( "restart", new RestartCommand( "restart" ) );
+        // SpigotConfig.commands.put( "restart", new RestartCommand( "restart" ) ); // Folia - region threading
         // WatchdogThread.doStart( SpigotConfig.timeoutTime, SpigotConfig.restartOnCrash ); // Paper - moved to after paper config initialization
     }
 
@@ -283,7 +283,7 @@ public class SpigotConfig
 
     private static void tpsCommand()
     {
-        SpigotConfig.commands.put( "tps", new TicksPerSecondCommand( "tps" ) );
+        //SpigotConfig.commands.put( "tps", new TicksPerSecondCommand( "tps" ) ); // Folia - region threading
     }
 
     public static int playerSample;
diff --git a/src/main/java/org/spigotmc/SpigotWorldConfig.java b/src/main/java/org/spigotmc/SpigotWorldConfig.java
index 1cf6d4f854d89c515e48e1fb365eb95ff9340765..efe5b848a8e3645cae10c435196c8189b7422f45 100644
--- a/src/main/java/org/spigotmc/SpigotWorldConfig.java
+++ b/src/main/java/org/spigotmc/SpigotWorldConfig.java
@@ -435,7 +435,7 @@ public class SpigotWorldConfig
         this.otherMultiplier = (float) this.getDouble( "hunger.other-multiplier", 0.0 );
     }
 
-    public int currentPrimedTnt = 0;
+    //public int currentPrimedTnt = 0; // Folia - region threading - moved to regionised world data
     public int maxTntTicksPerTick;
     private void maxTntPerTick() {
         if ( SpigotConfig.version < 7 )