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

Connection thread-safety fixes

- send packet
- pending addition

diff --git a/src/main/java/ca/spottedleaf/concurrentutil/collection/MultiThreadedQueue.java b/src/main/java/ca/spottedleaf/concurrentutil/collection/MultiThreadedQueue.java
index f4415f782b32fed25da98e44b172f717c4d46e34..ba7c24b3627a1827721d2462add15fdd4adbed90 100644
--- a/src/main/java/ca/spottedleaf/concurrentutil/collection/MultiThreadedQueue.java
+++ b/src/main/java/ca/spottedleaf/concurrentutil/collection/MultiThreadedQueue.java
@@ -392,6 +392,24 @@ public class MultiThreadedQueue<E> implements Queue<E> {
         }
     }
 
+    /**
+     * Returns whether this queue is currently add-blocked. That is, whether {@link #add(Object)} and friends will return {@code false}.
+     */
+    public boolean isAddBlocked() {
+        for (LinkedNode<E> tail = this.getTailOpaque();;) {
+            LinkedNode<E> next = tail.getNextVolatile();
+            if (next == null) {
+                return false;
+            }
+
+            if (next == tail) {
+                return true;
+            }
+
+            tail = next;
+        }
+    }
+
     /**
      * Atomically removes the head from this queue if it exists, otherwise prevents additions to this queue if no
      * head is removed.
diff --git a/src/main/java/ca/spottedleaf/concurrentutil/lock/ImproveReentrantLock.java b/src/main/java/ca/spottedleaf/concurrentutil/lock/ImproveReentrantLock.java
new file mode 100644
index 0000000000000000000000000000000000000000..9df9881396f4a69b51acaae562b12b8ce0a48443
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/concurrentutil/lock/ImproveReentrantLock.java
@@ -0,0 +1,139 @@
+package ca.spottedleaf.concurrentutil.lock;
+
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import java.lang.invoke.VarHandle;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.AbstractQueuedSynchronizer;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+
+/**
+ * Implementation of {@link Lock} that should outperform {@link java.util.concurrent.locks.ReentrantLock}.
+ * The lock is considered a non-fair lock, as specified by {@link java.util.concurrent.locks.ReentrantLock},
+ * and additionally does <i>not</i> support the creation of Conditions.
+ *
+ * <p>
+ * Specifically, this implementation is careful to avoid synchronisation penalties when multi-acquiring and
+ * multi-releasing locks from the same thread, and additionally avoids unnecessary synchronisation penalties
+ * when releasing the lock.
+ * </p>
+ */
+public class ImproveReentrantLock implements Lock {
+
+    private final InternalLock lock = new InternalLock();
+
+    private static final class InternalLock extends AbstractQueuedSynchronizer {
+
+        private volatile Thread owner;
+        private static final VarHandle OWNER_HANDLE = ConcurrentUtil.getVarHandle(InternalLock.class, "owner", Thread.class);
+        private int count;
+
+        private Thread getOwnerPlain() {
+            return (Thread)OWNER_HANDLE.get(this);
+        }
+
+        private Thread getOwnerVolatile() {
+            return (Thread)OWNER_HANDLE.getVolatile(this);
+        }
+
+        private void setOwnerRelease(final Thread to) {
+            OWNER_HANDLE.setRelease(this, to);
+        }
+
+        private void setOwnerVolatile(final Thread to) {
+            OWNER_HANDLE.setVolatile(this, to);
+        }
+
+        private Thread compareAndExchangeOwnerVolatile(final Thread expect, final Thread update) {
+            return (Thread)OWNER_HANDLE.compareAndExchange(this, expect, update);
+        }
+
+        @Override
+        protected final boolean tryAcquire(int acquires) {
+            final Thread current = Thread.currentThread();
+            final Thread owner = this.getOwnerVolatile();
+
+            // When trying to blind acquire the lock, using just compare and exchange is faster
+            // than reading the owner field first - but comes at the cost of performing the compare and exchange
+            // even if the current thread owns the lock
+            if ((owner == null && null == this.compareAndExchangeOwnerVolatile(null, current)) || owner == current) {
+                this.count += acquires;
+                return true;
+            }
+
+            return false;
+        }
+
+        @Override
+        protected final boolean tryRelease(int releases) {
+            if (this.getOwnerPlain() == Thread.currentThread()) {
+                final int newCount = this.count -= releases;
+                if (newCount == 0) {
+                    // When the caller, which is release(), attempts to signal the next node, it will use volatile
+                    // to retrieve the node and status.
+                    // Let's say that we have written this field null as release, and then checked for a next node
+                    // using volatile and then determined there are no waiters.
+                    // While a call to tryAcquire() can fail for another thread since the write may not
+                    // publish yet, once the thread adds itself to the waiters list it will synchronise with
+                    // the write to the field, since the volatile write to put the thread on the waiter list
+                    // will synchronise with the volatile read we did earlier to check for any
+                    // waiters.
+                    this.setOwnerRelease(null);
+                    return true;
+                }
+                return false;
+            }
+            throw new IllegalMonitorStateException();
+        }
+    }
+
+    /**
+     * Returns the thread that owns the lock, or returns {@code null} if there is no such thread.
+     */
+    public Thread getLockOwner() {
+        return this.lock.getOwnerVolatile();
+    }
+
+    /**
+     * Returns whether the current thread owns the lock.
+     */
+    public boolean isHeldByCurrentThread() {
+        return this.lock.getOwnerPlain() == Thread.currentThread();
+    }
+
+    @Override
+    public void lock() {
+        this.lock.acquire(1);
+    }
+
+    @Override
+    public void lockInterruptibly() throws InterruptedException {
+        if (Thread.interrupted()) {
+            throw new InterruptedException();
+        }
+        this.lock.acquireInterruptibly(1);
+    }
+
+    @Override
+    public boolean tryLock() {
+        return this.lock.tryAcquire(1);
+    }
+
+    @Override
+    public boolean tryLock(final long time, final TimeUnit unit) throws InterruptedException {
+        if (Thread.interrupted()) {
+            throw new InterruptedException();
+        }
+        return this.lock.tryAcquire(1) || this.lock.tryAcquireNanos(1, unit.toNanos(time));
+    }
+
+    @Override
+    public void unlock() {
+        this.lock.release(1);
+    }
+
+    @Override
+    public Condition newCondition() {
+        throw new UnsupportedOperationException();
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/concurrentutil/lock/RBLock.java b/src/main/java/ca/spottedleaf/concurrentutil/lock/RBLock.java
new file mode 100644
index 0000000000000000000000000000000000000000..793a7326141b7d83395585b3d32b0a7e8a6238a7
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/concurrentutil/lock/RBLock.java
@@ -0,0 +1,303 @@
+package ca.spottedleaf.concurrentutil.lock;
+
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import java.lang.invoke.VarHandle;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.LockSupport;
+
+// ReentrantBiasedLock
+public final class RBLock implements Lock {
+
+    private volatile LockWaiter owner;
+    private static final VarHandle OWNER_HANDLE = ConcurrentUtil.getVarHandle(RBLock.class, "owner", LockWaiter.class);
+
+    private volatile LockWaiter tail;
+    private static final VarHandle TAIL_HANDLE = ConcurrentUtil.getVarHandle(RBLock.class, "tail", LockWaiter.class);
+
+    public RBLock() {
+        // we can have the initial state as if it was locked by this thread, then unlocked
+        final LockWaiter dummy = new LockWaiter(null, LockWaiter.STATE_BIASED, null);
+        this.setOwnerPlain(dummy);
+        // release ensures correct publishing
+        this.setTailRelease(dummy);
+    }
+
+    private LockWaiter getOwnerVolatile() {
+        return (LockWaiter)OWNER_HANDLE.getVolatile(this);
+    }
+
+    private void setOwnerPlain(final LockWaiter value) {
+        OWNER_HANDLE.set(this, value);
+    }
+
+    private void setOwnerRelease(final LockWaiter value) {
+        OWNER_HANDLE.setRelease(this, value);
+    }
+
+
+
+    private void setTailOpaque(final LockWaiter newTail) {
+        TAIL_HANDLE.setOpaque(this, newTail);
+    }
+
+    private void setTailRelease(final LockWaiter newTail) {
+        TAIL_HANDLE.setRelease(this, newTail);
+    }
+
+    private LockWaiter getTailOpaque() {
+        return (LockWaiter)TAIL_HANDLE.getOpaque(this);
+    }
+
+
+    private void appendWaiter(final LockWaiter waiter) {
+        // Similar to MultiThreadedQueue#appendList
+        int failures = 0;
+
+        for (LockWaiter currTail = this.getTailOpaque(), curr = currTail;;) {
+            /* It has been experimentally shown that placing the read before the backoff results in significantly greater performance */
+            /* It is likely due to a cache miss caused by another write to the next field */
+            final LockWaiter next = curr.getNextVolatile();
+
+            for (int i = 0; i < failures; ++i) {
+                Thread.onSpinWait();
+            }
+
+            if (next == null) {
+                final LockWaiter compared = curr.compareAndExchangeNextVolatile(null, waiter);
+
+                if (compared == null) {
+                    /* Added */
+                    /* Avoid CASing on tail more than we need to */
+                    /* CAS to avoid setting an out-of-date tail */
+                    if (this.getTailOpaque() == currTail) {
+                        this.setTailOpaque(waiter);
+                    }
+                    return;
+                }
+
+                ++failures;
+                curr = compared;
+                continue;
+            }
+
+            if (curr == currTail) {
+                /* Tail is likely not up-to-date */
+                curr = next;
+            } else {
+                /* Try to update to tail */
+                if (currTail == (currTail = this.getTailOpaque())) {
+                    curr = next;
+                } else {
+                    curr = currTail;
+                }
+            }
+        }
+    }
+
+    // required that expected is already appended to the wait chain
+    private boolean tryAcquireBiased(final LockWaiter expected) {
+        final LockWaiter owner = this.getOwnerVolatile();
+        if (owner.getNextVolatile() == expected && owner.getStateVolatile() == LockWaiter.STATE_BIASED) {
+            this.setOwnerRelease(expected);
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    public void lock() {
+        final Thread currThread = Thread.currentThread();
+        final LockWaiter owner = this.getOwnerVolatile();
+
+        // try to fast acquire
+
+        final LockWaiter acquireObj;
+        boolean needAppend = true;
+
+        if (owner.getNextVolatile() != null) {
+            // unlikely we are able to fast acquire
+            acquireObj = new LockWaiter(currThread, 1, null);
+        } else {
+            // may be able to fast acquire the lock
+            if (owner.owner == currThread) {
+                final int oldState = owner.incrementState();
+                if (oldState == LockWaiter.STATE_BIASED) {
+                    // in this case, we may not have the lock.
+                    final LockWaiter next = owner.getNextVolatile();
+                    if (next == null) {
+                        // we win the lock
+                        return;
+                    } else {
+                        // we have incremented the state, which means any tryAcquireBiased() will fail.
+                        // The next waiter may be waiting for us, so we need to re-set our state and then
+                        // try to push the lock to them.
+                        // We cannot simply claim ownership of the lock, since we don't know if the next waiter saw
+                        // the biased state
+                        owner.setStateRelease(LockWaiter.STATE_BIASED);
+                        LockSupport.unpark(next.owner);
+
+                        acquireObj = new LockWaiter(currThread, 1, null);
+                        // fall through to slower lock logic
+                    }
+                } else {
+                    // we already have the lock
+                    return;
+                }
+            } else {
+                acquireObj = new LockWaiter(currThread, 1, null);
+                if (owner.getStateVolatile() == LockWaiter.STATE_BIASED) {
+                    // we may be able to quickly acquire the lock
+                    if (owner.getNextVolatile() == null && null == owner.compareAndExchangeNextVolatile(null, acquireObj)) {
+                        if (owner.getStateVolatile() == LockWaiter.STATE_BIASED) {
+                            this.setOwnerRelease(acquireObj);
+                            return;
+                        } else {
+                            needAppend = false;
+                            // we failed to acquire, but we can block instead - we did CAS to the next immediate owner
+                        }
+                    }
+                } // else: fall through to append and wait code
+            }
+        }
+
+        if (needAppend) {
+            this.appendWaiter(acquireObj); // append to end of waiters
+        }
+
+        // failed to fast acquire, so now we may need to block
+        final int spinAttempts = 10;
+        for (int i = 0; i < spinAttempts; ++i) {
+            for (int k = 0; k <= i; ++i) {
+                Thread.onSpinWait();
+            }
+            if (this.tryAcquireBiased(acquireObj)) {
+                // acquired
+                return;
+            }
+        }
+
+        // slow acquire
+        while (!this.tryAcquireBiased(acquireObj)) {
+            LockSupport.park(this);
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     * @throws IllegalMonitorStateException If the current thread does not own the lock.
+     */
+    @Override
+    public void unlock() {
+        final LockWaiter owner = this.getOwnerVolatile();
+
+        final int oldState;
+        if (owner.owner != Thread.currentThread() || (oldState = owner.getStatePlain()) <= 0) {
+            throw new IllegalMonitorStateException();
+        }
+
+        owner.setStateRelease(oldState - 1);
+
+        if (oldState != 1) {
+            return;
+        }
+
+        final LockWaiter next = owner.getNextVolatile();
+
+        if (next == null) {
+            // we can leave the lock in biased state, which will save a CAS
+            return;
+        }
+
+        // we have TWO cases:
+        // waiter saw the lock in biased state
+        // waiter did not see the lock in biased state
+        // the problem is that if the waiter saw the lock in the biased state, then it now owns the lock. but if it did not,
+        // then we still own the lock.
+
+        // However, by unparking always, the waiter will try to acquire the biased lock from us.
+        LockSupport.unpark(next.owner);
+    }
+
+    @Override
+    public void lockInterruptibly() throws InterruptedException {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean tryLock() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public Condition newCondition() {
+        throw new UnsupportedOperationException();
+    }
+
+    static final class LockWaiter {
+
+        static final int STATE_BIASED = 0;
+
+        private volatile LockWaiter next;
+        private volatile int state;
+        private Thread owner;
+
+        private static final VarHandle NEXT_HANDLE = ConcurrentUtil.getVarHandle(LockWaiter.class, "next", LockWaiter.class);
+        private static final VarHandle STATE_HANDLE = ConcurrentUtil.getVarHandle(LockWaiter.class, "state", int.class);
+
+
+        private LockWaiter compareAndExchangeNextVolatile(final LockWaiter expect, final LockWaiter update) {
+            return (LockWaiter)NEXT_HANDLE.compareAndExchange((LockWaiter)this, expect, update);
+        }
+
+        private void setNextPlain(final LockWaiter next) {
+            NEXT_HANDLE.set((LockWaiter)this, next);
+        }
+
+        private LockWaiter getNextOpaque() {
+            return (LockWaiter)NEXT_HANDLE.getOpaque((LockWaiter)this);
+        }
+
+        private LockWaiter getNextVolatile() {
+            return (LockWaiter)NEXT_HANDLE.getVolatile((LockWaiter)this);
+        }
+
+
+
+        private int getStatePlain() {
+            return (int)STATE_HANDLE.get((LockWaiter)this);
+        }
+
+        private int getStateVolatile() {
+            return (int)STATE_HANDLE.getVolatile((LockWaiter)this);
+        }
+
+        private void setStatePlain(final int value) {
+            STATE_HANDLE.set((LockWaiter)this, value);
+        }
+
+        private void setStateRelease(final int value) {
+            STATE_HANDLE.setRelease((LockWaiter)this, value);
+        }
+
+        public LockWaiter(final Thread owner, final int initialState, final LockWaiter next) {
+            this.owner = owner;
+            this.setStatePlain(initialState);
+            this.setNextPlain(next);
+        }
+
+        public int incrementState() {
+            final int old = this.getStatePlain();
+            // Technically, we DO NOT need release for old != BIASED. But we care about optimising only for x86,
+            // which is a simple MOV for everything but volatile.
+            this.setStateRelease(old + 1);
+            return old;
+        }
+    }
+}
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 1e98f778ffa0a7bb00ebccaaa8bde075183e41f0..aebe82cbe8bc20e5f4260a871d7b620e5092b2c9 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..f579ad58ea7db20d6d7b89abbab3a4dfadaaeaee
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/concurrentutil/scheduler/SchedulerThreadPool.java
@@ -0,0 +1,534 @@
+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.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;
+    }
+
+    /**
+     * 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/ca/spottedleaf/leafprofiler/LProfileGraph.java b/src/main/java/ca/spottedleaf/leafprofiler/LProfileGraph.java
new file mode 100644
index 0000000000000000000000000000000000000000..14a4778f7913b849fabbd772f9cb8a0bc5a6ed6c
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/leafprofiler/LProfileGraph.java
@@ -0,0 +1,58 @@
+package ca.spottedleaf.leafprofiler;
+
+import ca.spottedleaf.concurrentutil.map.SWMRInt2IntHashTable;
+import java.util.Arrays;
+
+public final class LProfileGraph {
+
+    public static final int ROOT_NODE = 0;
+
+    // volatile required for correct publishing after resizing
+    private volatile SWMRInt2IntHashTable[] nodes = new SWMRInt2IntHashTable[16];
+    private int nodeCount;
+
+    public LProfileGraph() {
+        this.nodes[ROOT_NODE] = new SWMRInt2IntHashTable();
+        this.nodeCount = 1;
+    }
+
+    private int createNode(final int parent, final int type) {
+        synchronized (this) {
+            SWMRInt2IntHashTable[] nodes = this.nodes;
+
+            final SWMRInt2IntHashTable node = nodes[parent];
+
+            final int newNode = this.nodeCount;
+            final int prev = node.putIfAbsent(type, newNode);
+
+            if (prev != 0) {
+                // already exists
+                return prev;
+            }
+
+            // insert new node
+            ++this.nodeCount;
+
+            if (newNode >= nodes.length) {
+                this.nodes = nodes = Arrays.copyOf(nodes, nodes.length * 2);
+            }
+
+            nodes[newNode] = new SWMRInt2IntHashTable();
+
+            return newNode;
+        }
+    }
+
+    public int getOrCreateNode(final int parent, final int type) {
+        // note: requires parent node to exist
+        final SWMRInt2IntHashTable[] nodes = this.nodes;
+
+        final int mapping = nodes[parent].get(type);
+
+        if (mapping != 0) {
+            return mapping;
+        }
+
+        return this.createNode(parent, type);
+    }
+}
diff --git a/src/main/java/ca/spottedleaf/leafprofiler/LProfilerRegistry.java b/src/main/java/ca/spottedleaf/leafprofiler/LProfilerRegistry.java
new file mode 100644
index 0000000000000000000000000000000000000000..ffa32c1eae22bda371dd1d0318cc7c587f8e5a5c
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/leafprofiler/LProfilerRegistry.java
@@ -0,0 +1,59 @@
+package ca.spottedleaf.leafprofiler;
+
+import java.util.Arrays;
+import java.util.concurrent.ConcurrentHashMap;
+
+public final class LProfilerRegistry {
+
+    // volatile required to ensure correct publishing when resizing
+    private volatile ProfilerEntry[] typesById = new ProfilerEntry[16];
+    private int totalEntries;
+    private final ConcurrentHashMap<String, ProfilerEntry> nameToEntry = new ConcurrentHashMap<>();
+
+    public LProfilerRegistry() {
+
+    }
+
+    public ProfilerEntry getById(final int id) {
+        final ProfilerEntry[] entries = this.typesById;
+
+        return id < 0 || id >= entries.length ? null : entries[id];
+    }
+
+    public ProfilerEntry getByName(final String name) {
+        return this.nameToEntry.get(name);
+    }
+
+    public int createType(final ProfileType type, final String name) {
+        synchronized (this) {
+            final int id = this.totalEntries;
+
+            final ProfilerEntry ret = new ProfilerEntry(type, name, id);
+
+            final ProfilerEntry prev = this.nameToEntry.putIfAbsent(name, ret);
+
+            if (prev != null) {
+                throw new IllegalStateException("Entry already exists: " + prev);
+            }
+
+            ++this.totalEntries;
+
+            ProfilerEntry[] entries = this.typesById;
+
+            if (id >= entries.length) {
+                this.typesById = entries = Arrays.copyOf(entries, entries.length * 2);
+            }
+
+            // should be opaque, but I don't think that matters here.
+            entries[id] = ret;
+
+            return id;
+        }
+    }
+
+    public static enum ProfileType {
+        TIMER, COUNTER
+    }
+
+    public static record ProfilerEntry(ProfileType type, String name, int id) {}
+}
diff --git a/src/main/java/ca/spottedleaf/leafprofiler/LeafProfiler.java b/src/main/java/ca/spottedleaf/leafprofiler/LeafProfiler.java
new file mode 100644
index 0000000000000000000000000000000000000000..ad8c590fe7479fcb3c7ff5dc3ac3a4d6f33c5938
--- /dev/null
+++ b/src/main/java/ca/spottedleaf/leafprofiler/LeafProfiler.java
@@ -0,0 +1,61 @@
+package ca.spottedleaf.leafprofiler;
+
+import it.unimi.dsi.fastutil.ints.IntArrayFIFOQueue;
+import it.unimi.dsi.fastutil.longs.LongArrayFIFOQueue;
+import java.util.Arrays;
+
+public final class LeafProfiler {
+
+    public final LProfilerRegistry registry;
+    public final LProfileGraph graph;
+
+    private long[] data;
+    private final IntArrayFIFOQueue callStack = new IntArrayFIFOQueue();
+    private int topOfStack = LProfileGraph.ROOT_NODE;
+    private final LongArrayFIFOQueue timerStack = new LongArrayFIFOQueue();
+    private long lastTimerStart = 0L;
+
+    public LeafProfiler(final LProfilerRegistry registry, final LProfileGraph graph) {
+        this.registry = registry;
+        this.graph = graph;
+    }
+
+    private long[] resizeData(final long[] old, final int least) {
+        return this.data = Arrays.copyOf(old, Math.max(old.length * 2, least * 2));
+    }
+
+    private void incrementDirect(final int nodeId, final long count) {
+        final long[] data = this.data;
+        if (nodeId >= data.length) {
+            this.resizeData(data, nodeId)[nodeId] += count;
+        } else {
+            data[nodeId] += count;
+        }
+    }
+
+    public void incrementCounter(final int type, final long count) {
+        // this is supposed to be an optimised version of startTimer then stopTimer
+        final int node = this.graph.getOrCreateNode(this.topOfStack, type);
+        this.incrementDirect(node, count);
+    }
+
+    public void startTimer(final int type, final long startTime) {
+        final int parentNode = this.topOfStack;
+        final int newNode = this.graph.getOrCreateNode(parentNode, type);
+        this.callStack.enqueue(parentNode);
+        this.topOfStack = newNode;
+
+        this.timerStack.enqueue(this.lastTimerStart);
+        this.lastTimerStart = startTime;
+    }
+
+    public void stopTimer(final int type, final long endTime) {
+        final int currentNode = this.topOfStack;
+        this.topOfStack = this.callStack.dequeueLastInt();
+
+        final long lastStart = this.lastTimerStart;
+        this.lastTimerStart = this.timerStack.dequeueLastLong();
+
+        this.incrementDirect(currentNode, endTime - lastStart);
+    }
+}
diff --git a/src/main/java/com/destroystokyo/paper/Metrics.java b/src/main/java/com/destroystokyo/paper/Metrics.java
index 4b002e8b75d117b726b0de274a76d3596fce015b..897cb94abf7b53da8ba7cda5135b6580aa2d9824 100644
--- a/src/main/java/com/destroystokyo/paper/Metrics.java
+++ b/src/main/java/com/destroystokyo/paper/Metrics.java
@@ -593,7 +593,7 @@ public class Metrics {
             boolean logFailedRequests = config.getBoolean("logFailedRequests", false);
             // Only start Metrics, if it's enabled in the config
             if (config.getBoolean("enabled", true)) {
-                Metrics metrics = new Metrics("Paper", serverUUID, logFailedRequests, Bukkit.getLogger());
+                Metrics metrics = new Metrics("Tuinity", serverUUID, logFailedRequests, Bukkit.getLogger()); // Tuinity - we have our own bstats page
 
                 metrics.addCustomChart(new Metrics.SimplePie("minecraft_version", () -> {
                     String minecraftVersion = Bukkit.getVersion();
@@ -611,7 +611,7 @@ public class Metrics {
                 } else {
                     paperVersion = "unknown";
                 }
-                metrics.addCustomChart(new Metrics.SimplePie("paper_version", () -> paperVersion));
+                metrics.addCustomChart(new Metrics.SimplePie("tuinity_version", () -> paperVersion)); // Tuinity - we have our own bstats page
 
                 metrics.addCustomChart(new Metrics.DrilldownPie("java_version", () -> {
                     Map<String, Map<String, Integer>> map = new HashMap<>();
diff --git a/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java b/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java
index 4f3670b2bdb8b1b252e9f074a6af56a018a8c465..5c1ea572a97b130c3ff77624189b4acf3e9e9ece 100644
--- a/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java
+++ b/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java
@@ -179,11 +179,7 @@ public final class ChunkPacketBlockControllerAntiXray extends ChunkPacketBlockCo
             return;
         }
 
-        if (!Bukkit.isPrimaryThread()) {
-            // Plugins?
-            MinecraftServer.getServer().scheduleOnMain(() -> modifyBlocks(chunkPacket, chunkPacketInfo));
-            return;
-        }
+        // Folia - region threading
 
         LevelChunk chunk = chunkPacketInfo.getChunk();
         int x = chunk.getPos().x;
diff --git a/src/main/java/io/papermc/paper/adventure/ChatProcessor.java b/src/main/java/io/papermc/paper/adventure/ChatProcessor.java
index 309fe1162db195c7c3c94d785d6aa2700e42b08a..27f8c9b1c56cbf9af400a9ae15c2076a2db8b284 100644
--- a/src/main/java/io/papermc/paper/adventure/ChatProcessor.java
+++ b/src/main/java/io/papermc/paper/adventure/ChatProcessor.java
@@ -97,7 +97,7 @@ 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>() {
@@ -177,7 +177,7 @@ 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/chunk/system/ChunkSystem.java b/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java
index 6df1948b1204a7288ecb7238b6fc2a733f7d25b3..6a413abc67aa4dcbab64231be3eb13446d5cc820 100644
--- a/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java
+++ b/src/main/java/io/papermc/paper/chunk/system/ChunkSystem.java
@@ -91,6 +91,9 @@ public final class ChunkSystem {
         for (int index = 0, len = chunkMap.regionManagers.size(); index < len; ++index) {
             chunkMap.regionManagers.get(index).addChunk(holder.pos.x, holder.pos.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) {
@@ -98,6 +101,9 @@ public final class ChunkSystem {
         for (int index = 0, len = chunkMap.regionManagers.size(); index < len; ++index) {
             chunkMap.regionManagers.get(index).removeChunk(holder.pos.x, holder.pos.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) {
@@ -109,19 +115,19 @@ public final class ChunkSystem {
     }
 
     public static void onChunkTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().tickingChunks.add(chunk);
+        // Folia - region threading
     }
 
     public static void onChunkNotTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().tickingChunks.remove(chunk);
+        // Folia - region threading
     }
 
     public static void onChunkEntityTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().entityTickingChunks.add(chunk);
+        chunk.level.getCurrentWorldData().addEntityTickingChunks(chunk); // Folia - region threading
     }
 
     public static void onChunkNotEntityTicking(final LevelChunk chunk, final ChunkHolder holder) {
-        chunk.level.getChunkSource().entityTickingChunks.remove(chunk);
+        chunk.level.getCurrentWorldData().removeEntityTickingChunk(chunk); // Folia - region threading
     }
 
     public static ChunkHolder getUnloadingChunkHolder(final ServerLevel level, final int chunkX, final int chunkZ) {
diff --git a/src/main/java/io/papermc/paper/chunk/system/RegionisedPlayerChunkLoader.java b/src/main/java/io/papermc/paper/chunk/system/RegionisedPlayerChunkLoader.java
index cb170d1039fd9dadfbc27da0b181c00742e72025..5cccfcf45b3c3cdfdebdf47dc674934441cc0c4c 100644
--- a/src/main/java/io/papermc/paper/chunk/system/RegionisedPlayerChunkLoader.java
+++ b/src/main/java/io/papermc/paper/chunk/system/RegionisedPlayerChunkLoader.java
@@ -231,14 +231,14 @@ public class RegionisedPlayerChunkLoader {
 
     public void tick() {
         TickThread.ensureTickThread("Cannot tick player chunk loader async");
-        for (final ServerPlayer player : this.world.players()) {
+        for (final ServerPlayer player : this.world.getLocalPlayers()) { // Folia - region threding
             player.chunkLoader.update();
         }
     }
 
     public void tickMidTick() {
         final long time = System.nanoTime();
-        for (final ServerPlayer player : this.world.players()) {
+        for (final ServerPlayer player : this.world.getLocalPlayers()) { // Folia - region threading
             player.chunkLoader.midTickUpdate(time);
         }
     }
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 61c170555c8854b102c640b0b6a615f9f732edbf..687fc3e7ada3da9c5b938b0ffb9e8bcf90c2d1c7 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
@@ -187,7 +187,12 @@ 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
     }
 
     @Override
@@ -261,7 +266,9 @@ 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);
                         }
 
@@ -275,7 +282,9 @@ 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);
                         }
                     }
@@ -385,6 +394,8 @@ 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;
@@ -407,6 +418,7 @@ public final class EntityLookup implements LevelEntityGetter<Entity> {
                 LOGGER.warn("Failed to remove entity " + entity + " from entity slices (" + sectionX + "," + sectionZ + ")");
             }
         }
+
         entity.sectionX = entity.sectionY = entity.sectionZ = Integer.MIN_VALUE;
 
         this.entityByLock.writeLock();
@@ -823,6 +835,9 @@ 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 c6d20bc2f0eab737338db6b88dacb63f0decb66c..309b45885edc1400ae5a97cac7e5e5a19d73be0c 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
@@ -3,7 +3,6 @@ package io.papermc.paper.chunk.system.scheduling;
 import ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue;
 import ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor;
 import ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable;
-import co.aikar.timings.Timing;
 import com.google.common.collect.ImmutableList;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonObject;
@@ -19,10 +18,12 @@ import it.unimi.dsi.fastutil.longs.Long2IntMap;
 import it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap;
 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.longs.LongArrayList;
 import it.unimi.dsi.fastutil.longs.LongIterator;
 import it.unimi.dsi.fastutil.objects.ObjectRBTreeSet;
 import it.unimi.dsi.fastutil.objects.ReferenceLinkedOpenHashSet;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet;
 import net.minecraft.nbt.CompoundTag;
 import io.papermc.paper.chunk.system.ChunkSystem;
 import net.minecraft.server.MinecraftServer;
@@ -34,8 +35,6 @@ import net.minecraft.server.level.TicketType;
 import net.minecraft.util.SortedArraySet;
 import net.minecraft.util.Unit;
 import net.minecraft.world.level.ChunkPos;
-import net.minecraft.world.level.chunk.ChunkAccess;
-import net.minecraft.world.level.chunk.ChunkStatus;
 import org.bukkit.plugin.Plugin;
 import org.slf4j.Logger;
 import java.io.IOException;
@@ -54,6 +53,13 @@ import java.util.concurrent.locks.LockSupport;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Predicate;
 
+// Folia start - region threading
+import io.papermc.paper.threadedregions.RegionisedServer;
+import io.papermc.paper.threadedregions.ThreadedRegioniser;
+import io.papermc.paper.threadedregions.TickRegionScheduler;
+import io.papermc.paper.threadedregions.TickRegions;
+// Folia end - region threading
+
 public final class ChunkHolderManager {
 
     private static final Logger LOGGER = LogUtils.getClassLogger();
@@ -63,40 +69,201 @@ public final class ChunkHolderManager {
     public static final int ENTITY_TICKING_TICKET_LEVEL = 31;
     public static final int MAX_TICKET_LEVEL = ChunkMap.MAX_CHUNK_DISTANCE; // inclusive
 
-    private static final long NO_TIMEOUT_MARKER = -1L;
+    // Folia start - region threading
+    private static final long NO_TIMEOUT_MARKER = Long.MIN_VALUE;
+    private static final long PROBE_MARKER = Long.MIN_VALUE + 1;
+    // Folia end - region threading
 
-    final ReentrantLock ticketLock = new ReentrantLock();
+    public final ReentrantLock ticketLock = new ReentrantLock(); // Folia - region threading
 
     private final SWMRLong2ObjectHashTable<NewChunkHolder> chunkHolders = new SWMRLong2ObjectHashTable<>(16384, 0.25f);
-    private final Long2ObjectOpenHashMap<SortedArraySet<Ticket<?>>> tickets = new Long2ObjectOpenHashMap<>(8192, 0.25f);
-    // what a disaster of a name
-    // this is a map of removal tick to a map of chunks and the number of tickets a chunk has that are to expire that tick
-    private final Long2ObjectOpenHashMap<Long2IntOpenHashMap> removeTickToChunkExpireTicketCount = new Long2ObjectOpenHashMap<>();
+    // Folia - region threading
     private final ServerLevel world;
     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);
+        });
+        private long currentTick;
+        private final Long2ObjectOpenHashMap<SortedArraySet<Ticket<?>>> tickets = new Long2ObjectOpenHashMap<>(8192, 0.25f);
+        // what a disaster of a name
+        // this is a map of removal tick to a map of chunks and the number of tickets a chunk has that are to expire that tick
+        private final Long2ObjectOpenHashMap<Long2IntOpenHashMap> removeTickToChunkExpireTicketCount = new Long2ObjectOpenHashMap<>();
+
+        // special region threading fields
+        // this field contains chunk holders that were created in addTicketAtLevel
+        // because the chunk holders were created without a reliable unload hook (i.e creation for entity/poi loading,
+        // which always check for unload after their tasks finish) we need to do that ourselves later
+        private final ReferenceOpenHashSet<NewChunkHolder> specialCaseUnload = new ReferenceOpenHashSet<>();
+
+        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 long chunkManagerTickOffset = into.currentTick - this.currentTick;
+            for (final Iterator<Long2ObjectMap.Entry<SortedArraySet<Ticket<?>>>> iterator = this.tickets.long2ObjectEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Long2ObjectMap.Entry<SortedArraySet<Ticket<?>>> entry = iterator.next();
+                final SortedArraySet<Ticket<?>> oldTickets = entry.getValue();
+                final SortedArraySet<Ticket<?>> newTickets = SortedArraySet.create(Math.max(4, oldTickets.size() + 1));
+                for (final Ticket<?> ticket : oldTickets) {
+                    newTickets.add(
+                        new Ticket(ticket.getType(), ticket.getTicketLevel(), ticket.key,
+                            ticket.removalTick == NO_TIMEOUT_MARKER ? NO_TIMEOUT_MARKER : ticket.removalTick + chunkManagerTickOffset)
+                    );
+                }
+                into.tickets.put(entry.getLongKey(), newTickets);
+            }
+            for (final Iterator<Long2ObjectMap.Entry<Long2IntOpenHashMap>> iterator = this.removeTickToChunkExpireTicketCount.long2ObjectEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Long2ObjectMap.Entry<Long2IntOpenHashMap> entry = iterator.next();
+                into.removeTickToChunkExpireTicketCount.merge(
+                    (long)(entry.getLongKey() + chunkManagerTickOffset), entry.getValue(),
+                    (final Long2IntOpenHashMap t, final Long2IntOpenHashMap f) -> {
+                        for (final Iterator<Long2IntMap.Entry> itr = f.long2IntEntrySet().fastIterator(); itr.hasNext();) {
+                            final Long2IntMap.Entry e = itr.next();
+                            t.addTo(e.getLongKey(), e.getIntValue());
+                        }
+                        return t;
+                    }
+                );
+            }
+
+            // add them all
+            into.specialCaseUnload.addAll(this.specialCaseUnload);
         }
 
-        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
+            }
 
-        if (saveTickCompare != 0) {
-            return saveTickCompare;
+            for (final NewChunkHolder autoSave : this.autoSaveQueue) {
+                final int regionCoordinateX = autoSave.chunkX >> chunkToRegionShift;
+                final int regionCoordinateZ = autoSave.chunkZ >> chunkToRegionShift;
+
+                final HolderManagerRegionData data = regionToData.get(CoordinateUtils.getChunkKey(regionCoordinateX, regionCoordinateZ));
+                if (data != null) {
+                    data.autoSaveQueue.add(autoSave);
+                } // else: autoSave is an unloaded chunk holder
+            }
+            for (final HolderManagerRegionData data : dataSet) {
+                data.currentTick = this.currentTick;
+            }
+            for (final Iterator<Long2ObjectMap.Entry<SortedArraySet<Ticket<?>>>> iterator = this.tickets.long2ObjectEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Long2ObjectMap.Entry<SortedArraySet<Ticket<?>>> entry = iterator.next();
+                final long chunkKey = entry.getLongKey();
+                final int regionCoordinateX = CoordinateUtils.getChunkX(chunkKey) >> chunkToRegionShift;
+                final int regionCoordinateZ = CoordinateUtils.getChunkZ(chunkKey) >> chunkToRegionShift;
+
+                // can never be null, since a chunk holder exists if the ticket set is not empty
+                regionToData.get(CoordinateUtils.getChunkKey(regionCoordinateX, regionCoordinateZ)).tickets.put(chunkKey, entry.getValue());
+            }
+            for (final Iterator<Long2ObjectMap.Entry<Long2IntOpenHashMap>> iterator = this.removeTickToChunkExpireTicketCount.long2ObjectEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Long2ObjectMap.Entry<Long2IntOpenHashMap> entry = iterator.next();
+                final long tick = entry.getLongKey();
+                final Long2IntOpenHashMap chunkToCount = entry.getValue();
+
+                for (final Iterator<Long2IntMap.Entry> itr = chunkToCount.long2IntEntrySet().fastIterator(); itr.hasNext();) {
+                    final Long2IntMap.Entry e = itr.next();
+                    final long chunkKey = e.getLongKey();
+                    final int regionCoordinateX = CoordinateUtils.getChunkX(chunkKey) >> chunkToRegionShift;
+                    final int regionCoordinateZ = CoordinateUtils.getChunkZ(chunkKey) >> chunkToRegionShift;
+                    final int count = e.getIntValue();
+
+                    // can never be null, since a chunk holder exists if the ticket set is not empty
+                    final HolderManagerRegionData data = regionToData.get(CoordinateUtils.getChunkKey(regionCoordinateX, regionCoordinateZ));
+
+                    data.removeTickToChunkExpireTicketCount.computeIfAbsent(tick, (final long keyInMap) -> {
+                        return new Long2IntOpenHashMap();
+                    }).put(chunkKey, count);
+                }
+            }
+
+            for (final NewChunkHolder special : this.specialCaseUnload) {
+                final int regionCoordinateX = CoordinateUtils.getChunkX(special.chunkX) >> chunkToRegionShift;
+                final int regionCoordinateZ = CoordinateUtils.getChunkZ(special.chunkZ) >> chunkToRegionShift;
+
+                // can never be null, since this chunk holder is loaded
+                regionToData.get(CoordinateUtils.getChunkKey(regionCoordinateX, regionCoordinateZ)).specialCaseUnload.add(special);
+            }
         }
+    }
 
-        final long coord1 = CoordinateUtils.getChunkKey(c1.chunkX, c1.chunkZ);
-        final long coord2 = CoordinateUtils.getChunkKey(c2.chunkX, c2.chunkZ);
+    private ChunkHolderManager.HolderManagerRegionData getCurrentRegionData() {
+        final ThreadedRegioniser.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();
+    }
+
+    // MUST hold ticket lock
+    private ChunkHolderManager.HolderManagerRegionData getDataFor(final long key) {
+        return this.getDataFor(CoordinateUtils.getChunkX(key), CoordinateUtils.getChunkZ(key));
+    }
+
+    // MUST hold ticket lock
+    private ChunkHolderManager.HolderManagerRegionData getDataFor(final int chunkX, final int chunkZ) {
+        if (!this.ticketLock.isHeldByCurrentThread()) {
+            throw new IllegalStateException("Must hold ticket level lock");
+        }
+
+        final ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region
+            = this.world.regioniser.getRegionAtUnsynchronised(chunkX, chunkZ);
+
+        if (region == null) {
+            return null;
+        }
+
+        return region.getData().getHolderManagerRegionData();
+    }
+    // Folia end - region threading
+
 
     public ChunkHolderManager(final ServerLevel world, final ChunkTaskScheduler taskScheduler) {
         this.world = world;
@@ -129,8 +296,13 @@ 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() + "'");
@@ -140,9 +312,10 @@ 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();
         }
@@ -163,27 +336,34 @@ 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 = RegionisedServer.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 = RegionisedServer.getCurrentTick();
         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);
 
             holder.lastAutoSave = currentTick;
             if (holder.save(false, false) != null) {
@@ -197,15 +377,20 @@ public final class ChunkHolderManager {
 
         for (final NewChunkHolder holder : reschedule) {
             if (holder.getChunkStatus().isOrAfter(ChunkHolder.FullChunkStatus.BORDER)) {
-                this.autoSaveQueue.add(holder);
+                regionData.autoSaveQueue.add(holder);
             }
         }
     }
 
     public void saveAllChunks(final boolean flush, final boolean shutdown, final boolean logProgress) {
+        // 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) {
+        // Folia end - region threading
         final List<NewChunkHolder> holders = this.getChunkHolders();
 
-        if (logProgress) {
+        if (first && logProgress) { // Folia - region threading
             LOGGER.info("Saving all chunkholders for world '" + this.world.getWorld().getName() + "'");
         }
 
@@ -213,7 +398,7 @@ 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;
@@ -224,6 +409,12 @@ 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) {
@@ -256,7 +447,7 @@ public final class ChunkHolderManager {
                 }
             }
         }
-        if (flush) {
+        if (last && flush) { // Folia - region threading
             RegionFileIOThread.flush();
         }
         if (logProgress) {
@@ -290,18 +481,16 @@ public final class ChunkHolderManager {
     }
 
     public boolean hasTickets() {
-        this.ticketLock.lock();
-        try {
-            return !this.tickets.isEmpty();
-        } finally {
-            this.ticketLock.unlock();
-        }
+        return !this.getTicketsCopy().isEmpty(); // Folia - region threading
     }
 
     public String getTicketDebugString(final long coordinate) {
         this.ticketLock.lock();
         try {
-            final SortedArraySet<Ticket<?>> tickets = this.tickets.get(coordinate);
+            // Folia start - region threading
+            final ChunkHolderManager.HolderManagerRegionData holderManagerRegionData = this.getDataFor(coordinate);
+            final SortedArraySet<Ticket<?>> tickets = holderManagerRegionData == null ? null : holderManagerRegionData.tickets.get(coordinate);
+            // Folia end - region threading
 
             return tickets != null ? tickets.first().toString() : "no_ticket";
         } finally {
@@ -312,7 +501,17 @@ public final class ChunkHolderManager {
     public Long2ObjectOpenHashMap<SortedArraySet<Ticket<?>>> getTicketsCopy() {
         this.ticketLock.lock();
         try {
-            return this.tickets.clone();
+            // Folia start - region threading
+            Long2ObjectOpenHashMap<SortedArraySet<Ticket<?>>> ret = new Long2ObjectOpenHashMap<>();
+            this.world.regioniser.computeForAllRegions((region) -> {
+                for (final LongIterator iterator = region.getData().getHolderManagerRegionData().tickets.keySet().longIterator(); iterator.hasNext();) {
+                    final long chunk = iterator.nextLong();
+
+                    ret.put(chunk, region.getData().getHolderManagerRegionData().tickets.get(chunk));
+                }
+            });
+            return ret;
+            // Folia end - region threading
         } finally {
             this.ticketLock.unlock();
         }
@@ -322,7 +521,11 @@ public final class ChunkHolderManager {
         ImmutableList.Builder<Plugin> ret;
         this.ticketLock.lock();
         try {
-            SortedArraySet<Ticket<?>> tickets = this.tickets.get(ChunkPos.asLong(x, z));
+            // Folia start - region threading
+            final long coordinate = CoordinateUtils.getChunkKey(x, z);
+            final ChunkHolderManager.HolderManagerRegionData holderManagerRegionData = this.getDataFor(coordinate);
+            final SortedArraySet<Ticket<?>> tickets = holderManagerRegionData == null ? null : holderManagerRegionData.tickets.get(coordinate);
+            // Folia end - region threading
 
             if (tickets == null) {
                 return Collections.emptyList();
@@ -377,10 +580,27 @@ public final class ChunkHolderManager {
 
         this.ticketLock.lock();
         try {
-            final long removeTick = removeDelay == 0 ? NO_TIMEOUT_MARKER : this.currentTick + removeDelay;
+            // Folia start - region threading
+            NewChunkHolder holder = this.chunkHolders.get(chunk);
+            final boolean addToSpecial = holder == null;
+            if (addToSpecial) {
+                // we need to guarantee that a chunk holder exists for each ticket
+                // this must be executed before retrieving the holder manager data for a target chunk, to ensure the
+                // region will exist
+                this.chunkHolders.put(chunk, holder = this.createChunkHolder(chunk));
+            }
+
+            final ChunkHolderManager.HolderManagerRegionData targetData = this.getDataFor(chunk);
+            if (addToSpecial) {
+                // no guarantee checkUnload is called for this chunk holder - by adding to the special case unload,
+                // the unload chunks call will perform it
+                targetData.specialCaseUnload.add(holder);
+            }
+            // Folia end - region threading
+            final long removeTick = removeDelay == 0 ? NO_TIMEOUT_MARKER : targetData.currentTick + removeDelay; // Folia - region threading
             final Ticket<T> ticket = new Ticket<>(type, level, identifier, removeTick);
 
-            final SortedArraySet<Ticket<?>> ticketsAtChunk = this.tickets.computeIfAbsent(chunk, (final long keyInMap) -> {
+            final SortedArraySet<Ticket<?>> ticketsAtChunk = targetData.tickets.computeIfAbsent(chunk, (final long keyInMap) -> { // Folia - region threading
                 return SortedArraySet.create(4);
             });
 
@@ -392,25 +612,25 @@ public final class ChunkHolderManager {
                 final long oldRemovalTick = current.removalTick;
                 if (removeTick != oldRemovalTick) {
                     if (oldRemovalTick != NO_TIMEOUT_MARKER) {
-                        final Long2IntOpenHashMap removeCounts = this.removeTickToChunkExpireTicketCount.get(oldRemovalTick);
+                        final Long2IntOpenHashMap removeCounts = targetData.removeTickToChunkExpireTicketCount.get(oldRemovalTick); // Folia - region threading
                         final int prevCount = removeCounts.addTo(chunk, -1);
 
                         if (prevCount == 1) {
                             removeCounts.remove(chunk);
                             if (removeCounts.isEmpty()) {
-                                this.removeTickToChunkExpireTicketCount.remove(oldRemovalTick);
+                                targetData.removeTickToChunkExpireTicketCount.remove(oldRemovalTick); // Folia - region threading
                             }
                         }
                     }
                     if (removeTick != NO_TIMEOUT_MARKER) {
-                        this.removeTickToChunkExpireTicketCount.computeIfAbsent(removeTick, (final long keyInMap) -> {
+                        targetData.removeTickToChunkExpireTicketCount.computeIfAbsent(removeTick, (final long keyInMap) -> { // Folia - region threading
                             return new Long2IntOpenHashMap();
                         }).addTo(chunk, 1);
                     }
                 }
             } else {
                 if (removeTick != NO_TIMEOUT_MARKER) {
-                    this.removeTickToChunkExpireTicketCount.computeIfAbsent(removeTick, (final long keyInMap) -> {
+                    targetData.removeTickToChunkExpireTicketCount.computeIfAbsent(removeTick, (final long keyInMap) -> { // Folia - region threading
                         return new Long2IntOpenHashMap();
                     }).addTo(chunk, 1);
                 }
@@ -439,35 +659,43 @@ public final class ChunkHolderManager {
             return false;
         }
 
+        final ChunkHolderManager.HolderManagerRegionData currRegionData = this.getCurrentRegionData(); // Folia - region threading
+
         this.ticketLock.lock();
         try {
-            final SortedArraySet<Ticket<?>> ticketsAtChunk = this.tickets.get(chunk);
+            // Folia start - region threading
+            final ChunkHolderManager.HolderManagerRegionData targetData = this.getDataFor(chunk);
+
+            final boolean sameRegion = currRegionData == targetData;
+
+            final SortedArraySet<Ticket<?>> ticketsAtChunk = targetData == null ? null : targetData.tickets.get(chunk);
+            // Folia end - region threading
             if (ticketsAtChunk == null) {
                 return false;
             }
 
             final int oldLevel = getTicketLevelAt(ticketsAtChunk);
-            final Ticket<T> ticket = (Ticket<T>)ticketsAtChunk.removeAndGet(new Ticket<>(type, level, identifier, -2L));
+            final Ticket<T> ticket = (Ticket<T>)ticketsAtChunk.removeAndGet(new Ticket<>(type, level, identifier, PROBE_MARKER)); // Folia - region threading
 
             if (ticket == null) {
                 return false;
             }
 
             if (ticketsAtChunk.isEmpty()) {
-                this.tickets.remove(chunk);
+                targetData.tickets.remove(chunk); // Folia - region threading
             }
 
             final int newLevel = getTicketLevelAt(ticketsAtChunk);
 
             final long removeTick = ticket.removalTick;
             if (removeTick != NO_TIMEOUT_MARKER) {
-                final Long2IntOpenHashMap removeCounts = this.removeTickToChunkExpireTicketCount.get(removeTick);
+                final Long2IntOpenHashMap removeCounts = targetData.removeTickToChunkExpireTicketCount.get(removeTick); // Folia - region threading
                 final int currCount = removeCounts.addTo(chunk, -1);
 
                 if (currCount == 1) {
                     removeCounts.remove(chunk);
                     if (removeCounts.isEmpty()) {
-                        this.removeTickToChunkExpireTicketCount.remove(removeTick);
+                        targetData.removeTickToChunkExpireTicketCount.remove(removeTick); // Folia - region threading
                     }
                 }
             }
@@ -476,6 +704,13 @@ public final class ChunkHolderManager {
                 this.updateTicketLevel(chunk, newLevel);
             }
 
+            // Folia start - region threading
+            // if we're not the target region, we should not change the ticket levels while the target region may be ticking
+            if (!sameRegion && newLevel > level) {
+                this.addTicketAtLevel(TicketType.UNKNOWN, chunk, level, new ChunkPos(chunk));
+            }
+            // Folia end - region threading
+
             return true;
         } finally {
             this.ticketLock.unlock();
@@ -516,24 +751,33 @@ public final class ChunkHolderManager {
 
         this.ticketLock.lock();
         try {
-            for (final LongIterator iterator = new LongArrayList(this.tickets.keySet()).longIterator(); iterator.hasNext();) {
-                final long chunk = iterator.nextLong();
+            // Folia start - region threading
+            this.world.regioniser.computeForAllRegions((region) -> {
+                for (final LongIterator iterator = new LongArrayList(region.getData().getHolderManagerRegionData().tickets.keySet()).longIterator(); iterator.hasNext();) {
+                    final long chunk = iterator.nextLong();
 
-                this.removeTicketAtLevel(ticketType, chunk, ticketLevel, ticketIdentifier);
-            }
+                    this.removeTicketAtLevel(ticketType, chunk, ticketLevel, ticketIdentifier);
+                }
+            });
+            // Folia end - region threading
         } finally {
             this.ticketLock.unlock();
         }
     }
 
     public void tick() {
-        TickThread.ensureTickThread("Cannot tick ticket manager off-main");
+        // Folia start - region threading
+        final ChunkHolderManager.HolderManagerRegionData data = this.getCurrentRegionData();
+        if (data == null) {
+            throw new IllegalStateException("Not running tick() while on a region");
+        }
+        // Folia end - region threading
 
         this.ticketLock.lock();
         try {
-            final long tick = ++this.currentTick;
+            final long tick = ++data.currentTick; // Folia - region threading
 
-            final Long2IntOpenHashMap toRemove = this.removeTickToChunkExpireTicketCount.remove(tick);
+            final Long2IntOpenHashMap toRemove = data.removeTickToChunkExpireTicketCount.remove(tick); // Folia - region threading
 
             if (toRemove == null) {
                 return;
@@ -546,10 +790,10 @@ public final class ChunkHolderManager {
             for (final LongIterator iterator = toRemove.keySet().longIterator(); iterator.hasNext();) {
                 final long chunk = iterator.nextLong();
 
-                final SortedArraySet<Ticket<?>> tickets = this.tickets.get(chunk);
+                final SortedArraySet<Ticket<?>> tickets = data.tickets.get(chunk); // Folia - region threading
                 tickets.removeIf(expireNow);
                 if (tickets.isEmpty()) {
-                    this.tickets.remove(chunk);
+                    data.tickets.remove(chunk); // Folia - region threading
                     this.ticketLevelPropagator.removeSource(chunk);
                 } else {
                     this.ticketLevelPropagator.setSource(chunk, convertBetweenTicketLevels(tickets.first().getTicketLevel()));
@@ -798,30 +1042,62 @@ 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));
+        final Long2ObjectOpenHashMap<List<NewChunkHolder>> sectionToUpdates = new Long2ObjectOpenHashMap<>();
+        final List<NewChunkHolder> thisRegionHolders = new ArrayList<>();
+
+        final int regionShift = this.world.regioniser.sectionChunkShift;
+        final ThreadedRegioniser.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);
+            }
+        }
+
+        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);
             }
         }
     }
 
     final ReferenceLinkedOpenHashSet<NewChunkHolder> unloadQueue = new ReferenceLinkedOpenHashSet<>();
 
+    /*
+     * Note: Only called on chunk holders that the current ticking region owns
+     */
     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
         this.chunkHolders.remove(CoordinateUtils.getChunkKey(holder.chunkX, holder.chunkZ));
     }
 
@@ -839,23 +1115,42 @@ public final class ChunkHolderManager {
             throw new IllegalStateException("Cannot hold scheduling lock while calling processUnloads");
         }
 
+        final ChunkHolderManager.HolderManagerRegionData currentData = this.getCurrentRegionData(); // Folia - region threading
+
         final List<NewChunkHolder.UnloadState> unloadQueue;
         final List<ChunkProgressionTask> scheduleList = new ArrayList<>();
         this.ticketLock.lock();
         try {
             this.taskScheduler.schedulingLock.lock();
             try {
+                // Folia start - region threading
+                for (final NewChunkHolder special : currentData.specialCaseUnload) {
+                    special.checkUnload();
+                }
+                currentData.specialCaseUnload.clear();
+                // Folia end - region threading
                 if (this.unloadQueue.isEmpty()) {
                     return;
                 }
                 // in order to ensure all chunks in the unload queue do not have a pending ticket level update,
                 // process them now
                 this.processTicketUpdates(false, false, scheduleList);
-                unloadQueue = new ArrayList<>((int)(this.unloadQueue.size() * 0.05) + 1);
 
-                final int unloadCount = Math.max(50, (int)(this.unloadQueue.size() * 0.05));
-                for (int i = 0; i < unloadCount && !this.unloadQueue.isEmpty(); ++i) {
-                    final NewChunkHolder chunkHolder = this.unloadQueue.removeFirst();
+                // Folia start - region threading
+                final ArrayDeque<NewChunkHolder> toUnload = new ArrayDeque<>();
+                // The unload queue is globally maintained, but we can only unload chunks in our region
+                for (final NewChunkHolder holder : this.unloadQueue) {
+                    if (TickThread.isTickThreadFor(this.world, holder.chunkX, holder.chunkZ)) {
+                        toUnload.add(holder);
+                    }
+                }
+                // Folia end - region threading
+
+                final int unloadCount = Math.max(50, (int)(toUnload.size() * 0.05)); // Folia - region threading
+                unloadQueue = new ArrayList<>(unloadCount + 1); // Folia - region threading
+                for (int i = 0; i < unloadCount && !toUnload.isEmpty(); ++i) { // Folia - region threading
+                    final NewChunkHolder chunkHolder = toUnload.removeFirst(); // Folia - region threading
+                    this.unloadQueue.remove(chunkHolder); // Folia - region threading
                     if (chunkHolder.isSafeToUnload() != null) {
                         LOGGER.error("Chunkholder " + chunkHolder + " is not safe to unload but is inside the unload queue?");
                         continue;
@@ -1193,7 +1488,12 @@ public final class ChunkHolderManager {
 
     // only call on tick thread
     protected final boolean processPendingFullUpdate() {
-        final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = this.pendingFullLoadUpdate;
+        final HolderManagerRegionData data = this.getCurrentRegionData();
+        if (data == null) {
+            return false;
+        }
+
+        final ArrayDeque<NewChunkHolder> pendingFullLoadUpdate = data.pendingFullLoadUpdate;
 
         boolean ret = false;
 
@@ -1204,9 +1504,7 @@ 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);
                 changedFullStatus.clear();
             }
         }
@@ -1256,7 +1554,7 @@ 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);
@@ -1275,60 +1573,73 @@ public final class ChunkHolderManager {
             holders.add(holder.getDebugJson());
         }
 
-        final JsonArray removeTickToChunkExpireTicketCount = new JsonArray();
-        ret.add("remove_tick_to_chunk_expire_ticket_count", removeTickToChunkExpireTicketCount);
+        // Folia start - region threading
+        final JsonArray regions = new JsonArray();
+        ret.add("regions", regions);
+        this.world.regioniser.computeForAllRegionsUnsynchronised((region) -> {
+            final JsonObject regionJson = new JsonObject();
+            regions.add(regionJson);
+
+            final TickRegions.TickRegionData regionData = region.getData();
 
-        for (final Long2ObjectMap.Entry<Long2IntOpenHashMap> tickEntry : this.removeTickToChunkExpireTicketCount.long2ObjectEntrySet()) {
-            final long tick = tickEntry.getLongKey();
-            final Long2IntOpenHashMap coordinateToCount = tickEntry.getValue();
+            regionJson.addProperty("current_tick", Long.valueOf(regionData.getCurrentTick()));
 
-            final JsonObject tickJson = new JsonObject();
-            removeTickToChunkExpireTicketCount.add(tickJson);
+            final JsonArray removeTickToChunkExpireTicketCount = new JsonArray();
+            regionJson.add("remove_tick_to_chunk_expire_ticket_count", removeTickToChunkExpireTicketCount);
 
-            tickJson.addProperty("tick", Long.valueOf(tick));
+            for (final Long2ObjectMap.Entry<Long2IntOpenHashMap> tickEntry : regionData.getHolderManagerRegionData().removeTickToChunkExpireTicketCount.long2ObjectEntrySet()) {
+                final long tick = tickEntry.getLongKey();
+                final Long2IntOpenHashMap coordinateToCount = tickEntry.getValue();
 
-            final JsonArray tickEntries = new JsonArray();
-            tickJson.add("entries", tickEntries);
+                final JsonObject tickJson = new JsonObject();
+                removeTickToChunkExpireTicketCount.add(tickJson);
 
-            for (final Long2IntMap.Entry entry : coordinateToCount.long2IntEntrySet()) {
-                final long coordinate = entry.getLongKey();
-                final int count = entry.getIntValue();
+                tickJson.addProperty("tick", Long.valueOf(tick));
 
-                final JsonObject entryJson = new JsonObject();
-                tickEntries.add(entryJson);
+                final JsonArray tickEntries = new JsonArray();
+                tickJson.add("entries", tickEntries);
 
-                entryJson.addProperty("chunkX", Long.valueOf(CoordinateUtils.getChunkX(coordinate)));
-                entryJson.addProperty("chunkZ", Long.valueOf(CoordinateUtils.getChunkZ(coordinate)));
-                entryJson.addProperty("count", Integer.valueOf(count));
+                for (final Long2IntMap.Entry entry : coordinateToCount.long2IntEntrySet()) {
+                    final long coordinate = entry.getLongKey();
+                    final int count = entry.getIntValue();
+
+                    final JsonObject entryJson = new JsonObject();
+                    tickEntries.add(entryJson);
+
+                    entryJson.addProperty("chunkX", Long.valueOf(CoordinateUtils.getChunkX(coordinate)));
+                    entryJson.addProperty("chunkZ", Long.valueOf(CoordinateUtils.getChunkZ(coordinate)));
+                    entryJson.addProperty("count", Integer.valueOf(count));
+                }
             }
-        }
 
-        final JsonArray allTicketsJson = new JsonArray();
-        ret.add("tickets", allTicketsJson);
+            final JsonArray allTicketsJson = new JsonArray();
+            regionJson.add("tickets", allTicketsJson);
 
-        for (final Long2ObjectMap.Entry<SortedArraySet<Ticket<?>>> coordinateTickets : this.tickets.long2ObjectEntrySet()) {
-            final long coordinate = coordinateTickets.getLongKey();
-            final SortedArraySet<Ticket<?>> tickets = coordinateTickets.getValue();
+            for (final Long2ObjectMap.Entry<SortedArraySet<Ticket<?>>> coordinateTickets : regionData.getHolderManagerRegionData().tickets.long2ObjectEntrySet()) {
+                final long coordinate = coordinateTickets.getLongKey();
+                final SortedArraySet<Ticket<?>> tickets = coordinateTickets.getValue();
 
-            final JsonObject coordinateJson = new JsonObject();
-            allTicketsJson.add(coordinateJson);
+                final JsonObject coordinateJson = new JsonObject();
+                allTicketsJson.add(coordinateJson);
 
-            coordinateJson.addProperty("chunkX", Long.valueOf(CoordinateUtils.getChunkX(coordinate)));
-            coordinateJson.addProperty("chunkZ", Long.valueOf(CoordinateUtils.getChunkZ(coordinate)));
+                coordinateJson.addProperty("chunkX", Long.valueOf(CoordinateUtils.getChunkX(coordinate)));
+                coordinateJson.addProperty("chunkZ", Long.valueOf(CoordinateUtils.getChunkZ(coordinate)));
 
-            final JsonArray ticketsSerialized = new JsonArray();
-            coordinateJson.add("tickets", ticketsSerialized);
+                final JsonArray ticketsSerialized = new JsonArray();
+                coordinateJson.add("tickets", ticketsSerialized);
 
-            for (final Ticket<?> ticket : tickets) {
-                final JsonObject ticketSerialized = new JsonObject();
-                ticketsSerialized.add(ticketSerialized);
+                for (final Ticket<?> ticket : tickets) {
+                    final JsonObject ticketSerialized = new JsonObject();
+                    ticketsSerialized.add(ticketSerialized);
 
-                ticketSerialized.addProperty("type", ticket.getType().toString());
-                ticketSerialized.addProperty("level", Integer.valueOf(ticket.getTicketLevel()));
-                ticketSerialized.addProperty("identifier", Objects.toString(ticket.key));
-                ticketSerialized.addProperty("remove_tick", Long.valueOf(ticket.removalTick));
+                    ticketSerialized.addProperty("type", ticket.getType().toString());
+                    ticketSerialized.addProperty("level", Integer.valueOf(ticket.getTicketLevel()));
+                    ticketSerialized.addProperty("identifier", Objects.toString(ticket.key));
+                    ticketSerialized.addProperty("remove_tick", Long.valueOf(ticket.removalTick));
+                }
             }
-        }
+        });
+        // Folia end - region threading
 
         return ret;
     }
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 84cc9397237fa0c17aa1012dfb5683c90eb6d3b8..93b666893a9755e426701f5c2849fc0fb2026bb7 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
@@ -113,7 +113,7 @@ public final class ChunkTaskScheduler {
     public final PrioritisedThreadPool.PrioritisedPoolExecutor parallelGenExecutor;
     public final PrioritisedThreadPool.PrioritisedPoolExecutor loadExecutor;
 
-    private final PrioritisedThreadedTaskQueue mainThreadExecutor = new PrioritisedThreadedTaskQueue();
+    // Folia - regionised ticking
 
     final ReentrantLock schedulingLock = new ReentrantLock();
     public final ChunkHolderManager chunkHolderManager;
@@ -240,14 +240,13 @@ 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) {
@@ -267,7 +266,7 @@ public final class ChunkTaskScheduler {
     public void scheduleTickingState(final int chunkX, final int chunkZ, final ChunkHolder.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);
@@ -380,9 +379,50 @@ public final class ChunkTaskScheduler {
         });
     }
 
+    // Folia start - region threading
+    // only appropriate to use with ServerLevel#syncLoadNonFull
+    public boolean beginChunkLoadForNonFullSync(final int chunkX, final int chunkZ, final ChunkStatus toStatus,
+                                                final PrioritisedExecutor.Priority priority) {
+        final long chunkKey = CoordinateUtils.getChunkKey(chunkX, chunkZ);
+        final int minLevel = 33 + ChunkStatus.getDistance(toStatus);
+        final List<ChunkProgressionTask> tasks = new ArrayList<>();
+        this.chunkHolderManager.ticketLock.lock();
+        try {
+            this.schedulingLock.lock();
+            try {
+                final NewChunkHolder chunkHolder = this.chunkHolderManager.getChunkHolder(chunkKey);
+                if (chunkHolder == null || chunkHolder.getTicketLevel() > minLevel) {
+                    return false;
+                } else {
+                    final ChunkStatus genStatus = chunkHolder.getCurrentGenStatus();
+                    if (genStatus != null && genStatus.isOrAfter(toStatus)) {
+                        return true;
+                    } else {
+                        chunkHolder.raisePriority(priority);
+
+                        if (!chunkHolder.upgradeGenTarget(toStatus)) {
+                            this.schedule(chunkX, chunkZ, toStatus, chunkHolder, tasks);
+                        }
+                    }
+                }
+            } finally {
+                this.schedulingLock.unlock();
+            }
+        } finally {
+            this.chunkHolderManager.ticketLock.unlock();
+        }
+
+        for (int i = 0, len = tasks.size(); i < len; ++i) {
+            tasks.get(i).schedule();
+        }
+
+        return true;
+    }
+    // Folia end - region threading
+
     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);
@@ -409,7 +449,7 @@ 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);
@@ -449,7 +489,9 @@ 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 {
@@ -463,7 +505,7 @@ public final class ChunkTaskScheduler {
             tasks.get(i).schedule();
         }
 
-        if (!scheduled) {
+        if (loadCallback != null && !scheduled) {
             // couldn't schedule
             try {
                 loadCallback.accept(chunk);
@@ -652,7 +694,7 @@ 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
     }
 
     /**
@@ -660,7 +702,7 @@ 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) {
@@ -669,28 +711,33 @@ 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().regionisedServer.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().regionisedServer.taskQueue.queueChunkTask(this.world, chunkX, chunkZ, run, priority); // Folia - regionised ticking
     }
 
-    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 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().regionisedServer.taskQueue.queueChunkTask(ChunkTaskScheduler.this.world, chunkX, chunkZ, run, priority);
+        });
+        return ret;
     }
+    // Folia end - region threading
+
+    // Folia - regionised ticking
 
     public boolean halt(final boolean sync, final long maxWaitNS) {
         this.lightExecutor.halt();
@@ -699,6 +746,7 @@ 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.lightExecutor.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 8013dd333e27aa5fd0beb431fa32491eec9f5246..3b70ccd8e0b1ada943f57faf99c23b2935249cf6 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
@@ -708,7 +708,7 @@ public final class NewChunkHolder {
     boolean killed;
 
     // must hold scheduling lock
-    private void checkUnload() {
+    void checkUnload() { // Folia - region threading
         if (this.killed) {
             return;
         }
@@ -1412,7 +1412,7 @@ 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);
@@ -1455,7 +1455,7 @@ 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);
@@ -1715,7 +1715,7 @@ 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) {}
 
@@ -1865,7 +1865,7 @@ 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);
             }
@@ -1913,7 +1913,7 @@ 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;
@@ -1939,7 +1939,7 @@ 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/PaperCommand.java b/src/main/java/io/papermc/paper/command/PaperCommand.java
index 92154550b41b2e1d03deb1271b71bb3baa735e0a..bc97ad0ae019edb52e189e44d0d698973c8792a0 100644
--- a/src/main/java/io/papermc/paper/command/PaperCommand.java
+++ b/src/main/java/io/papermc/paper/command/PaperCommand.java
@@ -50,7 +50,7 @@ public final class PaperCommand extends Command {
         commands.put(Set.of("debug", "chunkinfo", "holderinfo"), new ChunkDebugCommand());
         commands.put(Set.of("syncloadinfo"), new SyncLoadInfoCommand());
         commands.put(Set.of("dumpitem"), new DumpItemCommand());
-        commands.put(Set.of("mobcaps", "playermobcaps"), new MobcapsCommand());
+        commands.put(Set.of("mobcaps"), new MobcapsCommand()); // Folia - region threading - revert per player mob caps
         commands.put(Set.of("dumplisteners"), new DumpListenersCommand());
 
         return commands.entrySet().stream()
diff --git a/src/main/java/io/papermc/paper/command/PaperCommands.java b/src/main/java/io/papermc/paper/command/PaperCommands.java
index d31b5ed47cffc61c90c926a0cd2005b72ebddfc5..9b9c5bda073914a0588d4a6c8b584e5ce23468d8 100644
--- a/src/main/java/io/papermc/paper/command/PaperCommands.java
+++ b/src/main/java/io/papermc/paper/command/PaperCommands.java
@@ -17,7 +17,10 @@ public final class PaperCommands {
     private static final Map<String, Command> COMMANDS = new HashMap<>();
     static {
         COMMANDS.put("paper", new PaperCommand("paper"));
-        COMMANDS.put("mspt", new MSPTCommand("mspt"));
+        COMMANDS.put("tpa", new io.papermc.paper.threadedregions.commands.CommandsTPA()); // Folia - region threading
+        COMMANDS.put("tpaaccept", new io.papermc.paper.threadedregions.commands.CommandsTPAAccept()); // Folia - region threading
+        COMMANDS.put("tpadeny", new io.papermc.paper.threadedregions.commands.CommandsTPADeny()); // Folia - region threading
+        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/HeapDumpCommand.java b/src/main/java/io/papermc/paper/command/subcommands/HeapDumpCommand.java
index cd2e4d792e972b8bf1e07b8961594a670ae949cf..6c24e8567d303db35328fe4f0a7b05df16f3590a 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.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
         this.dumpHeap(sender);
+        }); // Folia - region threading
         return true;
     }
 
diff --git a/src/main/java/io/papermc/paper/command/subcommands/MobcapsCommand.java b/src/main/java/io/papermc/paper/command/subcommands/MobcapsCommand.java
index 99c41a39cdad0271d089c6e03bebfdafba1aaa57..41aaa709dc2e474f23e759ebc51f33021c4f5485 100644
--- a/src/main/java/io/papermc/paper/command/subcommands/MobcapsCommand.java
+++ b/src/main/java/io/papermc/paper/command/subcommands/MobcapsCommand.java
@@ -46,7 +46,7 @@ public final class MobcapsCommand implements PaperSubcommand {
     public boolean execute(final CommandSender sender, final String subCommand, final String[] args) {
         switch (subCommand) {
             case "mobcaps" -> this.printMobcaps(sender, args);
-            case "playermobcaps" -> this.printPlayerMobcaps(sender, args);
+            //case "playermobcaps" -> this.printPlayerMobcaps(sender, args); // Folia - region threading - revert per player mob caps
         }
         return true;
     }
@@ -55,7 +55,7 @@ public final class MobcapsCommand implements PaperSubcommand {
     public List<String> tabComplete(final CommandSender sender, final String subCommand, final String[] args) {
         return switch (subCommand) {
             case "mobcaps" -> CommandUtil.getListMatchingLast(sender, args, this.suggestMobcaps(args));
-            case "playermobcaps" -> CommandUtil.getListMatchingLast(sender, args, this.suggestPlayerMobcaps(sender, args));
+            //case "playermobcaps" -> CommandUtil.getListMatchingLast(sender, args, this.suggestPlayerMobcaps(sender, args)); // Folia - region threading - revert per player mob caps
             default -> throw new IllegalArgumentException();
         };
     }
@@ -140,41 +140,7 @@ public final class MobcapsCommand implements PaperSubcommand {
         }
     }
 
-    private void printPlayerMobcaps(final CommandSender sender, final String[] args) {
-        final @Nullable Player player;
-        if (args.length == 0) {
-            if (sender instanceof Player pl) {
-                player = pl;
-            } else {
-                sender.sendMessage(Component.text("Must specify a player! ex: '/paper playermobcount playerName'", NamedTextColor.RED));
-                return;
-            }
-        } else if (args.length == 1) {
-            final String input = args[0];
-            player = Bukkit.getPlayerExact(input);
-            if (player == null) {
-                sender.sendMessage(Component.text("Could not find player named '" + input + "'", NamedTextColor.RED));
-                return;
-            }
-        } else {
-            sender.sendMessage(Component.text("Too many arguments!", NamedTextColor.RED));
-            return;
-        }
-
-        final ServerPlayer serverPlayer = ((CraftPlayer) player).getHandle();
-        final ServerLevel level = serverPlayer.getLevel();
-
-        if (!level.paperConfig().entities.spawning.perPlayerMobSpawns) {
-            sender.sendMessage(Component.text("Use '/paper mobcaps' for worlds where per-player mob spawning is disabled.", NamedTextColor.RED));
-            return;
-        }
-
-        sender.sendMessage(Component.join(JoinConfiguration.noSeparators(), Component.text("Mobcaps for player: "), Component.text(player.getName(), NamedTextColor.GREEN)));
-        sender.sendMessage(createMobcapsComponent(
-            category -> level.chunkSource.chunkMap.getMobCountNear(serverPlayer, category),
-            category -> level.getWorld().getSpawnLimitUnsafe(org.bukkit.craftbukkit.util.CraftSpawnCategory.toBukkit(category))
-        ));
-    }
+    // Folia - region threading - revert per player mob caps
 
     private static Component createMobcapsComponent(final ToIntFunction<MobCategory> countGetter, final ToIntFunction<MobCategory> limitGetter) {
         return MOB_CATEGORY_COLORS.entrySet().stream()
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..0f641ac581243db55a667ad8bc5d1110206b389e 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.RegionisedServer.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 9f5f0d8ddc8f480b48079c70e38c9c08eff403f6..3b83f25a24d6f9cdbf131d5a4432fb4ad018be4e 100644
--- a/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
+++ b/src/main/java/io/papermc/paper/configuration/GlobalConfiguration.java
@@ -288,6 +288,18 @@ public class GlobalConfiguration extends ConfigurationPart {
         public boolean strictAdvancementDimensionCheck = false;
     }
 
+    // Folia start - threaded regions
+    public ThreadedRegions threadedRegions;
+    public class ThreadedRegions extends Post {
+
+        public int threads = -1;
+
+        @Override
+        public void postProcess() {
+            io.papermc.paper.threadedregions.TickRegions.init(this);
+        }
+    }
+    // Folia end - threaded regions
     public ChunkLoadingBasic chunkLoadingBasic;
 
     public class ChunkLoadingBasic extends ConfigurationPart {
diff --git a/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java b/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java
index 4532f3a0d74feae0a1249b53e1bfbc18a8808b32..f06681b3e66234b8805e6aa2d26fd535fbdb0aff 100644
--- a/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java
+++ b/src/main/java/io/papermc/paper/configuration/WorldConfiguration.java
@@ -128,7 +128,7 @@ public class WorldConfiguration extends ConfigurationPart {
             public boolean filterBadTileEntityNbtFromFallingBlocks = true;
             public List<NbtPathArgument.NbtPath> filteredEntityTagNbtPaths = NbtPathSerializer.fromString(List.of("Pos", "Motion", "SleepingX", "SleepingY", "SleepingZ"));
             public boolean disableMobSpawnerSpawnEggTransformation = false;
-            public boolean perPlayerMobSpawns = true;
+            //public boolean perPlayerMobSpawns = true; // Folia - region threading - revert per player mob caps
             public boolean scanForLegacyEnderDragon = true;
             @MergeMap
             public Reference2IntMap<MobCategory> spawnLimits = Util.make(new Reference2IntOpenHashMap<>(NaturalSpawner.SPAWNING_CATEGORIES.length), map -> Arrays.stream(NaturalSpawner.SPAWNING_CATEGORIES).forEach(mobCategory -> map.put(mobCategory, -1)));
diff --git a/src/main/java/io/papermc/paper/threadedregions/EntityScheduler.java b/src/main/java/io/papermc/paper/threadedregions/EntityScheduler.java
new file mode 100644
index 0000000000000000000000000000000000000000..d9687722e02dfd4088c7030abbf5008eb0a092c8
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/EntityScheduler.java
@@ -0,0 +1,181 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.util.Validate;
+import io.papermc.paper.util.TickThread;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import net.minecraft.world.entity.Entity;
+import org.bukkit.craftbukkit.entity.CraftEntity;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+
+/**
+ * An entity can move between worlds with an arbitrary tick delay, be temporarily removed
+ * for players (i.e end credits), be partially removed from world state (i.e inactive but not removed),
+ * teleport between ticking regions, teleport between worlds (which will change the underlying Entity object
+ * for non-players), and even be removed entirely from the server. The uncertainty of an entity's state can make
+ * it difficult to schedule tasks without worrying about undefined behaviors resulting from any of the states listed
+ * previously.
+ *
+ * <p>
+ * This class is designed to eliminate those states by providing an interface to run tasks only when an entity
+ * is contained in a world, on the owning thread for the region, and by providing the current Entity object.
+ * The scheduler also allows a task to provide a callback, the "retired" callback, that will be invoked
+ * if the entity is removed before a task that was scheduled could be executed. The scheduler is also
+ * completely thread-safe, allowing tasks to be scheduled from any thread context. The scheduler also indicates
+ * properly whether a task was scheduled successfully (i.e scheduler not retired), thus the code scheduling any task
+ * knows whether the given callbacks will be invoked eventually or not - which may be critical for off-thread
+ * contexts.
+ * </p>
+ */
+public final class EntityScheduler {
+
+    /**
+     * The Entity. Note that it is the CraftEntity, since only that class properly tracks world transfers.
+     */
+    public final CraftEntity entity;
+
+    private static final record ScheduledTask(Consumer<? extends Entity> run, Consumer<? extends Entity> retired) {}
+
+    private long tickCount = 0L;
+    private static final long RETIRED_TICK_COUNT = -1L;
+    private final Object stateLock = new Object();
+    private final Long2ObjectOpenHashMap<List<ScheduledTask>> oneTimeDelayed = new Long2ObjectOpenHashMap<>();
+
+    private final ArrayDeque<ScheduledTask> currentlyExecuting = new ArrayDeque<>();
+
+    public EntityScheduler(final CraftEntity entity) {
+        this.entity = Validate.notNull(entity);
+    }
+
+    /**
+     * Retires the scheduler, preventing new tasks from being scheduled and invoking the retired callback
+     * on all currently scheduled tasks.
+     *
+     * <p>
+     * Note: This should only be invoked after synchronously removing the entity from the world.
+     * </p>
+     *
+     * @throws IllegalStateException If the scheduler is already retired.
+     */
+    public void retire() {
+        synchronized (this.stateLock) {
+            if (this.tickCount == RETIRED_TICK_COUNT) {
+                throw new IllegalStateException("Already retired");
+            }
+            this.tickCount = RETIRED_TICK_COUNT;
+        }
+
+        final Entity thisEntity = this.entity.getHandle();
+
+        // correctly handle and order retiring while running executeTick
+        for (int i = 0, len = this.currentlyExecuting.size(); i < len; ++i) {
+            final ScheduledTask task = this.currentlyExecuting.pollFirst();
+            final Consumer<Entity> retireTask = (Consumer<Entity>)task.retired;
+            if (retireTask == null) {
+                continue;
+            }
+
+            retireTask.accept(thisEntity);
+        }
+
+        for (final List<ScheduledTask> tasks : this.oneTimeDelayed.values()) {
+            for (int i = 0, len = tasks.size(); i < len; ++i) {
+                final ScheduledTask task = tasks.get(i);
+                final Consumer<Entity> retireTask = (Consumer<Entity>)task.retired;
+                if (retireTask == null) {
+                    continue;
+                }
+
+                retireTask.accept(thisEntity);
+            }
+        }
+    }
+
+    /**
+     * Schedules a task with the given delay. If the task failed to schedule because the scheduler is retired (entity
+     * removed), then returns {@code false}. Otherwise, either the run callback will be invoked after the specified delay,
+     * or the retired callback will be invoked if the scheduler is retired.
+     * Note that the retired callback is invoked in critical code, so it should not attempt to remove the entity, remove
+     * other entities, load chunks, load worlds, modify ticket levels, etc.
+     *
+     * <p>
+     * It is guaranteed that the run and retired callback are invoked on the region which owns the entity.
+     * </p>
+     * <p>
+     * The run and retired callback take an Entity parameter representing the current object entity that the scheduler
+     * is tied to. Since the scheduler is transferred when an entity changes dimensions, it is possible the entity parameter
+     * is not the same when the task was first scheduled. Thus, <b>only</b> the parameter provided should be used.
+     * </p>
+     * @param run The callback to run after the specified delay, may not be null.
+     * @param retired Retire callback to run if the entity is retired before the run callback can be invoked, may be null.
+     * @param delay The delay in ticks before the run callback is invoked. Any value less-than 1 is treated as 1.
+     * @return {@code true} if the task was scheduled, which means that either the run function or the retired function
+     *         will be invoked (but never both), or {@code false} indicating neither the run nor retired function will be invoked
+     *         since the scheduler has been retired.
+     */
+    public boolean schedule(final Consumer<? extends Entity> run, final Consumer<? extends Entity> retired, final long delay) {
+        Validate.notNull(run, "Run task may not be null");
+
+        final ScheduledTask task = new ScheduledTask(run, retired);
+        synchronized (this.stateLock) {
+            if (this.tickCount == RETIRED_TICK_COUNT) {
+                return false;
+            }
+            this.oneTimeDelayed.computeIfAbsent(this.tickCount + Math.max(1L, delay), (final long keyInMap) -> {
+                return new ArrayList<>();
+            }).add(task);
+        }
+
+        return true;
+    }
+
+    /**
+     * Executes a tick for the scheduler.
+     *
+     * @throws IllegalStateException If the scheduler is retired.
+     */
+    public void executeTick() {
+        final Entity thisEntity = this.entity.getHandle();
+
+        TickThread.ensureTickThread(thisEntity, "May not tick entity scheduler asynchronously");
+        final List<ScheduledTask> toRun;
+        synchronized (this.stateLock) {
+            if (this.tickCount == RETIRED_TICK_COUNT) {
+                throw new IllegalStateException("Ticking retired scheduler");
+            }
+            ++this.tickCount;
+            if (this.oneTimeDelayed.isEmpty()) {
+                toRun = null;
+            } else {
+                toRun = this.oneTimeDelayed.remove(this.tickCount);
+            }
+        }
+
+        if (toRun != null) {
+            for (int i = 0, len = toRun.size(); i < len; ++i) {
+                this.currentlyExecuting.addLast(toRun.get(i));
+            }
+        }
+
+        // Note: It is allowed for the tasks executed to retire the entity in a given task.
+        for (int i = 0, len = this.currentlyExecuting.size(); i < len; ++i) {
+            if (!TickThread.isTickThreadFor(thisEntity)) {
+                // tp has been queued sync by one of the tasks
+                // in this case, we need to delay the tasks for next tick
+                break;
+            }
+            final ScheduledTask task = this.currentlyExecuting.pollFirst();
+
+            if (this.tickCount != RETIRED_TICK_COUNT) {
+                ((Consumer<Entity>)task.run).accept(thisEntity);
+            } else {
+                // retired synchronously
+                // note: here task is null
+                break;
+            }
+        }
+    }
+}
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..70c3accbab4e69268435c6f4fb13d29c7662283d
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionShutdownThread.java
@@ -0,0 +1,112 @@
+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.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();
+
+    ThreadedRegioniser.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 ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> getRegion() {
+        final Thread currentThread = Thread.currentThread();
+        if (currentThread instanceof RegionShutdownThread shutdownThread) {
+            return shutdownThread.shuttingDown;
+        }
+        return null;
+    }
+
+
+    static RegionisedWorldData 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();
+        } catch (final Throwable thr) {
+            LOGGER.error("Failed to save level data for " + world.getWorld().getName(), thr);
+        }
+    }
+
+    private void saveRegionChunks(final ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region,
+                                  final boolean first, final boolean last) {
+        final ChunkPos center = region.getCenterChunk();
+        LOGGER.info("Saving chunks around region around chunk " + center + " in world '" + region.regioniser.world.getWorld().getName() + "'");
+        try {
+            this.shuttingDown = region;
+            region.regioniser.world.chunkTaskScheduler.chunkHolderManager.close(true, true, first, 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 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.warn("Scheduler halted");
+        } else {
+            LOGGER.warn("Scheduler did not terminate within 60s, proceeding with shutdown anyways");
+        }
+
+        MinecraftServer.getServer().stopServer(); // stop part 1: most logic, kicking players, plugins, etc
+        for (final ServerLevel world : MinecraftServer.getServer().getAllLevels()) {
+            final List<ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>>
+                regions = new ArrayList<>();
+            world.regioniser.computeForAllRegionsUnsynchronised(regions::add);
+
+            for (int i = 0, len = regions.size(); i < len; ++i) {
+                final ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region = regions.get(i);
+                this.saveRegionChunks(region, i == 0, (i + 1) == len);
+            }
+
+            if (regions.isEmpty()) {
+                // still need to halt the chunk system
+                this.haltWorldNoRegions(world);
+            }
+
+            this.saveLevelData(world);
+        }
+        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/RegionisedData.java b/src/main/java/io/papermc/paper/threadedregions/RegionisedData.java
new file mode 100644
index 0000000000000000000000000000000000000000..3549e5f3359f38b207e189d89595442018c9dfa2
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionisedData.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 RegionisedData} 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 RegionisedData} 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 RegionisedData}'s world. Consider the usages of {@code RegionisedData} 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 RegionisedData<EntityTickList> entityTickLists =
+ *                 new RegionisedData<>(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 RegionisedData 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 RegionisedData object
+ *             // is not instantiated per world, but rather globally.
+ *             public final RegionisedData<TickTimes> tickTimes =
+ *                  new RegionisedData<>(null, () -> new TickTimes(), ...);
+ *         }
+ *         }
+ *     </pre>
+ *     In general, it is advised that if a RegionisedData 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 RegionisedData<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 RegionisedData(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 RegionisedData}'s world is not {@code null},
+     *                               and the current ticking region's world does not match this {@code RegionisedData}'s world.
+     */
+    public @Nullable T get() {
+        final ThreadedRegioniser.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().getOrCreateRegionisedData(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/RegionisedServer.java b/src/main/java/io/papermc/paper/threadedregions/RegionisedServer.java
new file mode 100644
index 0000000000000000000000000000000000000000..269c051e20cd07e692c624a873e4ee2b5ae5589a
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionisedServer.java
@@ -0,0 +1,366 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue;
+import ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool;
+import com.mojang.authlib.GameProfile;
+import com.mojang.logging.LogUtils;
+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.game.ClientboundDisconnectPacket;
+import net.minecraft.network.protocol.status.ServerStatus;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.dedicated.DedicatedServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import net.minecraft.server.network.ServerLoginPacketListenerImpl;
+import net.minecraft.server.players.PlayerList;
+import net.minecraft.util.Mth;
+import net.minecraft.world.level.GameRules;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import org.slf4j.Logger;
+import java.util.ArrayList;
+import java.util.Arrays;
+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 RegionisedServer {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+    private static final RegionisedServer INSTANCE = new RegionisedServer();
+
+    public final RegionisedTaskQueue taskQueue = new RegionisedTaskQueue();
+
+    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 RegionisedServer getInstance() {
+        return INSTANCE;
+    }
+
+    public void addConnection(final Connection conn) {
+        this.connections.add(conn);
+    }
+
+    private boolean removeConnection(final Connection conn) {
+        return this.connections.remove(conn);
+    }
+
+    public void addWorld(final ServerLevel world) {
+        this.worlds.add(world);
+    }
+
+    public void init() {
+        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 ThreadedRegioniser.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 RegionisedServer server;
+
+        private final AtomicBoolean scheduled = new AtomicBoolean();
+        private final AtomicBoolean ticking = new AtomicBoolean();
+
+        public GlobalTickTickHandle(final RegionisedServer 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 void globalTick(final int tickCount) {
+        ++this.tickCount;
+        // 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 ServerStatus status = mcServer.getStatus();
+        final PlayerList playerList = mcServer.getPlayerList();
+
+        final long i = 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 (i - this.lastServerStatus >= 5000000000L) {
+            this.lastServerStatus = i;
+            List<ServerPlayer> players = new ArrayList<>(playerList.players);
+            ServerStatus.Players newPlayers = new ServerStatus.Players(mcServer.getMaxPlayers(), players.size());
+
+            if (!mcServer.hidesOnlinePlayers()) {
+                GameProfile[] agameprofile = new GameProfile[Math.min(players.size(), org.spigotmc.SpigotConfig.playerSample)]; // Paper
+                int j = Mth.nextInt(new LegacyRandomSource(i), 0, players.size() - agameprofile.length);
+
+                for (int k = 0; k < agameprofile.length; ++k) {
+                    ServerPlayer entityplayer = (ServerPlayer) players.get(j + k);
+
+                    if (entityplayer.allowsListing()) {
+                        agameprofile[k] = entityplayer.getGameProfile();
+                    } else {
+                        agameprofile[k] = MinecraftServer.ANONYMOUS_PLAYER_PROFILE;
+                    }
+                }
+
+                Collections.shuffle(Arrays.asList(agameprofile));
+                newPlayers.setSample(agameprofile);
+            }
+            // TODO make players field volatile
+            status.setPlayers(newPlayers);
+        }
+    }
+
+    private boolean hasConnectionMovedToMain(final Connection conn) {
+        final PacketListener packetListener = conn.getPacketListener();
+
+        return (packetListener instanceof ServerGamePacketListenerImpl) ||
+            (packetListener instanceof ServerLoginPacketListenerImpl loginListener && loginListener.state.ordinal() >= ServerLoginPacketListenerImpl.State.HANDING_OFF.ordinal());
+    }
+
+    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 (this.hasConnectionMovedToMain(conn)) {
+                if (!conn.isConnected()) {
+                    this.removeConnection(conn);
+                }
+                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 {}", io.papermc.paper.configuration.GlobalConfiguration.get().logging.logPlayerIpAddresses ? String.valueOf(conn.getRemoteAddress()) : "<ip address withheld>", exception); // Paper
+                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();
+    }
+
+    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/RegionisedTaskQueue.java b/src/main/java/io/papermc/paper/threadedregions/RegionisedTaskQueue.java
new file mode 100644
index 0000000000000000000000000000000000000000..c13237edb7323fa747d260375f626a5c9979b004
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionisedTaskQueue.java
@@ -0,0 +1,742 @@
+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.io.RegionFileIOThread;
+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.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.ReentrantLock;
+
+public final class RegionisedTaskQueue {
+
+    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 SWMRLong2ObjectHashTable<AtomicLong> referenceCounters = new SWMRLong2ObjectHashTable<>();
+
+        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 ThreadedRegioniser<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regioniser = this.world.regioniser;
+            final ThreadedRegioniser.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
+            );
+        }
+
+        private void decrementReference(final AtomicLong reference, final long coord) {
+            final long val = reference.decrementAndGet();
+            if (val == 0L) {
+                final ReentrantLock ticketLock = this.world.chunkTaskScheduler.chunkHolderManager.ticketLock;
+                ticketLock.lock();
+                try {
+                    if (this.referenceCounters.remove(coord, reference)) {
+                        WorldRegionTaskData.this.removeTicket(coord);
+                    } // else: race condition, something replaced our reference - not our issue anymore
+                } finally {
+                    ticketLock.unlock();
+                }
+            } else if (val < 0L) {
+                throw new IllegalStateException("Reference count < 0: " + val);
+            }
+        }
+
+        private AtomicLong incrementReference(final long coord) {
+            final AtomicLong ret = this.referenceCounters.get(coord);
+            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 ReentrantLock ticketLock = this.world.chunkTaskScheduler.chunkHolderManager.ticketLock;
+            ticketLock.lock();
+            try {
+                final AtomicLong replace = new AtomicLong(1L);
+                final AtomicLong valueInMap = this.referenceCounters.putIfAbsent(coord, replace);
+                if (valueInMap == null) {
+                    // replaced, we should usually be here
+                    this.addTicket(coord);
+                    return replace;
+                } // else: need to attempt to acquire the reference
+
+                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(coord, replace);
+                        return replace;
+                    }
+
+                    for (int i = 0; i < failures; ++i) {
+                        ConcurrentUtil.backoff();
+                    }
+
+                    if (curr == (curr = valueInMap.compareAndExchange(curr, curr + 1L))) {
+                        // acquired
+                        return valueInMap;
+                    }
+
+                    ++failures;
+                }
+            } finally {
+                ticketLock.unlock();
+            }
+        }
+    }
+
+    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 ThreadedRegioniser<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regioniser,
+                   final Long2ReferenceOpenHashMap<ThreadedRegioniser.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);
+        }
+
+        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;
+                synchronized (target) {
+                    mergeInto(target, this.queues);
+                }
+            }
+        }
+
+        private static void mergeInto(final PrioritisedQueue target, final ArrayDeque<ChunkBasedPriorityTask>[] thisQueues) {
+            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 ThreadedRegioniser<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> regioniser,
+                          final Long2ReferenceOpenHashMap<ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>> into) {
+            final Reference2ReferenceOpenHashMap<ThreadedRegioniser.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 ThreadedRegioniser.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<ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, ArrayDeque<ChunkBasedPriorityTask>[]>>
+                     iterator = split.reference2ReferenceEntrySet().fastIterator();
+                     iterator.hasNext();) {
+                    final Reference2ReferenceMap.Entry<ThreadedRegioniser.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
+                            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/RegionisedWorldData.java b/src/main/java/io/papermc/paper/threadedregions/RegionisedWorldData.java
new file mode 100644
index 0000000000000000000000000000000000000000..8317638bdb40764c389a68ced176e6d334eeb599
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/RegionisedWorldData.java
@@ -0,0 +1,664 @@
+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 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.game.ClientboundDisconnectPacket;
+import net.minecraft.server.level.ChunkHolder;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import net.minecraft.util.Mth;
+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.block.Block;
+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.gameevent.GameEvent;
+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.phys.Vec3;
+import net.minecraft.world.ticks.LevelTicks;
+import org.bukkit.craftbukkit.block.CraftBlockState;
+import org.bukkit.craftbukkit.util.UnsafeList;
+import org.bukkit.entity.SpawnCategory;
+import org.slf4j.Logger;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+public final class RegionisedWorldData {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    public static final RegionisedData.RegioniserCallback<RegionisedWorldData> REGION_CALLBACK = new RegionisedData.RegioniserCallback<>() {
+        @Override
+        public void merge(final RegionisedWorldData from, final RegionisedWorldData into, final long fromTickOffset) {
+            // connections
+            for (final Connection conn : from.connections) {
+                into.connections.add(conn);
+            }
+            // time
+            final long fromRedstoneTimeOffset = from.redstoneTime - into.redstoneTime;
+            // entities
+            for (final ServerPlayer player : from.localPlayers) {
+                into.localPlayers.add(player);
+            }
+            for (final Entity entity : from.allEntities) {
+                into.allEntities.add(entity);
+                entity.updateTicks(fromTickOffset, fromRedstoneTimeOffset);
+            }
+            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 ChunkHolder holder : from.needsChangeBroadcasting) {
+                into.needsChangeBroadcasting.add(holder);
+            }
+            // 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 RegionisedWorldData from, final int chunkToRegionShift,
+                          final Long2ReferenceOpenHashMap<RegionisedWorldData> regionToData,
+                          final ReferenceOpenHashSet<RegionisedWorldData> 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.
+                regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift))
+                    .localPlayers.add(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 RegionisedWorldData 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: 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 RegionisedWorldData 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<RegionisedWorldData>> iterator = regionToData.long2ReferenceEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Long2ReferenceMap.Entry<RegionisedWorldData> entry = iterator.next();
+                final long key = entry.getLongKey();
+                final RegionisedWorldData 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 RegionisedWorldData 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 RegionisedWorldData 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 RegionisedWorldData regionisedWorldData : dataSet) {
+                regionisedWorldData.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 ChunkHolder holder : from.needsChangeBroadcasting) {
+                final ChunkPos pos = holder.pos;
+
+                regionToData.get(CoordinateUtils.getChunkKey(pos.x >> chunkToRegionShift, pos.z >> chunkToRegionShift))
+                    .needsChangeBroadcasting.add(holder);
+            }
+            // 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 RegionisedWorldData 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 RegionisedWorldData regionisedWorldData : dataSet) {
+                regionisedWorldData.catSpawnerNextTick = from.catSpawnerNextTick;
+                regionisedWorldData.patrolSpawnerNextTick = from.patrolSpawnerNextTick;
+                regionisedWorldData.phantomSpawnerNextTick = from.phantomSpawnerNextTick;
+                regionisedWorldData.wanderingTraderTickDelay = from.wanderingTraderTickDelay;
+                regionisedWorldData.wanderingTraderSpawnChance = from.wanderingTraderSpawnChance;
+                regionisedWorldData.wanderingTraderSpawnDelay = from.wanderingTraderSpawnDelay;
+                regionisedWorldData.villageSiegeState = new VillageSiegeState(); // just re set it, as the spawn pos will be invalid
+            }
+        }
+    };
+
+    public final ServerLevel world;
+
+    private RegionisedServer.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 ReferenceList<Entity> allEntities = 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 ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new ReferenceOpenHashSet<>();
+
+    // 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
+
+    // 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;
+    }
+
+    public RegionisedWorldData(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);
+
+        // tasks may be drained before the region ticks, so we must set up the tick data early just in case
+        this.updateTickData();
+    }
+
+    public RegionisedServer.WorldLevelData getTickData() {
+        return this.tickData;
+    }
+
+    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
+    }
+
+    // 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();
+                this.connections.remove(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.getLevel().chunkSource.removeTicketAtLevel(
+                    ServerGamePacketListenerImpl.DISCONNECT_TICKET, player.connection.disconnectPos,
+                    ChunkHolderManager.MAX_TICKET_LEVEL,
+                    player.connection.disconnectTicketId
+                );
+                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 {}", io.papermc.paper.configuration.GlobalConfiguration.get().logging.logPlayerIpAddresses ? String.valueOf(conn.getRemoteAddress()) : "<ip address withheld>", exception); // Paper
+                MutableComponent ichatmutablecomponent = Component.literal("Internal server error");
+
+                conn.send(new ClientboundDisconnectPacket(ichatmutablecomponent), PacketSendListener.thenRun(() -> {
+                    conn.disconnect(ichatmutablecomponent);
+                }));
+                conn.setReadOnly();
+                continue;
+            }
+        }
+    }
+
+    // entities hooks
+    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 addEntityTickingEntity(final Entity entity) {
+        if (!TickThread.isTickThreadFor(entity)) {
+            throw new IllegalArgumentException("Entity " + entity + " is not under this region's control");
+        }
+        this.entityTickList.add(entity);
+    }
+
+    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);
+    }
+
+    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);
+            }
+        }
+    }
+
+    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);
+            }
+        }
+    }
+
+    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 addEntityTickingChunks(final LevelChunk levelChunk) {
+        this.entityTickingChunks.add(levelChunk);
+    }
+
+    public void removeEntityTickingChunk(final LevelChunk levelChunk) {
+        this.entityTickingChunks.remove(levelChunk);
+    }
+
+    public IteratorSafeOrderedReferenceSet<LevelChunk> getEntityTickingChunks() {
+        return this.entityTickingChunks;
+    }
+
+    public void addChunkHolderNeedsBroadcasting(final ChunkHolder holder) {
+        this.needsChangeBroadcasting.add(holder);
+    }
+
+    public void removeChunkHolderNeedsBroadcasting(final ChunkHolder holder) {
+        this.needsChangeBroadcasting.remove(holder);
+    }
+
+    public ReferenceOpenHashSet<ChunkHolder> getNeedsChangeBroadcasting() {
+        return this.needsChangeBroadcasting;
+    }
+}
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..84b4ff07735fb84e28ee8966ffdedb1bb3d07dff
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/TeleportUtils.java
@@ -0,0 +1,60 @@
+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) {
+                    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) -> {
+                        onComplete.accept(null);
+                    },
+                    1L
+                );
+                if (!scheduled) {
+                    onComplete.accept(null);
+                }
+            }
+        );
+
+        final boolean scheduled = to.getBukkitEntity().taskScheduler.schedule(
+            (final Entity target) -> {
+                positionCompletable.complete(target.getBukkitEntity().getLocation());
+            },
+            (final Entity retired) -> {
+                onComplete.accept(null);
+            },
+            1L
+        );
+        if (!scheduled) {
+            onComplete.accept(null);
+        }
+    }
+
+    private TeleportUtils() {}
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/ThreadedRegioniser.java b/src/main/java/io/papermc/paper/threadedregions/ThreadedRegioniser.java
new file mode 100644
index 0000000000000000000000000000000000000000..f05546aa9124d4c0e34005f528483bf516e93c20
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/ThreadedRegioniser.java
@@ -0,0 +1,1187 @@
+package io.papermc.paper.threadedregions;
+
+import ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue;
+import ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable;
+import ca.spottedleaf.concurrentutil.util.ConcurrentUtil;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+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.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 java.io.FileReader;
+import java.lang.invoke.VarHandle;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.StampedLock;
+import java.util.function.Consumer;
+
+public final class ThreadedRegioniser<R extends ThreadedRegioniser.ThreadedRegionData<R, S>, S extends ThreadedRegioniser.ThreadedRegionSectionData> {
+
+    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<>();
+     */
+
+    public ThreadedRegioniser(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);
+        }
+    }
+     */
+
+    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 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 need to create it
+
+            // 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);
+                }
+            }
+
+            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;
+                    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
+
+                boolean delayedTrueMerge = false;
+
+                for (final ThreadedRegion<R, S> region : nearbyRegions) {
+                    if (region == regionOfInterest) {
+                        continue;
+                    }
+                    // need the relaxed check, as the region may already be
+                    // a merge target
+                    if (!region.tryKill()) {
+                        regionOfInterest.mergeIntoLater(region);
+                        delayedTrueMerge = true;
+                    } else {
+                        region.mergeInto(regionOfInterest);
+                    }
+                }
+
+                if (delayedTrueMerge && firstUnlockedRegion != null) {
+                    // we need to retire this region, as it can no longer tick
+                    if (regionOfInterest.state == ThreadedRegion.STATE_STEADY_STATE) {
+                        regionOfInterest.state = ThreadedRegion.STATE_NOT_READY;
+                        this.callbacks.onRegionInactive(regionOfInterest);
+                    }
+                }
+
+                // need to set alive if we created it and we didn't delay a merge
+                regionOfInterestAlive = firstUnlockedRegion == null && !delayedTrueMerge && regionOfInterest.mergeIntoLater.isEmpty() && regionOfInterest.expectingMergeFrom.isEmpty();
+            }
+
+            if (regionOfInterestAlive) {
+                regionOfInterest.state = ThreadedRegion.STATE_STEADY_STATE;
+                if (!regionOfInterest.mergeIntoLater.isEmpty() || !regionOfInterest.expectingMergeFrom.isEmpty()) {
+                    throw new IllegalStateException("Should not happen on region " + this);
+                }
+                this.callbacks.onRegionActive(regionOfInterest);
+            }
+        } 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();
+                }
+            }
+        } 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.tryKill()) {
+                    throw new IllegalStateException("Merge from region " + mergeFrom + " should be killable! Trying to merge into " + region);
+                }
+                mergeFrom.mergeInto(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_NOT_READY;
+                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) {
+            region.state = ThreadedRegion.STATE_STEADY_STATE;
+            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_STEADY_STATE;
+            if (!region.expectingMergeFrom.isEmpty() || !region.mergeIntoLater.isEmpty()) {
+                throw new IllegalStateException("Illegal state " + region);
+            }
+            return;
+        }
+
+        // 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<>();
+
+        for (final List<ThreadedRegionSection<R, S>> sections : newRegions) {
+            final ThreadedRegion<R, S> newRegion = new ThreadedRegion<>(this);
+            newRegionsSet.add(newRegion);
+
+            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_STEADY_STATE;
+            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_NOT_READY     = 0;
+        private static final int STATE_STEADY_STATE  = 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 ThreadedRegioniser<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 ThreadedRegioniser<R, S> regioniser) {
+            this.regioniser = regioniser;
+            this.id = REGION_ID_GENERATOR.getAndIncrement();
+            this.state = STATE_NOT_READY;
+            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();
+                }
+            }
+        }
+
+        public ChunkPos getCenterChunk() {
+            final LongArrayList sections = this.getOwnedSections();
+
+            sections.sort(null);
+
+            // note: regions always have at least one section
+            final long middle = sections.getLong(sections.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);
+            }
+        }
+
+        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_NOT_READY: {
+                    this.state = STATE_DEAD;
+                    this.onRemove(false);
+                    return true;
+                }
+                case STATE_STEADY_STATE: {
+                    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() {
+            this.regioniser.acquireWriteLock();
+            try {
+                if (this.state != STATE_STEADY_STATE) {
+                    return false;
+                }
+
+                if (!this.mergeIntoLater.isEmpty() || !this.expectingMergeFrom.isEmpty()) {
+                    throw new IllegalStateException("Region " + this + " should not be steady state");
+                }
+
+                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_STEADY_STATE;
+            } 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 ThreadedRegioniser<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 ThreadedRegioniser<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 ThreadedRegioniser<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 ThreadedRegioniser<R, S> regioniser,
+                                      final int nonEmptyNeighbours) {
+            this(sectionX, sectionZ, regioniser);
+
+            this.nonEmptyNeighbours = nonEmptyNeighbours;
+        }
+
+        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 ThreadedRegioniser<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);
+    }
+}
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..e75aac237764c7a9fa0538ddf8d68b1e14de7d49
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/TickRegionScheduler.java
@@ -0,0 +1,544 @@
+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.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());
+                return ret;
+            }
+        });
+    }
+
+    public int getTotalThreadCount() {
+        return this.scheduler.getThreads().length;
+    }
+
+    private static void setTickingRegion(final ThreadedRegioniser.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.currentTickingWorldRegionisedData = region.regioniser.world.worldRegionData.get();
+        } else {
+            tickThreadRunner.currentTickingWorldRegionisedData = 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 ThreadedRegioniser.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 RegionisedData#get()} method.
+     * If this thread is not a TickThread, then returns {@code null}.
+     */
+    public static RegionisedWorldData getCurrentRegionisedWorldData() {
+        final Thread currThread = Thread.currentThread();
+        if (!(currThread instanceof TickThreadRunner tickThreadRunner)) {
+            return RegionShutdownThread.getWorldData();
+        }
+        return tickThreadRunner.currentTickingWorldRegionisedData;
+    }
+
+    /**
+     * 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);
+    }
+
+    public void setHasTasks(final RegionScheduleHandle region) {
+        this.scheduler.notifyTasks(region);
+    }
+
+    public void init() {
+        this.scheduler.start();
+    }
+
+    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();
+
+        LOGGER.error("Region #" + (handle.region == null ? -1L : handle.region.id) + " centered at chunk " + center + " 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 ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> currentTickingRegion;
+        private RegionisedWorldData currentTickingWorldRegionisedData;
+        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);
+        }
+
+        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 {
+                TickRegionScheduler.setTickTask(null);
+                if (this.region != null) {
+                    TickRegionScheduler.setTickingRegion(null);
+                }
+                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);
+            }
+
+            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 {
+                TickRegionScheduler.setTickTask(null);
+                if (this.region != null) {
+                    TickRegionScheduler.setTickingRegion(null);
+                }
+                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);
+            }
+
+            // Only AFTER updating the tickStart
+            return this.markNotTicking() && !this.cancelled.get();
+        }
+
+        /**
+         * Only safe to call if this tick data matches the current ticking region.
+         */
+        private 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
new file mode 100644
index 0000000000000000000000000000000000000000..c17669c1e98cd954643fa3b988c12b4b6c3b174e
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/TickRegions.java
@@ -0,0 +1,340 @@
+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.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.AtomicLong;
+import java.util.function.BooleanSupplier;
+
+public final class TickRegions implements ThreadedRegioniser.RegionCallbacks<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> {
+
+    private static final Logger LOGGER = LogUtils.getLogger();
+
+    public static int getRegionChunkShift() {
+        return 4;
+    }
+
+    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 tickThreads;
+        if (config.threads <= 0) {
+            tickThreads = Runtime.getRuntime().availableProcessors() / 2;
+            if (tickThreads <= 4) {
+                tickThreads = 1;
+            } else {
+                tickThreads = (2 * tickThreads) / 3;
+            }
+        } else {
+            tickThreads = config.threads;
+        }
+
+        scheduler = new TickRegionScheduler(tickThreads);
+        LOGGER.info("Regionised ticking is enabled with " + tickThreads + " tick threads");
+    }
+
+    @Override
+    public TickRegionData createNewData(final ThreadedRegioniser.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 ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        // nothing for now
+    }
+
+    @Override
+    public void onRegionDestroy(final ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        // nothing for now
+    }
+
+    @Override
+    public void onRegionActive(final ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+        final TickRegionData data = region.getData();
+
+        data.tickHandle.checkInitialSchedule();
+        scheduler.scheduleRegion(data.tickHandle);
+    }
+
+    @Override
+    public void onRegionInactive(final ThreadedRegioniser.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();
+    }
+
+    public static final class TickRegionSectionData implements ThreadedRegioniser.ThreadedRegionSectionData {}
+
+    public static final class TickRegionData implements ThreadedRegioniser.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 ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region;
+        public final ServerLevel world;
+
+        // generic regionised data
+        private final Reference2ReferenceOpenHashMap<RegionisedData<?>, Object> regionisedData = new Reference2ReferenceOpenHashMap<>();
+
+        // tick data
+        private ConcreteRegionTickHandle tickHandle = new ConcreteRegionTickHandle(this, SchedulerThreadPool.DEADLINE_NOT_SET);
+
+        // queue data
+        private final RegionisedTaskQueue.RegionTaskQueueData taskQueueData;
+
+        // chunk holder manager data
+        private final ChunkHolderManager.HolderManagerRegionData holderManagerRegionData = new ChunkHolderManager.HolderManagerRegionData();
+
+        private TickRegionData(final ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region) {
+            this.region = region;
+            this.world = region.regioniser.world;
+            this.taskQueueData = new RegionisedTaskQueue.RegionTaskQueueData(this.world.taskQueueRegionData);
+        }
+
+        public RegionisedTaskQueue.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 getOrCreateRegionisedData(final RegionisedData<T> regionisedData) {
+            T ret = (T)this.regionisedData.get(regionisedData);
+
+            if (ret != null) {
+                return ret;
+            }
+
+            ret = regionisedData.createNewValue();
+            this.regionisedData.put(regionisedData, ret);
+
+            return ret;
+        }
+
+        @Override
+        public void split(final ThreadedRegioniser<TickRegionData, TickRegionSectionData> regioniser,
+                          final Long2ReferenceOpenHashMap<ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData>> into,
+                          final ReferenceOpenHashSet<ThreadedRegioniser.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 ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region : regions) {
+                final TickRegionData data = region.getData();
+                data.tickHandle.copyDeadlineAndTickCount(this.tickHandle);
+            }
+
+            // generic regionised data
+            for (final Iterator<Reference2ReferenceMap.Entry<RegionisedData<?>, Object>> dataIterator = this.regionisedData.reference2ReferenceEntrySet().fastIterator();
+                 dataIterator.hasNext();) {
+                final Reference2ReferenceMap.Entry<RegionisedData<?>, Object> regionDataEntry = dataIterator.next();
+                final RegionisedData<?> data = regionDataEntry.getKey();
+                final Object from = regionDataEntry.getValue();
+
+                final ReferenceOpenHashSet<Object> dataSet = new ReferenceOpenHashSet<>(regions.size(), 0.75f);
+
+                for (final ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region : regions) {
+                    dataSet.add(region.getData().getOrCreateRegionisedData(data));
+                }
+
+                final Long2ReferenceOpenHashMap<Object> regionToData = new Long2ReferenceOpenHashMap<>(into.size(), 0.75f);
+
+                for (final Iterator<Long2ReferenceMap.Entry<ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData>>> regionIterator = into.long2ReferenceEntrySet().fastIterator();
+                     regionIterator.hasNext();) {
+                    final Long2ReferenceMap.Entry<ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData>> entry = regionIterator.next();
+                    final ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData> region = entry.getValue();
+                    final Object to = region.getData().getOrCreateRegionisedData(data);
+
+                    regionToData.put(entry.getLongKey(), to);
+                }
+
+                ((RegionisedData<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 ThreadedRegioniser.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<ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData>>> regionIterator = into.long2ReferenceEntrySet().fastIterator();
+                     regionIterator.hasNext();) {
+                    final Long2ReferenceMap.Entry<ThreadedRegioniser.ThreadedRegion<TickRegionData, TickRegionSectionData>> entry = regionIterator.next();
+                    final ThreadedRegioniser.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 ThreadedRegioniser.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<RegionisedData<?>, Object>> iterator = this.regionisedData.reference2ReferenceEntrySet().fastIterator();
+                 iterator.hasNext();) {
+                final Reference2ReferenceMap.Entry<RegionisedData<?>, Object> entry = iterator.next();
+                final RegionisedData<?> regionisedData = entry.getKey();
+                final Object from = entry.getValue();
+                final Object to = into.getData().getOrCreateRegionisedData(regionisedData);
+
+                ((RegionisedData<Object>)regionisedData).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();
+        }
+
+        @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 RegionisedTaskQueue.RegionTaskQueueData queue = this.region.taskQueueData;
+            boolean executeChunkTask = true;
+            boolean executeTickTask = true;
+            do {
+                if (executeTickTask) {
+                    executeTickTask = queue.executeTickTask();
+                }
+                if (executeChunkTask) {
+                    executeChunkTask = queue.executeChunkTask();
+                }
+            } while ((executeChunkTask | executeTickTask) && canContinue.getAsBoolean());
+            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..4889ebf6e3eb5901eeac49900c541d2359d71316
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/commands/CommandServerHealth.java
@@ -0,0 +1,330 @@
+package io.papermc.paper.threadedregions.commands;
+
+import io.papermc.paper.threadedregions.ThreadedRegioniser;
+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 DecimalFormat TWO_DECIMAL_PLACES = new DecimalFormat("#0.00");
+    private static final DecimalFormat ONE_DECIMAL_PLACES = new DecimalFormat("#0.0");
+
+    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("/<cmd> [server/region] [lowest regions to display]");
+        this.setDescription("Reports information about server health.");
+        this.setPermission("bukkit.command.tps");
+    }
+
+    @Override
+    public boolean testPermissionSilent(final CommandSender target) {
+        // TODO for now
+        return true;
+    }
+
+    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.format(util * 100.0), CommandUtil.getUtilisationColourRegion(util)))
+            .append(Component.text("% util at ", PRIMARY))
+            .append(Component.text(TWO_DECIMAL_PLACES.format(mspt), CommandUtil.getColourForMSPT(mspt)))
+            .append(Component.text(" MSPT at ", PRIMARY))
+            .append(Component.text(TWO_DECIMAL_PLACES.format(tps), CommandUtil.getColourForTPS(tps)))
+            .append(Component.text(" TPS" + (newline ? "\n" : ""), PRIMARY))
+            .build();
+    }
+
+    private static boolean executeRegion(final CommandSender sender, final String commandLabel, final String[] args) {
+        final ThreadedRegioniser.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, 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<ThreadedRegioniser.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 long currTime = System.nanoTime();
+
+        final double minTps;
+        final double medianTps;
+        final double maxTps;
+        long totalTime = 0;
+        double totalUtil = 0.0;
+
+        final DoubleArrayList tpsByRegion = new DoubleArrayList();
+        final List<TickData.TickReportData> reportsByRegion = new ArrayList<>();
+
+        final int maxThreadCount = TickRegions.getScheduler().getTotalThreadCount();
+
+        for (final ThreadedRegioniser.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());
+        }
+
+        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<ThreadedRegioniser.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<ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData>, TickData.TickReportData>
+                pair = regionsBelowThreshold.get(i);
+
+            final TickData.TickReportData report = pair.right();
+            final ThreadedRegioniser.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();
+            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.format(util * 100.0), CommandUtil.getUtilisationColourRegion(util)))
+                .append(Component.text("% util at ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.format(mspt), CommandUtil.getColourForMSPT(mspt)))
+                .append(Component.text(" MSPT at ", PRIMARY))
+                .append(Component.text(TWO_DECIMAL_PLACES.format(tps), CommandUtil.getColourForTPS(tps)))
+                .append(Component.text(" TPS" + ((i + 1) == len ? "" : "\n"), PRIMARY))
+                .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.format(totalUtil * 100.0), CommandUtil.getUtilisationColourRegion(totalUtil / (double)maxThreadCount)))
+                .append(Component.text("% / ", PRIMARY))
+                .append(Component.text(ONE_DECIMAL_PLACES.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.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.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.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/commands/CommandsTPA.java b/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPA.java
new file mode 100644
index 0000000000000000000000000000000000000000..f2259d295ce613e41097819482b2084dd9c1fdd9
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPA.java
@@ -0,0 +1,138 @@
+package io.papermc.paper.threadedregions.commands;
+
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.event.ClickEvent;
+import net.kyori.adventure.text.event.HoverEvent;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.craftbukkit.entity.CraftPlayer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public final class CommandsTPA extends Command {
+
+    public CommandsTPA() {
+        super("tpa");
+        this.setUsage("/<command> <player name>");
+    }
+
+    @Override
+    public boolean testPermissionSilent(final CommandSender target) {
+        return true;
+    }
+
+    @Override
+    public boolean execute(final CommandSender sender, final String commandLabel, final String[] args) {
+        if (!(sender instanceof CraftPlayer playerSender)) {
+            sender.sendMessage(commandLabel + " only works for players");
+            return true;
+        }
+
+        if (args.length != 1) {
+            sender.sendMessage(Component.text("Usage: /" + commandLabel + " <player name>", NamedTextColor.DARK_RED));
+            return true;
+        }
+
+        final ServerPlayer target = CommandUtil.getPlayer(args[0]);
+
+        if (target == null) {
+            sender.sendMessage(
+                Component.text()
+                    .append(Component.text("Found no such player ", NamedTextColor.DARK_RED))
+                    .append(Component.text(args[0], NamedTextColor.RED))
+                    .build()
+            );
+            return true;
+        }
+
+        if (target == playerSender.getHandle()) {
+            sender.sendMessage(Component.text("Cannot tpa to yourself!", NamedTextColor.DARK_RED));
+            return true;
+        }
+
+        final String targetName = target.getGameProfile().getName();
+
+        if (!target.pendingTpas.add(playerSender.getUniqueId())) {
+            sender.sendMessage(
+                Component.text()
+                    .append(Component.text("You already have a tpa request to ", NamedTextColor.DARK_RED))
+                    .append(Component.text(targetName, NamedTextColor.RED))
+                    .build()
+            );
+            return true;
+        }
+
+        sender.sendMessage(
+            Component.text()
+                .append(Component.text("Sent tpa request to ", NamedTextColor.GRAY))
+                .append(Component.text(targetName, NamedTextColor.RED))
+                .build()
+        );
+        target.getBukkitEntity().sendMessage(
+            Component.text()
+                .append(Component.text(playerSender.getName(), NamedTextColor.RED))
+                .append(Component.text(" has requested to teleport to you!\n", NamedTextColor.GRAY))
+                .append(
+                    Component.text()
+                        .append(Component.text("Run or click ", NamedTextColor.GRAY))
+                        .append(Component.text("/tpaaccept ", NamedTextColor.DARK_GREEN))
+                        .append(Component.text(playerSender.getName(), NamedTextColor.GREEN))
+                        .append(Component.text(" to accept\n", NamedTextColor.GRAY))
+                        .build()
+                        .clickEvent(ClickEvent.runCommand("/tpaaccept " + playerSender.getName()))
+                        .hoverEvent(
+                            HoverEvent.showText(
+                                Component.text()
+                                    .append(Component.text("Click to accept tpa request from ", NamedTextColor.DARK_GREEN))
+                                    .append(Component.text(playerSender.getName(), NamedTextColor.GREEN))
+                            )
+                        )
+                )
+                .append(
+                    Component.text()
+                        .append(Component.text("Run or click ", NamedTextColor.GRAY))
+                        .append(Component.text("/tpaaccept ", NamedTextColor.DARK_RED))
+                        .append(Component.text(playerSender.getName(), NamedTextColor.RED))
+                        .append(Component.text(" to deny", NamedTextColor.GRAY))
+                        .build()
+                        .clickEvent(ClickEvent.runCommand("/tpadeny " + playerSender.getName()))
+                        .hoverEvent(
+                            HoverEvent.showText(
+                                Component.text()
+                                    .append(Component.text("Click to reject tpa request from ", NamedTextColor.DARK_RED))
+                                    .append(Component.text(playerSender.getName(), NamedTextColor.RED))
+                            )
+                        )
+                )
+                .build()
+        );
+
+        return true;
+    }
+
+    @Override
+    public List<String> tabComplete(final CommandSender sender, final String alias,
+                                    final String[] args) throws IllegalArgumentException {
+        if (!(sender instanceof CraftPlayer)) {
+            return new ArrayList<>();
+        }
+
+        final List<ServerPlayer> players = MinecraftServer.getServer().getPlayerList().players;
+
+        final Function<ServerPlayer, String> playerToName = (final ServerPlayer value) -> {
+            return value.getGameProfile().getName();
+        };
+
+        if (args.length == 0) {
+            return CommandUtil.getSortedList(players, playerToName);
+        } else if (args.length == 1) {
+            return CommandUtil.getSortedList(players, playerToName, args[0]);
+        }
+
+        return new ArrayList<>();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPAAccept.java b/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPAAccept.java
new file mode 100644
index 0000000000000000000000000000000000000000..b648d67f3ade11172af4ed76d6d14de7ca39c5d6
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPAAccept.java
@@ -0,0 +1,109 @@
+package io.papermc.paper.threadedregions.commands;
+
+import io.papermc.paper.threadedregions.TeleportUtils;
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.Entity;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.craftbukkit.entity.CraftPlayer;
+import org.bukkit.event.player.PlayerTeleportEvent;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public final class CommandsTPAAccept extends Command {
+
+    public CommandsTPAAccept() {
+        super("tpaaccept");
+        this.setUsage("/<command> <player name>");
+    }
+
+    @Override
+    public boolean testPermissionSilent(final CommandSender target) {
+        return true;
+    }
+
+    @Override
+    public boolean execute(final CommandSender sender, final String commandLabel, final String[] args) {
+        if (!(sender instanceof CraftPlayer playerSender)) {
+            sender.sendMessage(commandLabel + " only works for players");
+            return true;
+        }
+
+        if (args.length != 1) {
+            sender.sendMessage(Component.text("Usage: /" + commandLabel + " <player name>", NamedTextColor.DARK_RED));
+            return true;
+        }
+
+        final ServerPlayer target = CommandUtil.getPlayer(args[0]);
+
+        if (target == null) {
+            sender.sendMessage(
+                Component.text()
+                    .append(Component.text("Found no such player ", NamedTextColor.DARK_RED))
+                    .append(Component.text(args[0], NamedTextColor.RED))
+                    .build()
+            );
+            return true;
+        }
+
+        if (!playerSender.getHandle().pendingTpas.remove(target.getUUID())) {
+            sender.sendMessage(
+                Component.text()
+                    .append(Component.text("No tpa request to accept from ", NamedTextColor.DARK_RED))
+                    .append(Component.text(args[0], NamedTextColor.RED))
+                    .build()
+            );
+            return true;
+        }
+
+        sender.sendMessage(
+            Component.text()
+                .append(Component.text("Accepted tpa request from ", NamedTextColor.GRAY))
+                .append(Component.text(target.getGameProfile().getName(), NamedTextColor.GREEN))
+                .build()
+        );
+        target.getBukkitEntity().sendMessage(
+            Component.text()
+                .append(Component.text(playerSender.getName(), NamedTextColor.GREEN))
+                .append(Component.text(" accepted", NamedTextColor.DARK_GREEN))
+                .append(Component.text(" your tpa request!", NamedTextColor.GRAY))
+                .build()
+        );
+
+        TeleportUtils.teleport(
+            target, true, playerSender.getHandle(),
+            Float.valueOf(playerSender.getHandle().getYRot()), Float.valueOf(playerSender.getHandle().getXRot()),
+            Entity.TELEPORT_FLAG_LOAD_CHUNK | Entity.TELEPORT_FLAG_TELEPORT_PASSENGERS,
+            PlayerTeleportEvent.TeleportCause.COMMAND, null
+        );
+
+        return true;
+    }
+
+    @Override
+    public List<String> tabComplete(final CommandSender sender, final String alias,
+                                    final String[] args) throws IllegalArgumentException {
+        if (!(sender instanceof CraftPlayer playerSender)) {
+            return new ArrayList<>();
+        }
+
+        final List<ServerPlayer> players = MinecraftServer.getServer().getPlayerList().players;
+
+        // The laziest implementation possible.
+        final Function<ServerPlayer, String> playerToName = (final ServerPlayer value) -> {
+            return playerSender.getHandle().pendingTpas.contains(value.getUUID()) ? value.getGameProfile().getName() : null;
+        };
+
+        if (args.length == 0) {
+            return CommandUtil.getSortedList(players, playerToName);
+        } else if (args.length == 1) {
+            return CommandUtil.getSortedList(players, playerToName, args[0]);
+        }
+
+        return new ArrayList<>();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPADeny.java b/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPADeny.java
new file mode 100644
index 0000000000000000000000000000000000000000..5bf205d8c0a03ba932be85cc1a63d6cea304b517
--- /dev/null
+++ b/src/main/java/io/papermc/paper/threadedregions/commands/CommandsTPADeny.java
@@ -0,0 +1,99 @@
+package io.papermc.paper.threadedregions.commands;
+
+import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.format.NamedTextColor;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.craftbukkit.entity.CraftPlayer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+public final class CommandsTPADeny extends Command {
+
+    public CommandsTPADeny() {
+        super("tpadeny");
+        this.setUsage("/<command> <player name>");
+    }
+
+    @Override
+    public boolean testPermissionSilent(final CommandSender target) {
+        return true;
+    }
+
+    @Override
+    public boolean execute(final CommandSender sender, final String commandLabel, final String[] args) {
+        if (!(sender instanceof CraftPlayer playerSender)) {
+            sender.sendMessage(commandLabel + " only works for players");
+            return true;
+        }
+
+        if (args.length != 1) {
+            sender.sendMessage(Component.text("Usage: /" + commandLabel + " <player name>", NamedTextColor.DARK_RED));
+            return true;
+        }
+
+        final ServerPlayer target = CommandUtil.getPlayer(args[0]);
+
+        if (target == null) {
+            sender.sendMessage(
+                Component.text()
+                    .append(Component.text("Found no such player ", NamedTextColor.DARK_RED))
+                    .append(Component.text(args[0], NamedTextColor.RED))
+                    .build()
+            );
+            return true;
+        }
+
+        if (!playerSender.getHandle().pendingTpas.remove(target.getUUID())) {
+            sender.sendMessage(
+                Component.text()
+                    .append(Component.text("No tpa request to reject from ", NamedTextColor.DARK_RED))
+                    .append(Component.text(args[0], NamedTextColor.RED))
+                    .build()
+            );
+            return true;
+        }
+
+        sender.sendMessage(
+            Component.text()
+                .append(Component.text("Rejected tpa request from ", NamedTextColor.GRAY))
+                .append(Component.text(target.getGameProfile().getName(), NamedTextColor.GREEN))
+                .build()
+        );
+        target.getBukkitEntity().sendMessage(
+            Component.text()
+                .append(Component.text(playerSender.getName(), NamedTextColor.RED))
+                .append(Component.text(" rejected", NamedTextColor.DARK_RED))
+                .append(Component.text(" your tpa request!", NamedTextColor.GRAY))
+                .build()
+        );
+
+        return true;
+    }
+
+    @Override
+    public List<String> tabComplete(final CommandSender sender, final String alias,
+                                    final String[] args) throws IllegalArgumentException {
+        if (!(sender instanceof CraftPlayer playerSender)) {
+            return new ArrayList<>();
+        }
+
+        final List<ServerPlayer> players = MinecraftServer.getServer().getPlayerList().players;
+
+        // The laziest implementation possible.
+        final Function<ServerPlayer, String> playerToName = (final ServerPlayer value) -> {
+            return playerSender.getHandle().pendingTpas.contains(value.getUUID()) ? value.getGameProfile().getName() : null;
+        };
+
+        if (args.length == 0) {
+            return CommandUtil.getSortedList(players, playerToName);
+        } else if (args.length == 1) {
+            return CommandUtil.getSortedList(players, playerToName, args[0]);
+        }
+
+        return new ArrayList<>();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/util/CachedLists.java b/src/main/java/io/papermc/paper/util/CachedLists.java
index e08f4e39db4ee3fed62e37364d17dcc5c5683504..03d239460a2e856c1f59d6bcd95811c8e4e0cf6d 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.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+        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.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+        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.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+        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.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+        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.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+        if (worldData != null) {
+            worldData.resetCollisionLists();
+        }
+        // Folia end - region threading
     }
 }
diff --git a/src/main/java/io/papermc/paper/util/CoordinateUtils.java b/src/main/java/io/papermc/paper/util/CoordinateUtils.java
index 413e4b6da027876dbbe8eb78f2568a440f431547..d29a4a3bab456df99fbccddc832a9ac2da880f31 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.fastFloor(pos.x);
+    }
+
+    public static int getBlockY(final Vec3 pos) {
+        return Mth.fastFloor(pos.y);
+    }
+
+    public static int getBlockZ(final Vec3 pos) {
+        return Mth.fastFloor(pos.z);
+    }
+
+    public static int getChunkX(final Vec3 pos) {
+        return Mth.fastFloor(pos.x) >> 4;
+    }
+
+    public static int getChunkY(final Vec3 pos) {
+        return Mth.fastFloor(pos.y) >> 4;
+    }
+
+    public static int getChunkZ(final Vec3 pos) {
+        return Mth.fastFloor(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 6898c704e60d89d53c8ed114e5e12f73ed63605a..594ada3cdec25784c7bd6abb9ad42d3f1e2bd733 100644
--- a/src/main/java/io/papermc/paper/util/MCUtil.java
+++ b/src/main/java/io/papermc/paper/util/MCUtil.java
@@ -28,6 +28,7 @@ import net.minecraft.world.level.ClipContext;
 import net.minecraft.world.level.Level;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.phys.Vec3;
 import org.apache.commons.lang.exception.ExceptionUtils;
 import com.mojang.authlib.GameProfile;
 import org.bukkit.Location;
@@ -332,6 +333,7 @@ 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());
             }
@@ -472,6 +474,30 @@ 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 fc57850b80303fcade89ca95794f63910404a407..7de0bd89b13dcb550cf78ceda625f5ab9f9f3599 100644
--- a/src/main/java/io/papermc/paper/util/TickThread.java
+++ b/src/main/java/io/papermc/paper/util/TickThread.java
@@ -1,8 +1,19 @@
 package io.papermc.paper.util;
 
+import io.papermc.paper.threadedregions.RegionShutdownThread;
+import io.papermc.paper.threadedregions.RegionisedWorldData;
+import io.papermc.paper.threadedregions.ThreadedRegioniser;
+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;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.Mth;
 import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.phys.Vec3;
 import org.bukkit.Bukkit;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -38,6 +49,20 @@ public class TickThread extends Thread {
         }
     }
 
+    public static void ensureTickThread(final ServerLevel world, final BlockPos pos, final String reason) {
+        if (!isTickThreadFor(world, pos)) {
+            MinecraftServer.LOGGER.error("Thread " + Thread.currentThread().getName() + " failed main thread check: " + reason, new Throwable());
+            throw new IllegalStateException(reason);
+        }
+    }
+
+    public static void ensureTickThread(final ServerLevel world, final ChunkPos pos, final String reason) {
+        if (!isTickThreadFor(world, pos)) {
+            MinecraftServer.LOGGER.error("Thread " + Thread.currentThread().getName() + " failed main thread check: " + reason, new Throwable());
+            throw new IllegalStateException(reason);
+        }
+    }
+
     public static void ensureTickThread(final ServerLevel world, final int chunkX, final int chunkZ, final String reason) {
         if (!isTickThreadFor(world, chunkX, chunkZ)) {
             MinecraftServer.LOGGER.error("Thread " + Thread.currentThread().getName() + " failed main thread check: " + reason, new Throwable());
@@ -77,11 +102,75 @@ public class TickThread extends Thread {
         return Thread.currentThread() instanceof TickThread;
     }
 
+    public static boolean isShutdownThread() {
+        return Thread.currentThread().getClass() == RegionShutdownThread.class;
+    }
+
+    public static boolean isTickThreadFor(final ServerLevel world, final BlockPos pos) {
+        return isTickThreadFor(world, pos.getX() >> 4, pos.getZ() >> 4);
+    }
+
+    public static boolean isTickThreadFor(final ServerLevel world, final ChunkPos pos) {
+        return isTickThreadFor(world, pos.x, pos.z);
+    }
+
+    public static boolean isTickThreadFor(final ServerLevel world, final Vec3 pos) {
+        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 Thread.currentThread() instanceof TickThread;
+        final ThreadedRegioniser.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 int chunkX, final int chunkZ, final int radius) {
+        final ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            return isShutdownThread();
+        }
+
+        final int minSectionX = (chunkX - radius) >> world.regioniser.sectionChunkShift;
+        final int maxSectionX = (chunkX + radius) >> world.regioniser.sectionChunkShift;
+        final int minSectionZ = (chunkZ - radius) >> world.regioniser.sectionChunkShift;
+        final int maxSectionZ = (chunkZ + radius) >> world.regioniser.sectionChunkShift;
+
+        for (int secZ = minSectionZ; secZ <= maxSectionZ; ++secZ) {
+            for (int secX = minSectionX; secX <= maxSectionX; ++secX) {
+                final int lowerLeftCX = secX << world.regioniser.sectionChunkShift;
+                final int lowerLeftCZ = secZ << world.regioniser.sectionChunkShift;
+                if (world.regioniser.getRegionAtUnsynchronised(lowerLeftCX, lowerLeftCZ) != region) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
     }
 
     public static boolean isTickThreadFor(final Entity entity) {
-        return Thread.currentThread() instanceof TickThread;
+        if (entity == null) {
+            return true;
+        }
+        final ThreadedRegioniser.ThreadedRegion<TickRegions.TickRegionData, TickRegions.TickRegionSectionData> region =
+            TickRegionScheduler.getCurrentRegion();
+        if (region == null) {
+            return isShutdownThread();
+        }
+
+        final Level level = entity.level;
+        if (level != region.regioniser.world) {
+            // world mismatch
+            return false;
+        }
+
+        final RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+
+        // pass through the check if the entity is removed and we own its chunk
+        return worldData.hasEntity(entity) || (entity.isRemoved() && !(entity instanceof ServerPlayer) && 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 ae5dd08de75a7ed231295f306fd0974da3988249..0674c69e7180c482bcace9797af877e09263e88b 100644
--- a/src/main/java/net/minecraft/commands/CommandSourceStack.java
+++ b/src/main/java/net/minecraft/commands/CommandSourceStack.java
@@ -66,7 +66,7 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
 
     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, (commandcontext, flag, j) -> {
-        }, EntityAnchorArgument.Anchor.FEET, CommandSigningContext.ANONYMOUS, TaskChainer.immediate(server));
+        }, EntityAnchorArgument.Anchor.FEET, CommandSigningContext.ANONYMOUS, TaskChainer.immediate((Runnable run) -> { io.papermc.paper.threadedregions.RegionisedServer.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, @Nullable ResultConsumer<CommandSourceStack> consumer, 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 330f6c79417378da855326b4da665f9d240e748d..22f06033a731c3ba1b815842be7a9d575fa820f2 100644
--- a/src/main/java/net/minecraft/commands/Commands.java
+++ b/src/main/java/net/minecraft/commands/Commands.java
@@ -139,12 +139,12 @@ 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);
-        DataCommands.register(this.dispatcher);
-        DataPackCommand.register(this.dispatcher);
-        DebugCommand.register(this.dispatcher);
+        //CloneCommands.register(this.dispatcher, commandRegistryAccess); // Folia - region threading - TODO
+        //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);
@@ -154,44 +154,44 @@ 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);
-        ReloadCommand.register(this.dispatcher);
+        //ReloadCommand.register(this.dispatcher); // Folia - region threading
         RecipeCommand.register(this.dispatcher);
         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);
         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);
+        //WorldBorderCommand.register(this.dispatcher); // Folia - region threading - TODO later
         if (JvmProfiler.INSTANCE.isAvailable()) {
             JfrCommand.register(this.dispatcher);
         }
@@ -208,8 +208,8 @@ 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);
@@ -417,9 +417,12 @@ public class Commands {
         }
         // Paper start - Async command map building
         new com.destroystokyo.paper.event.brigadier.AsyncPlayerSendCommandsEvent<CommandSourceStack>(player.getBukkitEntity(), (RootCommandNode) rootcommandnode, false).callEvent(); // Paper
-        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 309ad5a1da6b3a297d5526cd9247359ac5f49406..5a85fcbcd2966af95683106d4f459653983a28e6 100644
--- a/src/main/java/net/minecraft/core/dispenser/AbstractProjectileDispenseBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/AbstractProjectileDispenseBehavior.java
@@ -33,7 +33,7 @@ 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 958134519befadc27a5b647caf64acf272ee2db4..a0712ad55c8e02a88ddf55bb0e70e05dc1ddbcdc 100644
--- a/src/main/java/net/minecraft/core/dispenser/BoatDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/BoatDispenseItemBehavior.java
@@ -58,7 +58,7 @@ public class BoatDispenseItemBehavior extends DefaultDispenseItemBehavior {
         CraftItemStack craftItem = CraftItemStack.asCraftMirror(itemstack1);
 
         BlockDispenseEvent event = new BlockDispenseEvent(block, 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/core/dispenser/DefaultDispenseItemBehavior.java b/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java
index 1e6ba6d9cceda1d4867b183c3dbc03d317ed287f..de8cf0f0d34708b960f1c81cb10d813a797df02b 100644
--- a/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/DefaultDispenseItemBehavior.java
@@ -74,7 +74,7 @@ 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 58fa7b99dc7a9745afe6faf31c1804e95ed27dbe..28a260dfe6ba9f7e9ff161562dcb87a6314af87c 100644
--- a/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
+++ b/src/main/java/net/minecraft/core/dispenser/DispenseItemBehavior.java
@@ -221,7 +221,7 @@ 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);
                 }
 
@@ -276,7 +276,7 @@ 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);
                 }
 
@@ -329,7 +329,7 @@ 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);
                     }
 
@@ -385,7 +385,7 @@ 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);
                 }
 
@@ -459,7 +459,7 @@ 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);
                 }
 
@@ -498,7 +498,7 @@ 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);
                 }
 
@@ -556,7 +556,7 @@ 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);
                 }
 
@@ -628,7 +628,7 @@ 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);
                     }
 
@@ -701,7 +701,7 @@ 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);
                         }
 
@@ -748,7 +748,7 @@ 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);
                 }
 
@@ -809,7 +809,7 @@ 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);
                 }
 
@@ -827,7 +827,8 @@ public interface DispenseItemBehavior {
                     }
                 }
 
-                worldserver.captureTreeGeneration = true;
+                io.papermc.paper.threadedregions.RegionisedWorldData 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)) {
@@ -836,13 +837,13 @@ public interface DispenseItemBehavior {
                     worldserver.levelEvent(1505, blockposition, 0);
                 }
                 // CraftBukkit start
-                worldserver.captureTreeGeneration = false;
-                if (worldserver.capturedBlockStates.size() > 0) {
+                worldData.captureTreeGeneration = false; // Folia - region threading
+                if (worldData.capturedBlockStates.size() > 0) { // Folia - region threading
                     TreeType treeType = SaplingBlock.treeType;
                     SaplingBlock.treeType = null;
                     Location location = new Location(worldserver.getWorld(), blockposition.getX(), blockposition.getY(), blockposition.getZ());
-                    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);
@@ -877,7 +878,7 @@ 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);
                 }
 
@@ -934,7 +935,7 @@ 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);
                 }
 
@@ -983,7 +984,7 @@ 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);
                 }
 
@@ -1056,7 +1057,7 @@ 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 d1127d93a85a837933d0d73c24cacac4adc3a5b9..ac9f4f2ac817e5fe9a15759c549a57ad8473b6ac 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 0159ed9cbc644c39fa79e62327f13375193fdc98..a930c8eb64d6c7044646d6b0156e202ea334a1f9 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()) { // Folia - region threading
                 pointer.getLevel().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 38c09c65dfa4a7a0c80d36f726c1fd028cbe05f8..5e74408bbdcc9b434447e3d9cf7523ef122ec03e 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -73,7 +73,7 @@ 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<Connection.PacketHolder> queue = Queues.newConcurrentLinkedQueue();
+    private final Queue<Connection.PacketHolder> queue = new ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<>();
     public Channel channel;
     public SocketAddress address;
     // Spigot Start
@@ -81,7 +81,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     public com.mojang.authlib.properties.Property[] spoofedProfile;
     public boolean preparing = true;
     // Spigot End
-    private PacketListener packetListener;
+    private volatile PacketListener packetListener; // Folia - region threading
     private Component disconnectedReason;
     private boolean encrypted;
     private boolean disconnectionHandled;
@@ -177,6 +177,32 @@ 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.ServerGamePacketListenerImpl;
+    }
+    // Folia end - region threading
+
     public void channelActive(ChannelHandlerContext channelhandlercontext) throws Exception {
         super.channelActive(channelhandlercontext);
         this.channel = channelhandlercontext.channel();
@@ -191,6 +217,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             Connection.LOGGER.error(LogUtils.FATAL_MARKER, "Failed to change protocol to handshake", throwable);
         }
 
+        this.becomeActive = true; // Folia - region threading
     }
 
     public void setProtocol(ConnectionProtocol state) {
@@ -372,13 +399,6 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             return; // Do nothing
         }
         packet.onPacketDispatch(getPlayer());
-        if (connected && (InnerUtil.canSendImmediate(this, packet) || (
-            io.papermc.paper.util.MCUtil.isMainThread() && packet.isReady() && this.queue.isEmpty() &&
-            (packet.getExtraPackets() == null || packet.getExtraPackets().isEmpty())
-        ))) {
-            this.sendPacket(packet, callbacks, null); // Paper
-            return;
-        }
         // write the packets to the queue, then flush - antixray hooks there already
         java.util.List<Packet> extraPackets = InnerUtil.buildExtraPackets(packet);
         boolean hasExtraPackets = extraPackets != null && !extraPackets.isEmpty();
@@ -496,66 +516,58 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
 
     // Paper start - rewrite this to be safer if ran off main thread
     private boolean flushQueue() { // void -> boolean
-        if (!isConnected()) {
+        if (!this.isConnected()) {
             return true;
         }
-        if (io.papermc.paper.util.MCUtil.isMainThread()) {
-            return processQueue();
-        } else if (isPending) {
-            // Should only happen during login/status stages
-            synchronized (this.queue) {
-                return this.processQueue();
-            }
-        }
-        return false;
+        return this.processQueue();
+    }
+
+    // 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 boolean canWritePackets() {
+        PacketHolder holder = this.queue.peek();
+        return holder != null && holder.packet.isReady();
     }
+
     private boolean processQueue() {
-        try { // Paper - add pending task queue
-        if (this.queue.isEmpty()) return true;
-        // Paper start - make only one flush call per sendPacketQueue() call
         final boolean needsFlush = this.canFlush;
-        boolean hasWrotePacket = false;
-        // Paper end - make only one flush call per sendPacketQueue() call
-        // 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
-        java.util.Iterator<PacketHolder> iterator = this.queue.iterator();
-        while (iterator.hasNext()) {
-            PacketHolder queued = iterator.next(); // poll -> peek
-
-            // Fix NPE (Spigot bug caused by handleDisconnection())
-            if (false && queued == null) { // Paper - diff on change, this logic is redundant: iterator guarantees ret of an element - on change, hook the flush logic here
-                return true;
-            }
+        while (this.canWritePackets()) {
+            final boolean set = this.flushingQueue.getAndSet(true);
+            try {
+                if (set) {
+                    // we didn't acquire the lock, break
+                    return false;
+                }
 
-            // Paper start - checking isConsumed flag and skipping packet sending
-            if (queued.isConsumed()) {
-                continue;
-            }
-            // Paper end - checking isConsumed flag and skipping packet sending
+                boolean justFlushed = true;
 
-            Packet<?> packet = queued.packet;
-            if (!packet.isReady()) {
-                // Paper start - make only one flush call per sendPacketQueue() call
-                if (hasWrotePacket && (needsFlush || this.canFlush)) {
+                PacketHolder holder;
+                for (;;) {
+                    // synchronise so that queue clears appear atomic
+                    synchronized (this.queue) {
+                        holder = ((ca.spottedleaf.concurrentutil.collection.MultiThreadedQueue<PacketHolder>)this.queue).pollIf((PacketHolder h) -> {
+                            return h.packet.isReady();
+                        });
+                    }
+                    if (holder == null) {
+                        break;
+                    }
+                    justFlushed = (!this.canWritePackets() && (needsFlush || this.canFlush));
+                    this.sendPacket(holder.packet, holder.listener, justFlushed ? Boolean.TRUE : Boolean.FALSE); // Paper - make only one flush call per sendPacketQueue() call
+                }
+
+                if (!justFlushed) {
                     this.flush();
                 }
-                // Paper end - make only one flush call per sendPacketQueue() call
-                return false;
-            } else {
-                iterator.remove();
-                if (queued.tryMarkConsumed()) { // Paper - try to mark isConsumed flag for de-duplicating packet
-                    this.sendPacket(packet, queued.listener, (!iterator.hasNext() && (needsFlush || this.canFlush)) ? Boolean.TRUE : Boolean.FALSE); // Paper - make only one flush call per sendPacketQueue() call
-                    hasWrotePacket = true; // Paper - make only one flush call per sendPacketQueue() call
+            } finally {
+                if (!set) {
+                    this.flushingQueue.set(false);
                 }
             }
         }
         return true;
-        } finally { // Paper start - add pending task queue
-            Runnable r;
-            while ((r = this.pendingTasks.poll()) != null) {
-                this.channel.eventLoop().execute(r);
-            }
-        } // Paper end - add pending task queue
     }
     // Paper end
 
@@ -564,21 +576,41 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     private static int currTick; // Paper
     public void tick() {
         this.flushQueue();
-        // Paper start
-        if (Connection.currTick != net.minecraft.server.MinecraftServer.currentTick) {
-            Connection.currTick = net.minecraft.server.MinecraftServer.currentTick;
-            Connection.joinAttemptsThisTick = 0;
+        // 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.ServerGamePacketListenerImpl gamePacketListener) {
+                gamePacketListener.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
+        if (!this.isConnected()) {
+            // disconnected from above
+            this.handleDisconnection();
+            return;
+        }
+        // Folia end - region threading
+        // Folia - this is broken
         PacketListener packetlistener = this.packetListener;
 
         if (packetlistener instanceof TickablePacketListener) {
             TickablePacketListener tickablepacketlistener = (TickablePacketListener) packetlistener;
 
             // Paper start - limit the number of joins which can be processed each tick
-            if (!(this.packetListener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl loginPacketListener)
-                || loginPacketListener.state != net.minecraft.server.network.ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT
-                || 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
@@ -618,13 +650,21 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     // Paper start
     public void clearPacketQueue() {
         net.minecraft.server.level.ServerPlayer player = getPlayer();
-        queue.forEach(queuedPacket -> {
+        java.util.List<Connection.PacketHolder> queuedPackets = new java.util.ArrayList<>();
+        // synchronise so that flushQueue does not poll values while the queue is being cleared
+        synchronized (this.queue) {
+            Connection.PacketHolder packetHolder;
+            while ((packetHolder = this.queue.poll()) != null) {
+                queuedPackets.add(packetHolder);
+            }
+        }
+
+        for (Connection.PacketHolder queuedPacket : queuedPackets) {
             Packet<?> packet = queuedPacket.packet;
             if (packet.hasFinishListener()) {
                 packet.onPacketDispatchFinish(player, null);
             }
-        });
-        queue.clear();
+        }
     }
     // Paper end
     public void disconnect(Component disconnectReason) {
@@ -636,6 +676,7 @@ 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
 
     }
 
@@ -784,13 +825,27 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
                     final net.minecraft.server.network.ServerGamePacketListenerImpl playerConnection = (net.minecraft.server.network.ServerGamePacketListenerImpl) packetListener;
                     new com.destroystokyo.paper.event.player.PlayerConnectionCloseEvent(playerConnection.player.getUUID(),
                         playerConnection.player.getScoreboardName(), ((java.net.InetSocketAddress)address).getAddress(), false).callEvent();
+                    // Note: It can be in the connection set if it is in ready to accept if handleAcceptedLogin fails
+                    // Folia start - region threading
+                    net.minecraft.server.MinecraftServer.getServer().getPlayerList().removeConnection(
+                        playerConnection.player.getScoreboardName(),
+                        playerConnection.player.getUUID(), this
+                    );
+                    // Folia end - region threading
                 } else if (packetListener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl) {
                     /* Player is login stage */
                     final net.minecraft.server.network.ServerLoginPacketListenerImpl loginListener = (net.minecraft.server.network.ServerLoginPacketListenerImpl) packetListener;
-                    switch (loginListener.state) {
-                        case READY_TO_ACCEPT:
-                        case DELAY_ACCEPT:
-                        case ACCEPTED:
+                    // Folia start - region threading
+                    if (loginListener.state.ordinal() >= net.minecraft.server.network.ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT.ordinal()) {
+                        // Note: It can be in the connection set if it is in ready to accept if handleAcceptedLogin fails
+                        net.minecraft.server.MinecraftServer.getServer().getPlayerList().removeConnection(
+                            loginListener.gameProfile.getName(),
+                            net.minecraft.core.UUIDUtil.getOrCreatePlayerUUID(loginListener.gameProfile),
+                            this
+                        );
+                    }
+                    // Folia end - region threading
+                    if (loginListener.state.ordinal() >= net.minecraft.server.network.ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT.ordinal()) { // Folia - region threading - rewrite login process
                             final com.mojang.authlib.GameProfile profile = loginListener.gameProfile; /* Should be non-null at this stage */
                             new com.destroystokyo.paper.event.player.PlayerConnectionCloseEvent(profile.getId(), profile.getName(),
                                 ((java.net.InetSocketAddress)address).getAddress(), false).callEvent();
diff --git a/src/main/java/net/minecraft/network/protocol/PacketUtils.java b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
index 27d4aa45e585842c04491839826d405d6f447f0e..e6ef0691588fbb33d47692db4269c56557814c9b 100644
--- a/src/main/java/net/minecraft/network/protocol/PacketUtils.java
+++ b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
@@ -2,6 +2,7 @@ package net.minecraft.network.protocol;
 
 import com.mojang.logging.LogUtils;
 import net.minecraft.network.PacketListener;
+import net.minecraft.server.level.ServerPlayer;
 import org.slf4j.Logger;
 
 // CraftBukkit start
@@ -41,7 +42,7 @@ public class PacketUtils {
 
     public static <T extends PacketListener> void ensureRunningOnSameThread(Packet<T> packet, T listener, BlockableEventLoop<?> engine) throws RunningOnDifferentThreadException {
         if (!engine.isSameThread()) {
-            engine.execute(() -> { // Paper - Fix preemptive player kick on a server shutdown.
+            Runnable run = () -> { // Folia - region threading
                 packetProcessing.push(listener); // Paper - detailed watchdog information
                 try { // Paper - detailed watchdog information
                 if (MinecraftServer.getServer().hasStopped() || (listener instanceof ServerGamePacketListenerImpl && ((ServerGamePacketListenerImpl) listener).processedDisconnect)) return; // CraftBukkit, MC-142590
@@ -71,7 +72,17 @@ public class PacketUtils {
                 }
                 // Paper end - detailed watchdog information
 
-            });
+            }; // Folia start - region threading
+            ServerGamePacketListenerImpl actualListener = (ServerGamePacketListenerImpl)listener;
+            // ignore retired state, if removed then we don't want the packet to be handled
+            actualListener.player.getBukkitEntity().taskScheduler.schedule(
+                (ServerPlayer player) -> {
+                    run.run();
+                },
+                null,
+                1L
+            );
+            // Folia end - region threading
             throw RunningOnDifferentThreadException.RUNNING_ON_DIFFERENT_THREAD;
             // CraftBukkit start - SPIGOT-5477, MC-142590
         } else if (MinecraftServer.getServer().hasStopped() || (listener instanceof ServerGamePacketListenerImpl && ((ServerGamePacketListenerImpl) listener).processedDisconnect)) {
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 2ee4e5e8d17a3a1e6a342c74b13135df030ffef6..9577b633ecf5ebd1ff5bf79aa6ea61160f59e764 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -291,7 +291,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public org.bukkit.command.ConsoleCommandSender console;
     public org.bukkit.command.RemoteConsoleCommandSender remoteConsole;
     //public ConsoleReader reader; // Paper
-    public static int currentTick = 0; // Paper - Further improve tick loop
+    //public static int currentTick = 0; // Paper - Further improve tick loop // Folia - region threading
     public java.util.Queue<Runnable> processQueue = new java.util.concurrent.ConcurrentLinkedQueue<Runnable>();
     public int autosavePeriod;
     public Commands vanillaCommandDispatcher;
@@ -304,12 +304,40 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     public final double[] recentTps = new double[ 3 ];
     // Spigot end
     public final io.papermc.paper.configuration.PaperConfigurations paperConfigurations;
-    public static long currentTickLong = 0L; // Paper
+    //public static long currentTickLong = 0L; // Paper // Folia - threaded regions
 
     public volatile Thread shutdownThread; // Paper
     public volatile boolean abnormalExit = false; // Paper
     public boolean isIteratingOverLevels = false; // Paper
 
+    // Folia start - regionised ticking
+    public final io.papermc.paper.threadedregions.RegionisedServer regionisedServer = new io.papermc.paper.threadedregions.RegionisedServer();
+
+    @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
@@ -602,7 +630,21 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
             worlddata.setModdedInfo(this.getServerModName(), this.getModdedStatus().shouldReportAsModified());
             this.addLevel(world); // Paper - move up
-            this.initWorld(world, worlddata, 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 - move up
             this.getPlayerList().addWorldborderListener(world);
@@ -614,6 +656,7 @@ 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.RegionisedServer.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()));
         }
@@ -681,7 +724,7 @@ 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());
@@ -702,6 +745,7 @@ 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);
             }
 
@@ -783,7 +827,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end
 
         // this.nextTickTime = SystemUtils.getMillis() + 10L;
-        this.executeModerately();
+        //this.executeModerately(); // Folia - region threading
         // Iterator iterator = this.levels.values().iterator();
         }
 
@@ -806,7 +850,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
         // CraftBukkit start
         // this.nextTickTime = SystemUtils.getMillis() + 10L;
-        this.executeModerately();
+        //this.executeModerately(); // Folia - region threading
         // CraftBukkit end
         if (worldserver.getWorld().getKeepSpawnInMemory()) worldloadlistener.stop(); // Paper
         chunkproviderserver.getLightEngine().setTaskPerBatch(worldserver.paperConfig().misc.lightQueueSize); // Paper - increase light queue size
@@ -911,7 +955,37 @@ 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;
@@ -921,7 +995,7 @@ 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();
@@ -957,6 +1031,13 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             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();
 
@@ -972,6 +1053,11 @@ 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 {
@@ -1025,6 +1111,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         if (isDebugging()) io.papermc.paper.util.TraceUtil.dumpTraceForThread("Server stopped"); // Paper
         // Paper end
         this.running = false;
+        this.stopServer(); // Folia - region threading
         if (waitForShutdown) {
             try {
                 this.serverThread.join();
@@ -1108,6 +1195,19 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             this.status.setEnforcesSecureChat(this.enforceSecureProfile());
             this.updateStatusIcon(this.status);
 
+            // Folia start - region threading
+            if (true) {
+                io.papermc.paper.threadedregions.RegionisedServer.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");
@@ -1143,8 +1243,8 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                     this.lastOverloadWarning = this.nextTickTime;
                 }
 
-                ++MinecraftServer.currentTickLong; // Paper
-                if ( ++MinecraftServer.currentTick % MinecraftServer.SAMPLE_INTERVAL == 0 )
+                //++MinecraftServer.currentTickLong; // Paper // Folia - threaded regions
+                if ( false ) // Folia - region threading
                 {
                     final long diff = curTime - tickSection;
                     java.math.BigDecimal currentTps = TPS_BASE.divide(new java.math.BigDecimal(diff), 30, java.math.RoundingMode.HALF_UP);
@@ -1170,7 +1270,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
                 this.nextTickTime += 50L;
                 this.startMetricsRecordingTick();
                 this.profiler.push("tick");
-                this.tickServer(this::haveTime);
+                this.tickServer(curTime, this.nextTickTime, 0L, null); // Folia - region threading
                 this.profiler.popPush("nextTickWait");
                 this.mayHaveDelayedTasks = true;
                 this.delayedTasksMaxNextTickTime = Math.max(Util.getMillis() + 50L, this.nextTickTime);
@@ -1308,6 +1408,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     @Override
     public boolean pollTask() {
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         boolean flag = this.pollTaskInternal();
 
         this.mayHaveDelayedTasks = flag;
@@ -1315,6 +1416,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
     }
 
     private boolean pollTaskInternal() {
+        if (true) throw new UnsupportedOperationException(); // Folia - region threading
         if (super.pollTask()) {
             this.executeMidTickTasks(); // Paper - execute chunk tasks mid tick
             return true;
@@ -1337,6 +1439,7 @@ 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);
     }
@@ -1380,22 +1483,61 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
     public void onServerExit() {}
 
-    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)) {
+                        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);
+                    } // 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
+        // Folia - region threading - move up
+
+        // Folia start - region threading
+        if (region != null) {
+            region.getTaskQueueData().drainTasks();
+            // 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();
+                }
+            }
+            // now tick connections
+            region.world.getCurrentWorldData().tickConnections(); // Folia - region threading
+        }
+        // Folia end - region threading
 
         ++this.tickCount;
-        this.tickChildren(shouldKeepTicking);
-        if (i - this.lastServerStatus >= 5000000000L) {
+        this.tickChildren(shouldKeepTicking, region); // Folia - region threading
+        if (region == null && i - this.lastServerStatus >= 5000000000L) { // Folia - region threading - moved to global tick
             this.lastServerStatus = i;
             this.status.setPlayers(new ServerStatus.Players(this.getMaxPlayers(), this.getPlayerCount()));
             if (!this.hidesOnlinePlayers()) {
@@ -1429,9 +1571,9 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
             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 {
@@ -1441,16 +1583,17 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end
         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
         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(this.tickCount, ((double)(endTime - startTime) / 1000000D), remaining).callEvent(); // Folia - region ticking
         // Paper end
         this.profiler.push("tallying");
+        if (region == null) { // Folia - region threading
         long l = this.tickTimes[this.tickCount % 100] = Util.getNanos() - i;
 
         this.averageTickTime = this.averageTickTime * 0.8F + (float) l / 1000000.0F * 0.19999999F;
@@ -1463,18 +1606,19 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end
 
         this.frameTimer.logFrameDuration(i1 - i);
+        } // Folia - region threading
         this.profiler.pop();
         org.spigotmc.WatchdogThread.tick(); // Spigot
         co.aikar.timings.TimingsManager.FULL_SERVER_TICK.stopTiming(); // Paper
     }
 
-    public void tickChildren(BooleanSupplier shouldKeepTicking) {
+    public void tickChildren(BooleanSupplier shouldKeepTicking, io.papermc.paper.threadedregions.TickRegions.TickRegionData region) { // Folia - region threading
         MinecraftTimings.bukkitSchedulerTimer.startTiming(); // Spigot // Paper
-        this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // CraftBukkit
+        if (region == null) this.server.getScheduler().mainThreadHeartbeat(this.tickCount); // CraftBukkit // Folia - region threading - TODO REPLACE CRAFT SCHEDULER
         MinecraftTimings.bukkitSchedulerTimer.stopTiming(); // Spigot // Paper
         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 - moved down
@@ -1482,7 +1626,7 @@ 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
@@ -1490,13 +1634,13 @@ 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 - optimize time updates
-        for (final ServerLevel world : this.getAllLevels()) {
+       for (final ServerLevel world : (region == null ? this.getAllLevels() : Arrays.asList(region.world))) { // Folia - region threading
             final boolean doDaylight = world.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT);
             final long dayTime = world.getDayTime();
             long worldTime = world.getGameTime();
             final ClientboundSetTimePacket worldPacket = new ClientboundSetTimePacket(worldTime, dayTime, doDaylight);
-            for (Player entityhuman : world.players()) {
-                if (!(entityhuman instanceof ServerPlayer) || (tickCount + entityhuman.getId()) % 20 != 0) {
+            for (Player entityhuman : world.getLocalPlayers()) { // Folia - region threading
+                if (!(entityhuman instanceof ServerPlayer) || ((region == null ? tickCount : region.getCurrentTick()) + entityhuman.getId()) % 20 != 0) { // Folia - region threading
                     continue;
                 }
                 ServerPlayer entityplayer = (ServerPlayer) entityhuman;
@@ -1509,13 +1653,11 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         // Paper end
         MinecraftTimings.timeUpdateTimer.stopTiming(); // Spigot // Paper
 
-        this.isIteratingOverLevels = true; // Paper
-        Iterator iterator = this.getAllLevels().iterator(); // Paper - move down
+        if (region == null) this.isIteratingOverLevels = true; // Paper // Folia - region threading
+        Iterator iterator = region == null ? this.getAllLevels().iterator() : Arrays.asList(region.world).iterator(); // Paper - 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
-            worldserver.hasEntityMoveEvent =  io.papermc.paper.event.entity.EntityMoveEvent.getHandlerList().getRegisteredListeners().length > 0; // Paper
-            net.minecraft.world.level.block.entity.HopperBlockEntity.skipHopperEvents = worldserver.paperConfig().hopper.disableMoveEvent || org.bukkit.event.inventory.InventoryMoveItemEvent.getHandlerList().getRegisteredListeners().length == 0; // Paper
+            // Folia - region threading
 
             this.profiler.push(() -> {
                 return worldserver + " " + worldserver.dimension().location();
@@ -1532,7 +1674,7 @@ 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();
@@ -1556,17 +1698,17 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
 
             this.profiler.pop();
             this.profiler.pop();
-            worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions
+            //worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions // Folia - region threading
         }
-        this.isIteratingOverLevels = false; // Paper
+        if (region == null) this.isIteratingOverLevels = false; // Paper // Folia - region threading
 
         this.profiler.popPush("connection");
         MinecraftTimings.connectionTimer.startTiming(); // Spigot
-        this.getConnection().tick();
+        if (region == null) this.getConnection().tick(); // Folia - region threading - moved into post entity scheduler tick
         MinecraftTimings.connectionTimer.stopTiming(); // Spigot
         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) {
             GameTestTicker.SINGLETON.tick();
@@ -1575,7 +1717,7 @@ 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
@@ -1948,6 +2090,15 @@ 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.RegionisedServer.getInstance().addTaskWithoutNotify(() -> {
+                io.papermc.paper.threadedregions.RegionisedServer.getInstance().invalidateStatus();
+            });
+            return;
+        }
+        // Folia end - region threading
         this.lastServerStatus = 0L;
     }
 
@@ -1962,6 +2113,7 @@ 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 RejectedExecutionException("Server already shutting down");
         } else {
@@ -2710,33 +2862,18 @@ 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;
+    private boolean tickMidTickTasks(io.papermc.paper.threadedregions.RegionisedWorldData worldData) { // Folia - region threading
+        // Folia - region threading - only execute for one world
+        return worldData.world.getChunkSource().pollTask();
     }
 
     public final void executeMidTickTasks() {
         org.spigotmc.AsyncCatcher.catchOp("mid tick chunk task execution");
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData(); // 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;
@@ -2745,13 +2882,13 @@ 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
@@ -2764,7 +2901,7 @@ 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;
                 }
             }
diff --git a/src/main/java/net/minecraft/server/commands/AdvancementCommands.java b/src/main/java/net/minecraft/server/commands/AdvancementCommands.java
index 147c256e794f3e579e70927329fd1905ad1b33af..10f3c46334c77241f3cb6bbd833b381d7e68d527 100644
--- a/src/main/java/net/minecraft/server/commands/AdvancementCommands.java
+++ b/src/main/java/net/minecraft/server/commands/AdvancementCommands.java
@@ -61,7 +61,11 @@ public class AdvancementCommands {
         int i = 0;
 
         for(ServerPlayer serverPlayer : targets) {
-            i += operation.perform(serverPlayer, selection);
+            i += 1; // Folia - region threading
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
+            operation.perform(serverPlayer, selection);
+            }, null, 1L); // Folia - region threading
+
         }
 
         if (i == 0) {
@@ -99,9 +103,13 @@ public class AdvancementCommands {
             throw new CommandRuntimeException(Component.translatable("commands.advancement.criterionNotFound", advancement.getChatComponent(), criterion));
         } else {
             for(ServerPlayer serverPlayer : targets) {
+                ++i; // Folia - region threading
+                serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
                 if (operation.performCriterion(serverPlayer, advancement, criterion)) {
-                    ++i;
+                    // Folia - region threading
                 }
+                }, null, 1L); // Folia - 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 e846bd5db018f79c083d29f8f7b305a3d7ab45f5..b01aeb7bae3b6d3d291f76d19e8807980452646c 100644
--- a/src/main/java/net/minecraft/server/commands/AttributeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/AttributeCommand.java
@@ -92,58 +92,113 @@ 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);
-        double d = livingEntity.getAttributeValue(attribute);
-        source.sendSuccess(Component.translatable("commands.attribute.value.get.success", getAttributeDescription(attribute), target.getName(), d), false);
-        return (int)(d * multiplier);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+            try {
+                LivingEntity livingEntity = getEntityWithAttribute(nmsEntity, attribute); // Folia - region threading
+                double d = livingEntity.getAttributeValue(attribute);
+                source.sendSuccess(Component.translatable("commands.attribute.value.get.success", getAttributeDescription(attribute), nmsEntity.getName(), d), false);
+            } 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);
-        double d = livingEntity.getAttributeBaseValue(attribute);
-        source.sendSuccess(Component.translatable("commands.attribute.base_value.get.success", getAttributeDescription(attribute), target.getName(), d), false);
-        return (int)(d * multiplier);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+            try {
+                LivingEntity livingEntity = getEntityWithAttribute(nmsEntity, attribute);
+                double d = livingEntity.getAttributeBaseValue(attribute);
+                source.sendSuccess(Component.translatable("commands.attribute.base_value.get.success", getAttributeDescription(attribute), nmsEntity.getName(), d), false);
+            } 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);
-        AttributeMap attributeMap = livingEntity.getAttributes();
-        if (!attributeMap.hasModifier(attribute, uuid)) {
-            throw ERROR_NO_SUCH_MODIFIER.create(target.getName(), getAttributeDescription(attribute), uuid);
-        } else {
-            double d = attributeMap.getModifierValue(attribute, uuid);
-            source.sendSuccess(Component.translatable("commands.attribute.modifier.value.get.success", uuid, getAttributeDescription(attribute), target.getName(), d), false);
-            return (int)(d * multiplier);
-        }
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+            try {
+                LivingEntity livingEntity = getEntityWithAttribute(nmsEntity, attribute);
+                AttributeMap attributeMap = livingEntity.getAttributes();
+                if (!attributeMap.hasModifier(attribute, uuid)) {
+                    throw ERROR_NO_SUCH_MODIFIER.create(nmsEntity.getName(), getAttributeDescription(attribute), uuid);
+                } else {
+                    double d = attributeMap.getModifierValue(attribute, uuid);
+                    source.sendSuccess(Component.translatable("commands.attribute.modifier.value.get.success", uuid, getAttributeDescription(attribute), nmsEntity.getName(), d), false);
+                }
+            } 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);
-        source.sendSuccess(Component.translatable("commands.attribute.base_value.set.success", getAttributeDescription(attribute), target.getName(), value), false);
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+            try {
+                getAttributeInstance(nmsEntity, attribute).setBaseValue(value);
+                source.sendSuccess(Component.translatable("commands.attribute.base_value.set.success", getAttributeDescription(attribute), nmsEntity.getName(), value), false);
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        // Folia end - region threading
         return 1;
     }
 
     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);
-        AttributeModifier attributeModifier = new AttributeModifier(uuid, name, value, operation);
-        if (attributeInstance.hasModifier(attributeModifier)) {
-            throw ERROR_MODIFIER_ALREADY_PRESENT.create(target.getName(), getAttributeDescription(attribute), uuid);
-        } else {
-            attributeInstance.addPermanentModifier(attributeModifier);
-            source.sendSuccess(Component.translatable("commands.attribute.modifier.add.success", uuid, getAttributeDescription(attribute), target.getName()), false);
-            return 1;
-        }
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+            try {
+                AttributeInstance attributeInstance = getAttributeInstance(nmsEntity, attribute);
+                AttributeModifier attributeModifier = new AttributeModifier(uuid, name, value, operation);
+                if (attributeInstance.hasModifier(attributeModifier)) {
+                    throw ERROR_MODIFIER_ALREADY_PRESENT.create(nmsEntity.getName(), getAttributeDescription(attribute), uuid);
+                } else {
+                    attributeInstance.addPermanentModifier(attributeModifier);
+                    source.sendSuccess(Component.translatable("commands.attribute.modifier.add.success", uuid, getAttributeDescription(attribute), nmsEntity.getName()), false);
+                }
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 1;
+        // Folia end - region threading
     }
 
     private static int removeModifier(CommandSourceStack source, Entity target, Holder<Attribute> attribute, UUID uuid) throws CommandSyntaxException {
-        AttributeInstance attributeInstance = getAttributeInstance(target, attribute);
-        if (attributeInstance.removePermanentModifier(uuid)) {
-            source.sendSuccess(Component.translatable("commands.attribute.modifier.remove.success", uuid, getAttributeDescription(attribute), target.getName()), false);
-            return 1;
-        } else {
-            throw ERROR_NO_SUCH_MODIFIER.create(target.getName(), getAttributeDescription(attribute), uuid);
-        }
+        // Folia start - region threading
+        target.getBukkitEntity().taskScheduler.schedule((LivingEntity nmsEntity) -> {
+            try {
+                AttributeInstance attributeInstance = getAttributeInstance(nmsEntity, attribute);
+                if (attributeInstance.removePermanentModifier(uuid)) {
+                    source.sendSuccess(Component.translatable("commands.attribute.modifier.remove.success", uuid, getAttributeDescription(attribute), nmsEntity.getName()), false);
+                } else {
+                    throw ERROR_NO_SUCH_MODIFIER.create(nmsEntity.getName(), getAttributeDescription(attribute), uuid);
+                }
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        }, null, 1L);
+        return 1;
+        // 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 74623df731de543d3ef5832e818b10adec7b0f01..74a5e35c66e4d6aeae61733ad3ef1e51c0cfd593 100644
--- a/src/main/java/net/minecraft/server/commands/ClearInventoryCommands.java
+++ b/src/main/java/net/minecraft/server/commands/ClearInventoryCommands.java
@@ -46,9 +46,12 @@ public class ClearInventoryCommands {
         int i = 0;
 
         for(ServerPlayer serverPlayer : targets) {
-            i += serverPlayer.getInventory().clearOrCountMatchingItems(item, maxCount, serverPlayer.inventoryMenu.getCraftSlots());
+            ++i;
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
+            serverPlayer.getInventory().clearOrCountMatchingItems(item, maxCount, serverPlayer.inventoryMenu.getCraftSlots());
             serverPlayer.containerMenu.broadcastChanges();
             serverPlayer.inventoryMenu.slotsChanged(serverPlayer.getInventory());
+            }, null, 1L); // Folia - region threading
         }
 
         if (i == 0) {
diff --git a/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java b/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
index 1bf4c5b36f53ef1e71d50d1a9af8e1410e5dff60..fd455c794fa52b565a5741b376bc394ac8dda07c 100644
--- a/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
+++ b/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
@@ -25,12 +25,14 @@ public class DefaultGameModeCommands {
         GameType gameType = minecraftServer.getForcedGameType();
         if (gameType != null) {
             for(ServerPlayer serverPlayer : minecraftServer.getPlayerList().getPlayers()) {
+                serverPlayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
                 // Paper start - extend PlayerGameModeChangeEvent
                 org.bukkit.event.player.PlayerGameModeChangeEvent event = serverPlayer.setGameMode(gameType, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.DEFAULT_GAMEMODE, net.kyori.adventure.text.Component.empty());
                 if (event != null && event.isCancelled()) {
                     source.sendSuccess(io.papermc.paper.adventure.PaperAdventure.asVanilla(event.cancelMessage()), false);
                 }
                 // Paper end
+                }, 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 bed3ffb18398f34077503ba2d7aa6ecc7c0537c2..8651d87632a4f5d0ccd69332a78f9a9969eb638f 100644
--- a/src/main/java/net/minecraft/server/commands/EffectCommands.java
+++ b/src/main/java/net/minecraft/server/commands/EffectCommands.java
@@ -76,7 +76,15 @@ 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;
                 }
             }
@@ -102,8 +110,16 @@ 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
             }
         }
 
@@ -128,8 +144,16 @@ 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 e639c0ec642910e66b1d68ae0b9208ef58d91fce..9ad71bda2f7498ad6e0853a1070c5be2d8016548 100644
--- a/src/main/java/net/minecraft/server/commands/EnchantCommand.java
+++ b/src/main/java/net/minecraft/server/commands/EnchantCommand.java
@@ -46,6 +46,12 @@ 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()) {
@@ -55,18 +61,26 @@ public class EnchantCommand {
 
             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);
+                                } 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 (CommandSyntaxException ex) {
+                            sendMessage(source, ex);
                         }
-                    } else if (targets.size() == 1) {
-                        throw ERROR_NO_ITEM.create(livingEntity.getName().getString());
-                    }
+                    }, null, 1L);
+                    ++i;
+                    // Folia end - region threading
                 } else if (targets.size() == 1) {
                     throw ERROR_NOT_LIVING_ENTITY.create(entity.getName().getString());
                 }
diff --git a/src/main/java/net/minecraft/server/commands/ExperienceCommand.java b/src/main/java/net/minecraft/server/commands/ExperienceCommand.java
index a628e3730b1c26c2e6a85c449440af0afe4c0d8d..6651376603c3fb2331ae0955343285ac7c37726f 100644
--- a/src/main/java/net/minecraft/server/commands/ExperienceCommand.java
+++ b/src/main/java/net/minecraft/server/commands/ExperienceCommand.java
@@ -46,14 +46,18 @@ public class ExperienceCommand {
     }
 
     private static int queryExperience(CommandSourceStack source, ServerPlayer player, ExperienceCommand.Type component) {
+        player.getBukkitEntity().taskScheduler.schedule((ServerPlayer p) -> { // Folia - region threading
         int i = component.query.applyAsInt(player);
         source.sendSuccess(Component.translatable("commands.experience.query." + component.name, player.getDisplayName(), i), false);
-        return i;
+        }, null, 1L); // Folia - region threading
+        return 0;
     }
 
     private static int addExperience(CommandSourceStack source, Collection<? extends ServerPlayer> targets, int amount, ExperienceCommand.Type component) {
         for(ServerPlayer serverPlayer : targets) {
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
             component.add.accept(serverPlayer, amount);
+            }, null, 1L); // Folia - region threading
         }
 
         if (targets.size() == 1) {
@@ -69,9 +73,12 @@ public class ExperienceCommand {
         int i = 0;
 
         for(ServerPlayer serverPlayer : targets) {
+            ++i; // Folia - region threading
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
             if (component.set.test(serverPlayer, amount)) {
-                ++i;
+                // 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 6c29947dc9259f453782de3c973c1cabb87e3de5..c8e60578f15a358223ed056460d3ea2c57b0cd40 100644
--- a/src/main/java/net/minecraft/server/commands/FillBiomeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/FillBiomeCommand.java
@@ -69,6 +69,12 @@ public class FillBiomeCommand {
         };
     }
 
+    // Folia start - region threading
+    private static void sendMessage(CommandSourceStack src, CommandSyntaxException ex) {
+        src.sendFailure((Component)ex.getRawMessage());
+    }
+    // Folia end - region threading
+
     private static int fill(CommandSourceStack source, BlockPos from, BlockPos to, Holder.Reference<Biome> biome, Predicate<Holder<Biome>> filter) throws CommandSyntaxException {
         BlockPos blockPos = quantize(from);
         BlockPos blockPos2 = quantize(to);
@@ -78,29 +84,43 @@ public class FillBiomeCommand {
             throw ERROR_VOLUME_TOO_LARGE.create(32768, i);
         } else {
             ServerLevel serverLevel = source.getLevel();
-            List<ChunkAccess> list = new ArrayList<>();
+            // Folia start - region threading
+            int buffer = 0;
+            // no buffer, we do not touch neighbours
+            serverLevel.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) -> {
+                    List<ChunkAccess> list = new ArrayList<>();
 
-            for(int j = SectionPos.blockToSectionCoord(boundingBox.minZ()); j <= SectionPos.blockToSectionCoord(boundingBox.maxZ()); ++j) {
-                for(int k = SectionPos.blockToSectionCoord(boundingBox.minX()); k <= SectionPos.blockToSectionCoord(boundingBox.maxX()); ++k) {
-                    ChunkAccess chunkAccess = serverLevel.getChunk(k, j, ChunkStatus.FULL, false);
-                    if (chunkAccess == null) {
-                        throw ERROR_NOT_LOADED.create();
-                    }
+                    for(int j = SectionPos.blockToSectionCoord(boundingBox.minZ()); j <= SectionPos.blockToSectionCoord(boundingBox.maxZ()); ++j) {
+                        for(int k = SectionPos.blockToSectionCoord(boundingBox.minX()); k <= SectionPos.blockToSectionCoord(boundingBox.maxX()); ++k) {
+                            ChunkAccess chunkAccess = serverLevel.getChunk(k, j, ChunkStatus.FULL, false);
+                            if (chunkAccess == null) {
+                                sendMessage(source, ERROR_NOT_LOADED.create()); return;
+                            }
 
-                    list.add(chunkAccess);
-                }
-            }
+                            list.add(chunkAccess);
+                        }
+                    }
 
-            MutableInt mutableInt = new MutableInt(0);
+                    MutableInt mutableInt = new MutableInt(0);
 
-            for(ChunkAccess chunkAccess2 : list) {
-                chunkAccess2.fillBiomesFromNoise(makeResolver(mutableInt, chunkAccess2, boundingBox, biome, filter), serverLevel.getChunkSource().randomState().sampler());
-                chunkAccess2.setUnsaved(true);
-                serverLevel.getChunkSource().chunkMap.resendChunk(chunkAccess2);
-            }
+                    for(ChunkAccess chunkAccess2 : list) {
+                        chunkAccess2.fillBiomesFromNoise(makeResolver(mutableInt, chunkAccess2, boundingBox, biome, filter), serverLevel.getChunkSource().randomState().sampler());
+                        chunkAccess2.setUnsaved(true);
+                        serverLevel.getChunkSource().chunkMap.resendChunk(chunkAccess2);
+                    }
 
-            source.sendSuccess(Component.translatable("commands.fillbiome.success.count", mutableInt.getValue(), boundingBox.minX(), boundingBox.minY(), boundingBox.minZ(), boundingBox.maxX(), boundingBox.maxY(), boundingBox.maxZ()), true);
-            return mutableInt.getValue();
+                    source.sendSuccess(Component.translatable("commands.fillbiome.success.count", mutableInt.getValue(), boundingBox.minX(), boundingBox.minY(), boundingBox.minZ(), boundingBox.maxX(), boundingBox.maxY(), boundingBox.maxZ()), true);
+                }
+            );
+            return 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 99fbb24dabe867ed4956a2996543107f58a57193..01360d24522a877bf7c3524f17ec65ef2b514b0c 100644
--- a/src/main/java/net/minecraft/server/commands/FillCommand.java
+++ b/src/main/java/net/minecraft/server/commands/FillCommand.java
@@ -57,6 +57,12 @@ 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 {
         int i = range.getXSpan() * range.getYSpan() * range.getZSpan();
         if (i > 32768) {
@@ -64,33 +70,50 @@ public class FillCommand {
         } else {
             List<BlockPos> list = Lists.newArrayList();
             ServerLevel serverLevel = source.getLevel();
-            int j = 0;
 
-            for(BlockPos blockPos : BlockPos.betweenClosed(range.minX(), range.minY(), range.minZ(), range.maxX(), range.maxY(), range.maxZ())) {
-                if (filter == null || filter.test(new BlockInWorld(serverLevel, blockPos, true))) {
-                    BlockInput blockInput = mode.filter.filter(range, blockPos, block, serverLevel);
-                    if (blockInput != null) {
-                        BlockEntity blockEntity = serverLevel.getBlockEntity(blockPos);
-                        Clearable.tryClear(blockEntity);
-                        if (blockInput.place(serverLevel, blockPos, 2)) {
-                            list.add(blockPos.immutable());
-                            ++j;
+            // 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) -> {
+                    int j = 0;
+
+                    for(BlockPos blockPos : BlockPos.betweenClosed(range.minX(), range.minY(), range.minZ(), range.maxX(), range.maxY(), range.maxZ())) {
+                        if (filter == null || filter.test(new BlockInWorld(serverLevel, blockPos, true))) {
+                            BlockInput blockInput = mode.filter.filter(range, blockPos, block, serverLevel);
+                            if (blockInput != null) {
+                                BlockEntity blockEntity = serverLevel.getBlockEntity(blockPos);
+                                Clearable.tryClear(blockEntity);
+                                if (blockInput.place(serverLevel, blockPos, 2)) {
+                                    list.add(blockPos.immutable());
+                                    ++j;
+                                }
+                            }
                         }
                     }
-                }
-            }
 
-            for(BlockPos blockPos2 : list) {
-                Block block2 = serverLevel.getBlockState(blockPos2).getBlock();
-                serverLevel.blockUpdated(blockPos2, block2);
-            }
+                    for(BlockPos blockPos2 : list) {
+                        Block block2 = serverLevel.getBlockState(blockPos2).getBlock();
+                        serverLevel.blockUpdated(blockPos2, block2);
+                    }
+
+                    if (j == 0) {
+                        sendMessage(source, ERROR_FAILED.create()); return; // Folia - region threading
+                    } else {
+                        source.sendSuccess(Component.translatable("commands.fill.success", j), true);
+                        return; // Folia - region threading
+                    }
+                }
+            );
 
-            if (j == 0) {
-                throw ERROR_FAILED.create();
-            } else {
-                source.sendSuccess(Component.translatable("commands.fill.success", j), true);
-                return j;
-            }
+            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 de484336165891d16220fdc0363e5283ba92b75d..3f165dbca5ce094ad39e46ecc2fa2bb9e80968ce 100644
--- a/src/main/java/net/minecraft/server/commands/ForceLoadCommand.java
+++ b/src/main/java/net/minecraft/server/commands/ForceLoadCommand.java
@@ -49,96 +49,126 @@ 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 {
         ChunkPos chunkPos = pos.toChunkPos();
         ServerLevel serverLevel = source.getLevel();
         ResourceKey<Level> resourceKey = serverLevel.dimension();
-        boolean bl = serverLevel.getForcedChunks().contains(chunkPos.toLong());
-        if (bl) {
-            source.sendSuccess(Component.translatable("commands.forceload.query.success", chunkPos, resourceKey.location()), false);
-            return 1;
-        } else {
-            throw ERROR_NOT_TICKING.create(chunkPos, resourceKey.location());
-        }
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> {
+            try {
+                boolean bl = serverLevel.getForcedChunks().contains(chunkPos.toLong());
+                if (bl) {
+                    source.sendSuccess(Component.translatable("commands.forceload.query.success", chunkPos, resourceKey.location()), false);
+                    return;
+                } else {
+                    throw ERROR_NOT_TICKING.create(chunkPos, resourceKey.location());
+                }
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
+            }
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int listForceLoad(CommandSourceStack source) {
         ServerLevel serverLevel = source.getLevel();
         ResourceKey<Level> resourceKey = serverLevel.dimension();
-        LongSet longSet = serverLevel.getForcedChunks();
-        int i = longSet.size();
-        if (i > 0) {
-            String string = Joiner.on(", ").join(longSet.stream().sorted().map(ChunkPos::new).map(ChunkPos::toString).iterator());
-            if (i == 1) {
-                source.sendSuccess(Component.translatable("commands.forceload.list.single", resourceKey.location(), string), false);
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> {
+            LongSet longSet = serverLevel.getForcedChunks();
+            int i = longSet.size();
+            if (i > 0) {
+                String string = Joiner.on(", ").join(longSet.stream().sorted().map(ChunkPos::new).map(ChunkPos::toString).iterator());
+                if (i == 1) {
+                    source.sendSuccess(Component.translatable("commands.forceload.list.single", resourceKey.location(), string), false);
+                } else {
+                    source.sendSuccess(Component.translatable("commands.forceload.list.multiple", i, resourceKey.location(), string), false);
+                }
             } else {
-                source.sendSuccess(Component.translatable("commands.forceload.list.multiple", i, resourceKey.location(), string), false);
+                source.sendFailure(Component.translatable("commands.forceload.added.none", resourceKey.location()));
             }
-        } else {
-            source.sendFailure(Component.translatable("commands.forceload.added.none", resourceKey.location()));
-        }
 
-        return i;
+        });
+        return 1;
+        // Folia end - region threading
     }
 
     private static int removeAll(CommandSourceStack source) {
         ServerLevel serverLevel = source.getLevel();
         ResourceKey<Level> resourceKey = serverLevel.dimension();
+        io.papermc.paper.threadedregions.RegionisedServer.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", resourceKey.location()), true);
+        }); // Folia - region threading
         return 0;
     }
 
     private static int changeForceLoad(CommandSourceStack source, ColumnPos from, ColumnPos to, boolean forceLoaded) throws CommandSyntaxException {
-        int i = Math.min(from.x(), to.x());
-        int j = Math.min(from.z(), to.z());
-        int k = Math.max(from.x(), to.x());
-        int l = Math.max(from.z(), to.z());
-        if (i >= -30000000 && j >= -30000000 && k < 30000000 && l < 30000000) {
-            int m = SectionPos.blockToSectionCoord(i);
-            int n = SectionPos.blockToSectionCoord(j);
-            int o = SectionPos.blockToSectionCoord(k);
-            int p = SectionPos.blockToSectionCoord(l);
-            long q = ((long)(o - m) + 1L) * ((long)(p - n) + 1L);
-            if (q > 256L) {
-                throw ERROR_TOO_MANY_CHUNKS.create(256, q);
-            } else {
-                ServerLevel serverLevel = source.getLevel();
-                ResourceKey<Level> resourceKey = serverLevel.dimension();
-                ChunkPos chunkPos = null;
-                int r = 0;
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> {
+            try {
+                int i = Math.min(from.x(), to.x());
+                int j = Math.min(from.z(), to.z());
+                int k = Math.max(from.x(), to.x());
+                int l = Math.max(from.z(), to.z());
+                if (i >= -30000000 && j >= -30000000 && k < 30000000 && l < 30000000) {
+                    int m = SectionPos.blockToSectionCoord(i);
+                    int n = SectionPos.blockToSectionCoord(j);
+                    int o = SectionPos.blockToSectionCoord(k);
+                    int p = SectionPos.blockToSectionCoord(l);
+                    long q = ((long)(o - m) + 1L) * ((long)(p - n) + 1L);
+                    if (q > 256L) {
+                        throw ERROR_TOO_MANY_CHUNKS.create(256, q);
+                    } else {
+                        ServerLevel serverLevel = source.getLevel();
+                        ResourceKey<Level> resourceKey = serverLevel.dimension();
+                        ChunkPos chunkPos = null;
+                        int r = 0;
 
-                for(int s = m; s <= o; ++s) {
-                    for(int t = n; t <= p; ++t) {
-                        boolean bl = serverLevel.setChunkForced(s, t, forceLoaded);
-                        if (bl) {
-                            ++r;
-                            if (chunkPos == null) {
-                                chunkPos = new ChunkPos(s, t);
+                        for(int s = m; s <= o; ++s) {
+                            for(int t = n; t <= p; ++t) {
+                                boolean bl = serverLevel.setChunkForced(s, t, forceLoaded);
+                                if (bl) {
+                                    ++r;
+                                    if (chunkPos == null) {
+                                        chunkPos = new ChunkPos(s, t);
+                                    }
+                                }
                             }
                         }
-                    }
-                }
 
-                if (r == 0) {
-                    throw (forceLoaded ? ERROR_ALL_ADDED : ERROR_NONE_REMOVED).create();
-                } else {
-                    if (r == 1) {
-                        source.sendSuccess(Component.translatable("commands.forceload." + (forceLoaded ? "added" : "removed") + ".single", chunkPos, resourceKey.location()), true);
-                    } else {
-                        ChunkPos chunkPos2 = new ChunkPos(m, n);
-                        ChunkPos chunkPos3 = new ChunkPos(o, p);
-                        source.sendSuccess(Component.translatable("commands.forceload." + (forceLoaded ? "added" : "removed") + ".multiple", r, resourceKey.location(), chunkPos2, chunkPos3), true);
-                    }
+                        if (r == 0) {
+                            throw (forceLoaded ? ERROR_ALL_ADDED : ERROR_NONE_REMOVED).create();
+                        } else {
+                            if (r == 1) {
+                                source.sendSuccess(Component.translatable("commands.forceload." + (forceLoaded ? "added" : "removed") + ".single", chunkPos, resourceKey.location()), true);
+                            } else {
+                                ChunkPos chunkPos2 = new ChunkPos(m, n);
+                                ChunkPos chunkPos3 = new ChunkPos(o, p);
+                                source.sendSuccess(Component.translatable("commands.forceload." + (forceLoaded ? "added" : "removed") + ".multiple", r, resourceKey.location(), chunkPos2, chunkPos3), true);
+                            }
 
-                    return r;
+                            return;
+                        }
+                    }
+                } else {
+                    throw BlockPosArgument.ERROR_OUT_OF_WORLD.create();
                 }
+            } catch (CommandSyntaxException ex) {
+                sendMessage(source, ex);
             }
-        } else {
-            throw BlockPosArgument.ERROR_OUT_OF_WORLD.create();
-        }
+        });
+        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 27c0aaf123c3e945eb24e8a3892bd8ac42115733..2f9f73e75b6c730a9cf327767ba1c34e34c64ed8 100644
--- a/src/main/java/net/minecraft/server/commands/GameModeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/GameModeCommand.java
@@ -44,15 +44,18 @@ public class GameModeCommand {
         int i = 0;
 
         for(ServerPlayer serverPlayer : targets) {
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
             // Paper start - extend 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
             }
+            }, 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 06e3a868e922f1b7a586d0ca28f64a67ae463b68..8f4a7b6ed27e97c22153dadf837e521a75bb6940 100644
--- a/src/main/java/net/minecraft/server/commands/GiveCommand.java
+++ b/src/main/java/net/minecraft/server/commands/GiveCommand.java
@@ -55,6 +55,7 @@ public class GiveCommand {
 
                     l -= i1;
                     ItemStack itemstack = item.createItemStack(i1, false);
+                    entityplayer.getBukkitEntity().taskScheduler.schedule((nmsEntity) -> { // Folia - region threading
                     boolean flag = entityplayer.getInventory().add(itemstack);
                     ItemEntity entityitem;
 
@@ -74,6 +75,7 @@ public class GiveCommand {
                             entityitem.setOwner(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 a6e4bd9243dab7feaed1bd968108a324d6c37ed7..4637e60292128e8c4053fb3a5fed48e53ec6553f 100644
--- a/src/main/java/net/minecraft/server/commands/KillCommand.java
+++ b/src/main/java/net/minecraft/server/commands/KillCommand.java
@@ -22,7 +22,9 @@ 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 6835072c6b30ee0b79c43e05526fd6d605bf7139..0a6baec737ef847fc84723176c7f267d3999ad4c 100644
--- a/src/main/java/net/minecraft/server/commands/PlaceCommand.java
+++ b/src/main/java/net/minecraft/server/commands/PlaceCommand.java
@@ -83,82 +83,130 @@ 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 serverLevel = source.getLevel();
         ConfiguredFeature<?, ?> configuredFeature = feature.value();
         ChunkPos chunkPos = new ChunkPos(pos);
         checkLoaded(serverLevel, new ChunkPos(chunkPos.x - 1, chunkPos.z - 1), new ChunkPos(chunkPos.x + 1, chunkPos.z + 1));
-        if (!configuredFeature.place(serverLevel, serverLevel.getChunkSource().getGenerator(), serverLevel.getRandom(), pos)) {
-            throw ERROR_FEATURE_FAILED.create();
-        } else {
-            String string = feature.key().location().toString();
-            source.sendSuccess(Component.translatable("commands.place.feature.success", string, pos.getX(), pos.getY(), pos.getZ()), true);
-            return 1;
-        }
+        // Folia start - region threading
+        serverLevel.loadChunksAsync(
+            pos, 16, net.minecraft.world.level.chunk.ChunkStatus.FULL,
+            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.NORMAL,
+            (chunks) -> {
+                try {
+                    if (!configuredFeature.place(serverLevel, serverLevel.getChunkSource().getGenerator(), serverLevel.getRandom(), pos)) {
+                        throw ERROR_FEATURE_FAILED.create();
+                    } else {
+                        String string = feature.key().location().toString();
+                        source.sendSuccess(Component.translatable("commands.place.feature.success", string, pos.getX(), pos.getY(), pos.getZ()), true);
+                    }
+                } 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 serverLevel = source.getLevel();
-        if (!JigsawPlacement.generateJigsaw(serverLevel, structurePool, id, maxDepth, pos, false)) {
-            throw ERROR_JIGSAW_FAILED.create();
-        } else {
-            source.sendSuccess(Component.translatable("commands.place.jigsaw.success", pos.getX(), pos.getY(), pos.getZ()), true);
-            return 1;
-        }
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+            serverLevel, pos.getX() >> 4, pos.getZ() >> 4, () -> {
+                try {
+                    if (!JigsawPlacement.generateJigsaw(serverLevel, structurePool, id, maxDepth, pos, false)) {
+                        throw ERROR_JIGSAW_FAILED.create();
+                    } else {
+                        source.sendSuccess(Component.translatable("commands.place.jigsaw.success", pos.getX(), pos.getY(), pos.getZ()), true);
+                    }
+                } 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 serverLevel = source.getLevel();
         Structure structure2 = structure.value();
         ChunkGenerator chunkGenerator = serverLevel.getChunkSource().getGenerator();
-        StructureStart structureStart = structure2.generate(source.registryAccess(), chunkGenerator, chunkGenerator.getBiomeSource(), serverLevel.getChunkSource().randomState(), serverLevel.getStructureManager(), serverLevel.getSeed(), new ChunkPos(pos), 0, serverLevel, (biome) -> {
-            return true;
-        });
-        if (!structureStart.isValid()) {
-            throw ERROR_STRUCTURE_FAILED.create();
-        } else {
-            BoundingBox boundingBox = structureStart.getBoundingBox();
-            ChunkPos chunkPos = new ChunkPos(SectionPos.blockToSectionCoord(boundingBox.minX()), SectionPos.blockToSectionCoord(boundingBox.minZ()));
-            ChunkPos chunkPos2 = new ChunkPos(SectionPos.blockToSectionCoord(boundingBox.maxX()), SectionPos.blockToSectionCoord(boundingBox.maxZ()));
-            checkLoaded(serverLevel, chunkPos, chunkPos2);
-            ChunkPos.rangeClosed(chunkPos, chunkPos2).forEach((chunkPosx) -> {
-                structureStart.placeInChunk(serverLevel, serverLevel.structureManager(), chunkGenerator, serverLevel.getRandom(), new BoundingBox(chunkPosx.getMinBlockX(), serverLevel.getMinBuildHeight(), chunkPosx.getMinBlockZ(), chunkPosx.getMaxBlockX(), serverLevel.getMaxBuildHeight(), chunkPosx.getMaxBlockZ()), chunkPosx);
-            });
-            String string = structure.key().location().toString();
-            source.sendSuccess(Component.translatable("commands.place.structure.success", string, pos.getX(), pos.getY(), pos.getZ()), true);
-            return 1;
-        }
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+            serverLevel, pos.getX() >> 4, pos.getZ() >> 4, () -> {
+                try {
+                    StructureStart structureStart = structure2.generate(source.registryAccess(), chunkGenerator, chunkGenerator.getBiomeSource(), serverLevel.getChunkSource().randomState(), serverLevel.getStructureManager(), serverLevel.getSeed(), new ChunkPos(pos), 0, serverLevel, (biome) -> {
+                        return true;
+                    });
+                    if (!structureStart.isValid()) {
+                        throw ERROR_STRUCTURE_FAILED.create();
+                    } else {
+                        BoundingBox boundingBox = structureStart.getBoundingBox();
+                        ChunkPos chunkPos = new ChunkPos(SectionPos.blockToSectionCoord(boundingBox.minX()), SectionPos.blockToSectionCoord(boundingBox.minZ()));
+                        ChunkPos chunkPos2 = new ChunkPos(SectionPos.blockToSectionCoord(boundingBox.maxX()), SectionPos.blockToSectionCoord(boundingBox.maxZ()));
+                        checkLoaded(serverLevel, chunkPos, chunkPos2);
+                        ChunkPos.rangeClosed(chunkPos, chunkPos2).forEach((chunkPosx) -> {
+                            structureStart.placeInChunk(serverLevel, serverLevel.structureManager(), chunkGenerator, serverLevel.getRandom(), new BoundingBox(chunkPosx.getMinBlockX(), serverLevel.getMinBuildHeight(), chunkPosx.getMinBlockZ(), chunkPosx.getMaxBlockX(), serverLevel.getMaxBuildHeight(), chunkPosx.getMaxBlockZ()), chunkPosx);
+                        });
+                        String string = structure.key().location().toString();
+                        source.sendSuccess(Component.translatable("commands.place.structure.success", string, pos.getX(), pos.getY(), pos.getZ()), true);
+                    }
+                } 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 serverLevel = source.getLevel();
-        StructureTemplateManager structureTemplateManager = serverLevel.getStructureManager();
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+            serverLevel, pos.getX() >> 4, pos.getZ() >> 4, () -> {
+                try {
+                    StructureTemplateManager structureTemplateManager = serverLevel.getStructureManager();
 
-        Optional<StructureTemplate> optional;
-        try {
-            optional = structureTemplateManager.get(id);
-        } catch (ResourceLocationException var13) {
-            throw ERROR_TEMPLATE_INVALID.create(id);
-        }
+                    Optional<StructureTemplate> optional;
+                    try {
+                        optional = structureTemplateManager.get(id);
+                    } catch (ResourceLocationException var13) {
+                        throw ERROR_TEMPLATE_INVALID.create(id);
+                    }
 
-        if (optional.isEmpty()) {
-            throw ERROR_TEMPLATE_INVALID.create(id);
-        } else {
-            StructureTemplate structureTemplate = optional.get();
-            checkLoaded(serverLevel, new ChunkPos(pos), new ChunkPos(pos.offset(structureTemplate.getSize())));
-            StructurePlaceSettings structurePlaceSettings = (new StructurePlaceSettings()).setMirror(mirror).setRotation(rotation);
-            if (integrity < 1.0F) {
-                structurePlaceSettings.clearProcessors().addProcessor(new BlockRotProcessor(integrity)).setRandom(StructureBlockEntity.createRandom((long)seed));
-            }
+                    if (optional.isEmpty()) {
+                        throw ERROR_TEMPLATE_INVALID.create(id);
+                    } else {
+                        StructureTemplate structureTemplate = optional.get();
+                        checkLoaded(serverLevel, new ChunkPos(pos), new ChunkPos(pos.offset(structureTemplate.getSize())));
+                        StructurePlaceSettings structurePlaceSettings = (new StructurePlaceSettings()).setMirror(mirror).setRotation(rotation);
+                        if (integrity < 1.0F) {
+                            structurePlaceSettings.clearProcessors().addProcessor(new BlockRotProcessor(integrity)).setRandom(StructureBlockEntity.createRandom((long)seed));
+                        }
 
-            boolean bl = structureTemplate.placeInWorld(serverLevel, pos, pos, structurePlaceSettings, StructureBlockEntity.createRandom((long)seed), 2);
-            if (!bl) {
-                throw ERROR_TEMPLATE_FAILED.create();
-            } else {
-                source.sendSuccess(Component.translatable("commands.place.template.success", id, pos.getX(), pos.getY(), pos.getZ()), true);
-                return 1;
+                        boolean bl = structureTemplate.placeInWorld(serverLevel, pos, pos, structurePlaceSettings, StructureBlockEntity.createRandom((long)seed), 2);
+                        if (!bl) {
+                            throw ERROR_TEMPLATE_FAILED.create();
+                        } else {
+                            source.sendSuccess(Component.translatable("commands.place.template.success", id, pos.getX(), pos.getY(), pos.getZ()), true);
+                        }
+                    }
+                } 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 2a92e542e4b3e4dfb26adfc4b21490a629b79382..d3405192a705637daba66735c717d64708362bd1 100644
--- a/src/main/java/net/minecraft/server/commands/RecipeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/RecipeCommand.java
@@ -36,7 +36,12 @@ 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) -> {
+                serverPlayer.awardRecipes(recipes);
+            }, null, 1L);
+            // Folia end - region threading
         }
 
         if (i == 0) {
@@ -56,7 +61,12 @@ 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) -> {
+                serverPlayer.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 ad435815e56ca5a8d5ea6046ee4a3ed4d3673a48..2e53969ae222c13a7ef034f96a7014f924960481 100644
--- a/src/main/java/net/minecraft/server/commands/SetBlockCommand.java
+++ b/src/main/java/net/minecraft/server/commands/SetBlockCommand.java
@@ -38,29 +38,45 @@ 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();
-        if (condition != null && !condition.test(new BlockInWorld(serverLevel, pos, true))) {
-            throw ERROR_FAILED.create();
-        } else {
-            boolean bl;
-            if (mode == SetBlockCommand.Mode.DESTROY) {
-                serverLevel.destroyBlock(pos, true);
-                bl = !block.getState().isAir() || !serverLevel.getBlockState(pos).isAir();
-            } else {
-                BlockEntity blockEntity = serverLevel.getBlockEntity(pos);
-                Clearable.tryClear(blockEntity);
-                bl = true;
-            }
+        // Folia start - region threading
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+            serverLevel, pos.getX() >> 4, pos.getZ() >> 4, () -> {
+                try {
+                    if (condition != null && !condition.test(new BlockInWorld(serverLevel, pos, true))) {
+                        throw ERROR_FAILED.create();
+                    } else {
+                        boolean bl;
+                        if (mode == SetBlockCommand.Mode.DESTROY) {
+                            serverLevel.destroyBlock(pos, true);
+                            bl = !block.getState().isAir() || !serverLevel.getBlockState(pos).isAir();
+                        } else {
+                            BlockEntity blockEntity = serverLevel.getBlockEntity(pos);
+                            Clearable.tryClear(blockEntity);
+                            bl = true;
+                        }
 
-            if (bl && !block.place(serverLevel, pos, 2)) {
-                throw ERROR_FAILED.create();
-            } else {
-                serverLevel.blockUpdated(pos, block.getState().getBlock());
-                source.sendSuccess(Component.translatable("commands.setblock.success", pos.getX(), pos.getY(), pos.getZ()), true);
-                return 1;
+                        if (bl && !block.place(serverLevel, pos, 2)) {
+                            throw ERROR_FAILED.create();
+                        } else {
+                            serverLevel.blockUpdated(pos, block.getState().getBlock());
+                            source.sendSuccess(Component.translatable("commands.setblock.success", pos.getX(), pos.getY(), pos.getZ()), true);
+                        }
+                    }
+                } 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 1e41de9523c5fa3b9cfced798a5c35a24ec9d349..aa2c3d3161d01c87cd88e3311907e6559e81aa4e 100644
--- a/src/main/java/net/minecraft/server/commands/SetSpawnCommand.java
+++ b/src/main/java/net/minecraft/server/commands/SetSpawnCommand.java
@@ -35,7 +35,12 @@ public class SetSpawnCommand {
         final Collection<ServerPlayer> actualTargets = new java.util.ArrayList<>(); // Paper
         for(ServerPlayer serverPlayer : targets) {
             // Paper start - PlayerSetSpawnEvent
-            if (serverPlayer.setRespawnPosition(resourceKey, pos, angle, true, false, com.destroystokyo.paper.event.player.PlayerSetSpawnEvent.Cause.COMMAND)) {
+            // Folia start - region threading
+            serverPlayer.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> {
+                player.setRespawnPosition(resourceKey, pos, angle, true, false, com.destroystokyo.paper.event.player.PlayerSetSpawnEvent.Cause.COMMAND);
+            }, null, 1L);
+            // Folia end - region threading
+            if (true) { // Folia - region threading
                 actualTargets.add(serverPlayer);
             }
             // Paper end
diff --git a/src/main/java/net/minecraft/server/commands/SummonCommand.java b/src/main/java/net/minecraft/server/commands/SummonCommand.java
index ade2626bc63f986a53277378cdc19f5366f9372f..b2081239f13d3a001bbfa467933518ec400baea7 100644
--- a/src/main/java/net/minecraft/server/commands/SummonCommand.java
+++ b/src/main/java/net/minecraft/server/commands/SummonCommand.java
@@ -63,11 +63,18 @@ 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.RegionisedServer.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 {
                     source.sendSuccess(Component.translatable("commands.summon.success", entity.getDisplayName()), true);
diff --git a/src/main/java/net/minecraft/server/commands/TeleportCommand.java b/src/main/java/net/minecraft/server/commands/TeleportCommand.java
index 027ca5b67c544048815ddef4bb36d0a8fc3d038c..f7981cc27aa62cf0935d6ce027cd73c50b837c04 100644
--- a/src/main/java/net/minecraft/server/commands/TeleportCommand.java
+++ b/src/main/java/net/minecraft/server/commands/TeleportCommand.java
@@ -78,7 +78,7 @@ 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(ClientboundPlayerPositionPacket.RelativeArgument.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) {
@@ -154,6 +154,24 @@ 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
             if (target instanceof ServerPlayer) {
                 ChunkPos chunkcoordintpair = new ChunkPos(new BlockPos(x, y, z));
 
diff --git a/src/main/java/net/minecraft/server/commands/TimeCommand.java b/src/main/java/net/minecraft/server/commands/TimeCommand.java
index f0a7a8df3caa2ea765bb0a87cfede71d0995d276..00f63992885c16ea01384fc00e1325f389cc1a0f 100644
--- a/src/main/java/net/minecraft/server/commands/TimeCommand.java
+++ b/src/main/java/net/minecraft/server/commands/TimeCommand.java
@@ -56,6 +56,7 @@ public class TimeCommand {
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
 
+            io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
             // CraftBukkit start
             TimeSkipEvent event = new TimeSkipEvent(worldserver.getWorld(), TimeSkipEvent.SkipReason.COMMAND, time - worldserver.getDayTime());
             Bukkit.getPluginManager().callEvent(event);
@@ -63,6 +64,7 @@ public class TimeCommand {
                 worldserver.setDayTime((long) worldserver.getDayTime() + event.getSkipAmount());
             }
             // CraftBukkit end
+            }); // Folia - region threading
         }
 
         source.sendSuccess(Component.translatable("commands.time.set", time), true);
@@ -75,6 +77,7 @@ public class TimeCommand {
         while (iterator.hasNext()) {
             ServerLevel worldserver = (ServerLevel) iterator.next();
 
+            io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
             // CraftBukkit start
             TimeSkipEvent event = new TimeSkipEvent(worldserver.getWorld(), TimeSkipEvent.SkipReason.COMMAND, time);
             Bukkit.getPluginManager().callEvent(event);
@@ -82,11 +85,14 @@ public class TimeCommand {
                 worldserver.setDayTime(worldserver.getDayTime() + event.getSkipAmount());
             }
             // CraftBukkit end
+            }); // Folia - region threading
         }
 
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
         int j = TimeCommand.getDayTime(source.getLevel());
 
         source.sendSuccess(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 71fd7887a4fa174d3f74c4bbe24497b156cbd3c8..b8e1054cd5c906fd425fe5987c10db963cb32c62 100644
--- a/src/main/java/net/minecraft/server/commands/WeatherCommand.java
+++ b/src/main/java/net/minecraft/server/commands/WeatherCommand.java
@@ -28,20 +28,26 @@ public class WeatherCommand {
     }
 
     private static int setClear(CommandSourceStack source, int duration) {
+        io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
         source.getLevel().setWeatherParameters(duration, 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.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
         source.getLevel().setWeatherParameters(0, 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.RegionisedServer.getInstance().addTask(() -> { // Folia - region threading
         source.getLevel().setWeatherParameters(0, 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/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index 51b3db0b6c2cede95b584268e035c0fb36d38094..48718c37e96821576f0d6bf0e510cd5806a23d4c 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -436,9 +436,9 @@ 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
@@ -741,6 +741,12 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
 
     @Override
     public String runCommand(String command) {
+        // Folia start - region threading
+        // RIP RCON
+        if (true) {
+            throw new UnsupportedOperationException();
+        }
+        // Folia end - region threading
         Waitable[] waitableArray = new Waitable[1];
         this.rconConsoleSource.prepareForCommand();
         this.executeBlocking(() -> {
diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index 0b9cb85c063f913ad9245bafb8587d2f06c0ac6e..179e142e7012eebbe636f65804f5ac6b8fb72abe 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -85,18 +85,18 @@ public class ChunkHolder {
     public void onChunkAdd() {
         // Paper start - optimise anyPlayerCloseEnoughForSpawning
         long key = io.papermc.paper.util.MCUtil.getCoordinateKey(this.pos);
-        this.playersInMobSpawnRange = this.chunkMap.playerMobSpawnMap.getObjectsInRange(key);
-        this.playersInChunkTickRange = this.chunkMap.playerChunkTickRangeMap.getObjectsInRange(key);
+        this.playersInMobSpawnRange = null; // Folia - region threading
+        this.playersInChunkTickRange = null; // Folia - region threading
         // Paper end - optimise anyPlayerCloseEnoughForSpawning
         // Paper start - optimise chunk tick iteration
         if (this.needsBroadcastChanges()) {
-            this.chunkMap.needsChangeBroadcasting.add(this);
+            this.chunkMap.level.getCurrentWorldData().addChunkHolderNeedsBroadcasting(this); // Folia - region threading
         }
         // Paper end - optimise chunk tick iteration
         // Paper start - optimise checkDespawn
         LevelChunk chunk = this.getFullChunkNowUnchecked();
         if (chunk != null) {
-            chunk.updateGeneralAreaCache();
+            //chunk.updateGeneralAreaCache(); // Folia - region threading
         }
         // Paper end - optimise checkDespawn
     }
@@ -108,13 +108,13 @@ public class ChunkHolder {
         // Paper end - optimise anyPlayerCloseEnoughForSpawning
         // Paper start - optimise chunk tick iteration
         if (this.needsBroadcastChanges()) {
-            this.chunkMap.needsChangeBroadcasting.remove(this);
+            this.chunkMap.level.getCurrentWorldData().removeChunkHolderNeedsBroadcasting(this); // Folia - region threading
         }
         // Paper end - optimise chunk tick iteration
         // Paper start - optimise checkDespawn
         LevelChunk chunk = this.getFullChunkNowUnchecked();
         if (chunk != null) {
-            chunk.removeGeneralAreaCache();
+            //chunk.removeGeneralAreaCache(); // Folia - region threading
         }
         // Paper end - optimise checkDespawn
     }
@@ -303,7 +303,7 @@ public class ChunkHolder {
 
     private void addToBroadcastMap() {
         org.spigotmc.AsyncCatcher.catchOp("ChunkHolder update");
-        this.chunkMap.needsChangeBroadcasting.add(this);
+        this.chunkMap.level.getCurrentWorldData().addChunkHolderNeedsBroadcasting(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 870f4d6fae8c14502b4653f246a2df9e345ccca3..e23d752fcf6fea08d3ec114b065ada9d7e634a80 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -146,21 +146,21 @@ 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;
     int viewDistance;
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobDistanceMap; // Paper
-    public final ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new ReferenceOpenHashSet<>();
+    //public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobDistanceMap; // Paper // Folia - region threading
+    //public final ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new ReferenceOpenHashSet<>(); // Folia - region threading
 
     // Paper - rewrite chunk system
     // Paper start - optimise checkDespawn
     public static final int GENERAL_AREA_MAP_SQUARE_RADIUS = 40;
     public static final double GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE = 16.0 * (GENERAL_AREA_MAP_SQUARE_RADIUS - 1);
     public static final double GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE_SQUARED = GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE * GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE;
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerGeneralAreaMap;
+    //public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerGeneralAreaMap; // Folia - region threading
     // Paper end - optimise checkDespawn
 
     // Paper start - distance maps
@@ -174,8 +174,8 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     // obviously this means a spawn range > 8 cannot be implemented
 
     // these maps are named after spigot's uses
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobSpawnMap; // this map is absent from updateMaps since it's controlled at the start of the chunkproviderserver tick
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerChunkTickRangeMap;
+    //public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobSpawnMap; // this map is absent from updateMaps since it's controlled at the start of the chunkproviderserver tick // Folia - region threading
+    //public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerChunkTickRangeMap; // Folia - region threading
     // Paper end - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
     // Paper start - use distance map to optimise tracker
     public static boolean isLegacyTrackingEntity(Entity entity) {
@@ -184,11 +184,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
 
     // 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];
-    }
+    // Folia - region threading
 
     private int convertSpigotRangeToVanilla(final int vanilla) {
         return MinecraftServer.getServer().getScaledTrackingDistance(vanilla);
@@ -200,40 +196,29 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         int chunkX = MCUtil.getChunkCoordinate(player.getX());
         int chunkZ = MCUtil.getChunkCoordinate(player.getZ());
         // Note: players need to be explicitly added to distance maps before they can be updated
-        this.playerChunkTickRangeMap.add(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE); // Paper - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
+        //this.playerChunkTickRangeMap.add(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE); // Paper - optimise ChunkMap#anyPlayerCloseEnoughForSpawning // Folia - region threading
         // Paper start - per player mob spawning
-        if (this.playerMobDistanceMap != null) {
-            this.playerMobDistanceMap.add(player, chunkX, chunkZ, io.papermc.paper.chunk.system.ChunkSystem.getTickViewDistance(player));
-        }
+        // Folia - region threading
         // Paper end - per player mob spawning
         // 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)));
-        }
+        // Folia - region threading
         // Paper end - use distance map to optimise entity tracker
-        this.playerGeneralAreaMap.add(player, chunkX, chunkZ, GENERAL_AREA_MAP_SQUARE_RADIUS); // Paper - optimise checkDespawn
+        //this.playerGeneralAreaMap.add(player, chunkX, chunkZ, GENERAL_AREA_MAP_SQUARE_RADIUS); // Paper - optimise checkDespawn // Folia - region threading
     }
 
     void removePlayerFromDistanceMaps(ServerPlayer player) {
         this.level.playerChunkLoader.removePlayer(player); // Paper - replace chunk loader
 
         // Paper start - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
-        this.playerMobSpawnMap.remove(player);
-        this.playerChunkTickRangeMap.remove(player);
+        this.level.getCurrentWorldData().mobSpawnMap.remove(player); // Folia - region threading
+        //this.playerChunkTickRangeMap.remove(player); // Folia - region threading
         // Paper end - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
-        this.playerGeneralAreaMap.remove(player); // Paper - optimise checkDespawns
+        //this.playerGeneralAreaMap.remove(player); // Paper - optimise checkDespawns // Folia - region threading
         // Paper start - per player mob spawning
-        if (this.playerMobDistanceMap != null) {
-            this.playerMobDistanceMap.remove(player);
-        }
+        // Folia - region threading
         // Paper end - per player mob spawning
         // 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);
-        }
+        // Folia - region threading
         // Paper end - use distance map to optimise tracker
     }
 
@@ -242,21 +227,14 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         int chunkZ = MCUtil.getChunkCoordinate(player.getZ());
         // Note: players need to be explicitly added to distance maps before they can be updated
         this.level.playerChunkLoader.updatePlayer(player); // Paper - replace chunk loader
-        this.playerChunkTickRangeMap.update(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE); // Paper - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
+        //this.playerChunkTickRangeMap.update(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE); // Paper - optimise ChunkMap#anyPlayerCloseEnoughForSpawning // Folia - region threading
         // Paper start - per player mob spawning
-        if (this.playerMobDistanceMap != null) {
-            this.playerMobDistanceMap.update(player, chunkX, chunkZ, io.papermc.paper.chunk.system.ChunkSystem.getTickViewDistance(player));
-        }
+        // Folia - region threading
         // Paper end - per player mob spawning
         // 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)));
-        }
+        // Folia - region threading
         // Paper end - use distance map to optimise entity tracker
-        this.playerGeneralAreaMap.update(player, chunkX, chunkZ, GENERAL_AREA_MAP_SQUARE_RADIUS); // Paper - optimise checkDespawn
+        //this.playerGeneralAreaMap.update(player, chunkX, chunkZ, GENERAL_AREA_MAP_SQUARE_RADIUS); // Paper - optimise checkDespawn // Folia - region threading
     }
     // Paper end
     // Paper start
@@ -294,8 +272,8 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         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();
@@ -340,96 +318,18 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.setViewDistance(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.regionManagers.add(this.dataRegionManager); // Folia - region threading
         // Paper end
-        this.playerMobDistanceMap = this.level.paperConfig().entities.spawning.perPlayerMobSpawns ? new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets) : null; // Paper
+        //this.playerMobDistanceMap = this.level.paperConfig().entities.spawning.perPlayerMobSpawns ? new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets) : null; // Paper // Folia - region threading
         // 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;
-                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 - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
-        this.playerChunkTickRangeMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets,
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                ChunkHolder playerChunk = ChunkMap.this.getUpdatingChunkIfPresent(MCUtil.getCoordinateKey(rangeX, rangeZ));
-                if (playerChunk != null) {
-                    playerChunk.playersInChunkTickRange = newState;
-                }
-            },
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                ChunkHolder playerChunk = ChunkMap.this.getUpdatingChunkIfPresent(MCUtil.getCoordinateKey(rangeX, rangeZ));
-                if (playerChunk != null) {
-                    playerChunk.playersInChunkTickRange = newState;
-                }
-            });
-        this.playerMobSpawnMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets,
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                ChunkHolder playerChunk = ChunkMap.this.getUpdatingChunkIfPresent(MCUtil.getCoordinateKey(rangeX, rangeZ));
-                if (playerChunk != null) {
-                    playerChunk.playersInMobSpawnRange = newState;
-                }
-            },
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                ChunkHolder playerChunk = ChunkMap.this.getUpdatingChunkIfPresent(MCUtil.getCoordinateKey(rangeX, rangeZ));
-                if (playerChunk != null) {
-                    playerChunk.playersInMobSpawnRange = newState;
-                }
-            });
+        // Folia - region threading
+        // Folia - region threading
         // Paper end - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
         // Paper start - optimise checkDespawn
-        this.playerGeneralAreaMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets,
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                LevelChunk chunk = ChunkMap.this.level.getChunkSource().getChunkAtIfCachedImmediately(rangeX, rangeZ);
-                if (chunk != null) {
-                    chunk.updateGeneralAreaCache(newState);
-                }
-            },
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                LevelChunk chunk = ChunkMap.this.level.getChunkSource().getChunkAtIfCachedImmediately(rangeX, rangeZ);
-                if (chunk != null) {
-                    chunk.updateGeneralAreaCache(newState);
-                }
-            });
+        // Folia - region threading
         // Paper end - optimise checkDespawn
     }
 
@@ -457,28 +357,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     // Paper start
-    public void updatePlayerMobTypeMap(Entity entity) {
-        if (!this.level.paperConfig().entities.spawning.perPlayerMobSpawns) {
-            return;
-        }
-        int index = entity.getType().getCategory().ordinal();
-
-        final com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> inRange = this.playerMobDistanceMap.getObjectsInRange(entity.chunkPosition());
-        if (inRange == null) {
-            return;
-        }
-        final Object[] backingSet = inRange.getBackingSet();
-        for (int i = 0; i < backingSet.length; i++) {
-            if (!(backingSet[i] instanceof final ServerPlayer player)) {
-                continue;
-            }
-            ++player.mobCounts[index];
-        }
-    }
-
-    public int getMobCountNear(ServerPlayer entityPlayer, net.minecraft.world.entity.MobCategory mobCategory) {
-        return entityPlayer.mobCounts[mobCategory.ordinal()];
-    }
+    // Folia - region threading - revert per player mob caps
     // Paper end
 
     private static double euclideanDistanceSquared(ChunkPos pos, Entity entity) {
@@ -747,6 +626,12 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     // Paper start
     // 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
@@ -1007,6 +892,38 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     final boolean anyPlayerCloseEnoughForSpawning(ChunkHolder playerchunk, 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
         // this function is so hot that removing the map lookup call can have an order of magnitude impact on its performance
         // tested and confirmed via System.nanoTime()
         com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> playersInRange = reducedRange ? playerchunk.playersInMobSpawnRange : playerchunk.playersInChunkTickRange;
@@ -1052,7 +969,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             return List.of();
         } else {
             Builder<ServerPlayer> builder = ImmutableList.builder();
-            Iterator iterator = this.playerMap.getPlayers(i).iterator();
+            Iterator iterator = this.level.getLocalPlayers().iterator(); // Folia - region threading
 
             while (iterator.hasNext()) {
                 ServerPlayer entityplayer = (ServerPlayer) iterator.next();
@@ -1081,25 +998,18 @@ 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);
-        int i = SectionPos.blockToSectionCoord(player.getBlockX());
-        int j = SectionPos.blockToSectionCoord(player.getBlockZ());
+        // Folia - region threading
 
         if (added) {
-            this.playerMap.addPlayer(ChunkPos.asLong(i, j), player, flag1);
+            // Folia - region threading
             this.updatePlayerPos(player);
-            if (!flag1) {
-                this.distanceManager.addPlayer(SectionPos.of((EntityAccess) player), player);
-            }
+            // Folia - region threading
             this.addPlayerToDistanceMaps(player); // Paper - distance maps
         } else {
             SectionPos sectionposition = player.getLastSectionPos();
 
-            this.playerMap.removePlayer(sectionposition.chunk().toLong(), player);
-            if (!flag2) {
-                this.distanceManager.removePlayer(sectionposition, player);
-            }
+            // Folia - region threading
+            // Folia - region threading
             this.removePlayerFromDistanceMaps(player); // Paper - distance maps
         }
 
@@ -1118,43 +1028,7 @@ 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
 
-        int i = SectionPos.blockToSectionCoord(player.getBlockX());
-        int j = SectionPos.blockToSectionCoord(player.getBlockZ());
-        SectionPos sectionposition = player.getLastSectionPos();
-        SectionPos sectionposition1 = SectionPos.of((EntityAccess) player);
-        long k = sectionposition.chunk().toLong();
-        long l = sectionposition1.chunk().toLong();
-        boolean flag = this.playerMap.ignored(player);
-        boolean flag1 = this.skipPlayer(player);
-        boolean flag2 = sectionposition.asLong() != sectionposition1.asLong();
-
-        if (flag2 || flag != flag1) {
-            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);
-            }
-
-            if (k != l) {
-                this.playerMap.updatePlayer(k, l, player);
-            }
-        }
-
-        int i1 = sectionposition.x();
-        int j1 = sectionposition.z();
-        int k1;
-        int l1;
+        // Folia - region threading - none of this logic is relevant anymore thanks to the player chunk loader
 
         // Paper - replaced by PlayerChunkLoader
 
@@ -1177,9 +1051,9 @@ 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;
         }
         if (entity instanceof ServerPlayer && ((ServerPlayer) entity).supressTrackerForLogin) return; // Delay adding to tracker until after list packets
@@ -1192,27 +1066,25 @@ 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()); // Paper - don't search all players // 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().getLocalEntities()) {
+                            if (possible.tracker != null) {
+                                possible.tracker.updatePlayer(entityplayer);
                             }
                         }
+                        // Folia end - region threading
                     }
 
                 }
@@ -1226,16 +1098,16 @@ 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();
@@ -1245,25 +1117,18 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
 
     // 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());
-            }
-        } finally {
-            this.level.timings.tracker1.stopTiming();
-        }
-
-
-        this.level.timings.tracker2.startTiming();
-        try {
-            for (TrackedEntity tracker : this.entityMap.values()) {
-                tracker.serverEntity.sendChanges();
+        // Folia start - region threading
+        List<ServerPlayer> players = this.level.getLocalPlayers(); // Folia - region threading
+        for (Entity entity : this.level.getCurrentWorldData().getLocalEntities()) {
+            TrackedEntity tracker = entity.tracker;
+            if (tracker == null) {
+                continue;
             }
-        } finally {
-            this.level.timings.tracker2.stopTiming();
+            tracker.updatePlayers(players);
+            tracker.removeNonTickThreadPlayers();
+            tracker.serverEntity.sendChanges();
         }
+        // Folia end - region threading
     }
     // Paper end - optimised tracker
 
@@ -1274,51 +1139,12 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             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
 
     }
 
     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);
@@ -1327,7 +1153,7 @@ 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);
@@ -1504,41 +1330,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             this.lastSectionPos = SectionPos.of((EntityAccess) entity);
         }
 
-        // Paper start - use distance map to optimise tracker
-        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> lastTrackerCandidates;
-
-        final void updatePlayers(com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newTrackerCandidates) {
-            com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> oldTrackerCandidates = this.lastTrackerCandidates;
-            this.lastTrackerCandidates = newTrackerCandidates;
-
-            if (newTrackerCandidates != null) {
-                Object[] rawData = newTrackerCandidates.getBackingSet();
-                for (int i = 0, len = rawData.length; i < len; ++i) {
-                    Object raw = rawData[i];
-                    if (!(raw instanceof ServerPlayer)) {
-                        continue;
-                    }
-                    ServerPlayer player = (ServerPlayer)raw;
-                    this.updatePlayer(player);
-                }
-            }
-
-            if (oldTrackerCandidates == newTrackerCandidates) {
-                // this is likely the case.
-                // means there has been no range changes, so we can just use the above for tracking.
-                return;
-            }
-
-            // stuff could have been removed, so we need to check the trackedPlayers set
-            // for players that were removed
-
-            for (ServerPlayerConnection conn : this.seenBy.toArray(new ServerPlayerConnection[0])) { // avoid CME
-                if (newTrackerCandidates == null || !newTrackerCandidates.contains(conn.getPlayer())) {
-                    this.updatePlayer(conn.getPlayer());
-                }
-            }
-        }
-        // Paper end - use distance map to optimise tracker
+        // Folia - region threading
 
         public boolean equals(Object object) {
             return object instanceof ChunkMap.TrackedEntity ? ((ChunkMap.TrackedEntity) object).entity.getId() == this.entity.getId() : false;
@@ -1585,6 +1377,28 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             }
 
         }
+        // Folia start - region threading
+        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);
+                }
+            }
+        }
+        // Folia end - region threading
 
         public void updatePlayer(ServerPlayer player) {
             org.spigotmc.AsyncCatcher.catchOp("player tracker update"); // Spigot
@@ -1600,10 +1414,15 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                 boolean flag = d1 <= d2 && this.entity.broadcastToPlayer(player);
 
                 // CraftBukkit start - respect vanish API
-                if (!player.getBukkitEntity().canSee(this.entity.getBukkitEntity())) {
+                if (!io.papermc.paper.util.TickThread.isTickThreadFor(player) || !player.getBukkitEntity().canSee(this.entity.getBukkitEntity())) { // Folia - region threading
                     flag = false;
                 }
                 // CraftBukkit end
+                // Folia start - region threading
+                if ((this.entity instanceof ServerPlayer thisEntity) && thisEntity.broadcastedDeath) {
+                    flag = false;
+                }
+                // Folia end - region threading
                 if (flag) {
                     if (this.seenBy.add(player.connection)) {
                         this.serverEntity.addPairing(player);
diff --git a/src/main/java/net/minecraft/server/level/DistanceManager.java b/src/main/java/net/minecraft/server/level/DistanceManager.java
index 88fca8b160df6804f30ed2cf8cf1f645085434e2..341650384498eebe3f7a3315c398bec994a3195b 100644
--- a/src/main/java/net/minecraft/server/level/DistanceManager.java
+++ b/src/main/java/net/minecraft/server/level/DistanceManager.java
@@ -200,14 +200,14 @@ public abstract class DistanceManager {
     public int getNaturalSpawnChunkCount() {
         // Paper start - use distance map to implement
         // note: this is the spawn chunk count
-        return this.chunkMap.playerChunkTickRangeMap.size();
+        return this.chunkMap.level.getCurrentWorldData().mobSpawnMap.size(); // Folia - region threading
         // Paper end - use distance map to implement
     }
 
     public boolean hasPlayersNearby(long chunkPos) {
         // Paper start - use distance map to implement
         // note: this is the is spawn chunk method
-        return this.chunkMap.playerChunkTickRangeMap.getObjectsInRange(chunkPos) != null;
+        return this.chunkMap.level.getCurrentWorldData().mobSpawnMap.getObjectsInRange(chunkPos) != null; // Folia - region threading
         // Paper end - use distance map to implement
     }
 
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index 736f37979c882e41e7571202df38eb6a2923fcb0..06ad3857f04ec073ae753b6569c5ae2ce7719ede 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -61,7 +61,7 @@ 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;
@@ -72,62 +72,33 @@ public class ServerChunkCache extends ChunkSource {
     @VisibleForDebug
     private NaturalSpawner.SpawnState lastSpawnState;
     // Paper start
-    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);
+    // Folia - region threading
+    final ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable<LevelChunk> loadedChunkMap = new ca.spottedleaf.concurrentutil.map.SWMRLong2ObjectHashTable<>(8192, 0.5f); // Folia - region threading
 
-    private final LevelChunk[] lastLoadedChunks = new LevelChunk[4 * 4];
+    // Folia - region threading
 
     private static int getChunkCacheKey(int x, int z) {
         return x & 3 | ((z & 3) << 2);
     }
 
     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) {
@@ -142,7 +113,7 @@ public class ServerChunkCache extends ChunkSource {
         return (LevelChunk)this.getChunk(x, z, ChunkStatus.FULL, true);
     }
 
-    long chunkFutureAwaitCounter; // Paper - private -> package private
+    final java.util.concurrent.atomic.AtomicLong chunkFutureAwaitCounter = new java.util.concurrent.atomic.AtomicLong(); // Paper - private -> package private // Folia - region threading - TODO MERGE INTO CHUNK SYSTEM PATCH
 
     public void getEntityTickingChunkAsync(int x, int z, java.util.function.Consumer<LevelChunk> onLoad) {
         io.papermc.paper.chunk.system.ChunkSystem.scheduleTickingState(
@@ -293,8 +264,7 @@ public class ServerChunkCache extends ChunkSource {
         this.distanceManager.removeTicket(ticketType, chunkPos, ticketLevel, identifier);
     }
 
-    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
     // 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) {
@@ -368,26 +338,7 @@ 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
     // Paper start - async chunk io
@@ -483,6 +434,7 @@ 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;
 
@@ -659,10 +611,11 @@ public class ServerChunkCache extends ChunkSource {
     }
 
     private void tickChunks() {
+        io.papermc.paper.threadedregions.RegionisedWorldData regionisedWorldData = this.level.getCurrentWorldData(); // Folia - region threading
         long i = this.level.getGameTime();
-        long j = i - this.lastInhabitedUpdate;
+        long j = 1; // Folia - region threading
 
-        this.lastInhabitedUpdate = i;
+        //this.lastInhabitedUpdate = i; // Folia - region threading
         boolean flag = this.level.isDebug();
 
         if (flag) {
@@ -670,9 +623,11 @@ public class ServerChunkCache extends ChunkSource {
         } else {
             // Paper start - optimize isOutisdeRange
             ChunkMap playerChunkMap = this.chunkMap;
-            for (ServerPlayer player : this.level.players) {
+            // Folia - region threading
+
+            for (ServerPlayer player : this.level.getLocalPlayers()) { // Folia - region threading
                 if (!player.affectsSpawning || player.isSpectator()) {
-                    playerChunkMap.playerMobSpawnMap.remove(player);
+                    regionisedWorldData.mobSpawnMap.remove(player); // Folia - region threading
                     continue;
                 }
 
@@ -685,8 +640,9 @@ 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.playerChunkTickRangeMap.getLastViewDistance(player) == -1) {
-                    playerChunkMap.playerMobSpawnMap.remove(player);
+                if (event.isCancelled() || event.getSpawnRadius() < 0) { // Folia - region threading
+                    player.lastEntitySpawnRadiusSquared = -1.0; player.playerNaturallySpawnedEvent = null;  // Folia - region threading
+                    regionisedWorldData.mobSpawnMap.remove(player); // Folia - region threading
                     continue;
                 }
 
@@ -694,7 +650,7 @@ public class ServerChunkCache extends ChunkSource {
                 int chunkX = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getX());
                 int chunkZ = io.papermc.paper.util.MCUtil.getChunkCoordinate(player.getZ());
 
-                playerChunkMap.playerMobSpawnMap.addOrUpdate(player, chunkX, chunkZ, range);
+                regionisedWorldData.mobSpawnMap.addOrUpdate(player, chunkX, chunkZ, range); // Folia - region threading
                 player.lastEntitySpawnRadiusSquared = (double)((range << 4) * (range << 4)); // used in anyPlayerCloseEnoughForSpawning
                 player.playerNaturallySpawnedEvent = event;
             }
@@ -704,23 +660,16 @@ public class ServerChunkCache extends ChunkSource {
 
             gameprofilerfiller.push("pollingChunks");
             int k = this.level.getGameRules().getInt(GameRules.RULE_RANDOMTICKING);
-            boolean flag1 = level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) != 0L && worlddata.getGameTime() % level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) == 0L; // CraftBukkit
+            boolean flag1 = level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) != 0L && this.level.getRedstoneGameTime() % level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) == 0L; // CraftBukkit // Folia - region threading
 
             gameprofilerfiller.push("naturalSpawnCount");
             this.level.timings.countNaturalMobs.startTiming(); // Paper - timings
             int l = this.distanceManager.getNaturalSpawnChunkCount();
             // Paper start - per player mob spawning
             NaturalSpawner.SpawnState spawnercreature_d; // moved down
-            if ((this.spawnFriendlies || this.spawnEnemies) && this.chunkMap.playerMobDistanceMap != null) { // don't count mobs when animals and monsters are disabled
-                // re-set mob counts
-                for (ServerPlayer player : this.level.players) {
-                    Arrays.fill(player.mobCounts, 0);
-                }
-                spawnercreature_d = NaturalSpawner.createState(l, this.level.getAllEntities(), this::getFullChunk, null, true);
-            } else {
-                spawnercreature_d = NaturalSpawner.createState(l, this.level.getAllEntities(), this::getFullChunk, this.chunkMap.playerMobDistanceMap == null ? new LocalMobCapCalculator(this.chunkMap) : null, false);
-            }
-            // Paper end
+            // Folia start - threaded regions - revert per-player mob caps
+            spawnercreature_d = this.spawnFriendlies || this.spawnEnemies ? NaturalSpawner.createState(l, this.level.getAllEntities(), this::getFullChunk, new LocalMobCapCalculator(this.chunkMap)) : null;
+            // Folia end - threaded regions - revert per-player mob caps
             this.level.timings.countNaturalMobs.stopTiming(); // Paper - timings
 
             this.lastSpawnState = spawnercreature_d;
@@ -731,17 +680,17 @@ public class ServerChunkCache extends ChunkSource {
             // Paper - moved down
 
             gameprofilerfiller.popPush("spawnAndTick");
-            boolean flag2 = this.level.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && !this.level.players().isEmpty(); // CraftBukkit
+            boolean flag2 = this.level.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && !regionisedWorldData.getLocalPlayers().isEmpty(); // CraftBukkit // Folia - region threading
 
             // Paper - only shuffle if per-player mob spawning is disabled
             // Paper - moved natural spawn event up
             // Paper start - optimise chunk tick iteration
             Iterator<LevelChunk> iterator1;
-            if (this.level.paperConfig().entities.spawning.perPlayerMobSpawns) {
-                iterator1 = this.entityTickingChunks.iterator();
+            if (true) { // Folia - region threading - revert per player mob caps, except for this - WTF are they doing?
+                iterator1 = regionisedWorldData.getEntityTickingChunks().iterator(); // Folia - region threading
             } else {
-                iterator1 = this.entityTickingChunks.unsafeIterator();
-                List<LevelChunk> shuffled = Lists.newArrayListWithCapacity(this.entityTickingChunks.size());
+                iterator1 = regionisedWorldData.getEntityTickingChunks().unsafeIterator(); // Folia - region threading
+                List<LevelChunk> shuffled = Lists.newArrayListWithCapacity(regionisedWorldData.getEntityTickingChunks().size()); // Folia - region threading
                 while (iterator1.hasNext()) {
                     shuffled.add(iterator1.next());
                 }
@@ -791,14 +740,14 @@ public class ServerChunkCache extends ChunkSource {
             // Paper start - use set of chunks requiring updates, rather than iterating every single one loaded
             gameprofilerfiller.popPush("broadcast");
             this.level.timings.broadcastChunkUpdates.startTiming(); // Paper - timing
-            if (!this.chunkMap.needsChangeBroadcasting.isEmpty()) {
-                ReferenceOpenHashSet<ChunkHolder> copy = this.chunkMap.needsChangeBroadcasting.clone();
-                this.chunkMap.needsChangeBroadcasting.clear();
+            if (!regionisedWorldData.getNeedsChangeBroadcasting().isEmpty()) { // Folia - region threading
+                ReferenceOpenHashSet<ChunkHolder> copy = regionisedWorldData.getNeedsChangeBroadcasting().clone(); // Folia - region threading
+                regionisedWorldData.getNeedsChangeBroadcasting().clear(); // Folia - region threading
                 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);
+                        regionisedWorldData.getNeedsChangeBroadcasting().add(holder); // Folia - region threading
                     }
                 }
             }
@@ -806,8 +755,8 @@ public class ServerChunkCache extends ChunkSource {
             gameprofilerfiller.pop();
             // Paper end - use set of chunks requiring updates, rather than iterating every single one loaded
             // Paper start - controlled flush for entity tracker packets
-            List<net.minecraft.network.Connection> disabledFlushes = new java.util.ArrayList<>(this.level.players.size());
-            for (ServerPlayer player : this.level.players) {
+            List<net.minecraft.network.Connection> disabledFlushes = new java.util.ArrayList<>(regionisedWorldData.getLocalPlayers().size()); // Folia - region threading
+            for (ServerPlayer player : regionisedWorldData.getLocalPlayers()) { // Folia - region threading
                 net.minecraft.server.network.ServerGamePacketListenerImpl connection = player.connection;
                 if (connection != null) {
                     connection.connection.disableAutomaticFlush();
@@ -880,14 +829,19 @@ 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.RegionisedServer.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) {
@@ -992,8 +946,43 @@ 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);
         }
@@ -1001,11 +990,16 @@ 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.getCurrentRegionisedWorldData().world) {
+                throw new IllegalStateException("Polling tasks from non-owned region");
+            }
+            // Folia end - region threading
             ServerChunkCache.this.chunkMap.level.playerChunkLoader.tickMidTick(); // Paper - replace player chunk loader
             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 714637cdd9dcdbffa344b19e77944fb3c7541ff7..61fd4eea649fab254b3b2c0f160257e01d0873ed 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -192,35 +192,34 @@ 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 final EndDragonFight dragonFight;
     final Int2ObjectMap<EnderDragonPart> dragonParts;
     private final StructureManager structureManager;
     private final StructureCheck structureCheck;
-    private final boolean tickTime;
-    public long lastMidTickExecuteFailure; // Paper - execute chunk tasks mid tick
+    public final boolean tickTime; // Folia - region threading
+    // Folia - region threading
 
     // CraftBukkit start
     public final LevelStorageSource.LevelStorageAccess convertable;
     public final UUID uuid;
-    public boolean hasPhysicsEvent = true; // Paper
-    public boolean hasEntityMoveEvent = false; // Paper
+    // Folia - region threading
     private final alternate.current.wire.WireHandler wireHandler = new alternate.current.wire.WireHandler(this); // Paper - optimize redstone (Alternate Current)
     public static Throwable getAddToWorldStackTrace(Entity entity) {
         final Throwable thr = new Throwable(entity + " Added to world at " + new java.util.Date());
@@ -267,50 +266,64 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return true;
     }
 
-    public final void loadChunksForMoveAsync(AABB axisalignedbb, ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority priority,
-                                             java.util.function.Consumer<List<net.minecraft.world.level.chunk.ChunkAccess>> onLoad) {
-        if (Thread.currentThread() != this.thread) {
-            this.getChunkSource().mainThreadProcessor.execute(() -> {
-                this.loadChunksForMoveAsync(axisalignedbb, priority, onLoad);
-            });
-            return;
-        }
+    // Folia start - region threading - TODO rebase
+    public final void loadChunksAsync(BlockPos pos, int radiusBlocks,
+                                      ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority priority,
+                                      java.util.function.Consumer<List<net.minecraft.world.level.chunk.ChunkAccess>> onLoad) {
+        loadChunksAsync(
+            (pos.getX() - radiusBlocks) >> 4,
+            (pos.getX() + radiusBlocks) >> 4,
+            (pos.getZ() - radiusBlocks) >> 4,
+            (pos.getZ() + radiusBlocks) >> 4,
+            priority, onLoad
+        );
+    }
+
+    public final void loadChunksAsync(BlockPos pos, int radiusBlocks,
+                                      net.minecraft.world.level.chunk.ChunkStatus chunkStatus,
+                                      ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority priority,
+                                      java.util.function.Consumer<List<net.minecraft.world.level.chunk.ChunkAccess>> onLoad) {
+        loadChunksAsync(
+            (pos.getX() - radiusBlocks) >> 4,
+            (pos.getX() + radiusBlocks) >> 4,
+            (pos.getZ() - radiusBlocks) >> 4,
+            (pos.getZ() + radiusBlocks) >> 4,
+            chunkStatus, priority, onLoad
+        );
+    }
+
+    public final void loadChunksAsync(int minChunkX, int maxChunkX, int minChunkZ, int maxChunkZ,
+                                      ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority priority,
+                                      java.util.function.Consumer<List<net.minecraft.world.level.chunk.ChunkAccess>> onLoad) {
+        this.loadChunksAsync(minChunkX, maxChunkX, minChunkZ, maxChunkZ, net.minecraft.world.level.chunk.ChunkStatus.FULL, priority, onLoad);
+    }
+
+    public final void loadChunksAsync(int minChunkX, int maxChunkX, int minChunkZ, int maxChunkZ,
+                                      net.minecraft.world.level.chunk.ChunkStatus chunkStatus,
+                                      ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority priority,
+                                      java.util.function.Consumer<List<net.minecraft.world.level.chunk.ChunkAccess>> onLoad) {
         List<net.minecraft.world.level.chunk.ChunkAccess> ret = new java.util.ArrayList<>();
-        IntArrayList ticketLevels = new IntArrayList();
-
-        int minBlockX = Mth.floor(axisalignedbb.minX - 1.0E-7D) - 3;
-        int maxBlockX = Mth.floor(axisalignedbb.maxX + 1.0E-7D) + 3;
-
-        int minBlockZ = Mth.floor(axisalignedbb.minZ - 1.0E-7D) - 3;
-        int maxBlockZ = Mth.floor(axisalignedbb.maxZ + 1.0E-7D) + 3;
-
-        int minChunkX = minBlockX >> 4;
-        int maxChunkX = maxBlockX >> 4;
-
-        int minChunkZ = minBlockZ >> 4;
-        int maxChunkZ = maxBlockZ >> 4;
 
         ServerChunkCache chunkProvider = this.getChunkSource();
 
         int requiredChunks = (maxChunkX - minChunkX + 1) * (maxChunkZ - minChunkZ + 1);
-        int[] loadedChunks = new int[1];
+        java.util.concurrent.atomic.AtomicInteger loadedChunks = new java.util.concurrent.atomic.AtomicInteger();
+
+        Long holderIdentifier = Long.valueOf(chunkProvider.chunkFutureAwaitCounter.getAndIncrement());
 
-        Long holderIdentifier = Long.valueOf(chunkProvider.chunkFutureAwaitCounter++);
+        int ticketLevel = 33 + net.minecraft.world.level.chunk.ChunkStatus.getDistance(chunkStatus);
 
         java.util.function.Consumer<net.minecraft.world.level.chunk.ChunkAccess> consumer = (net.minecraft.world.level.chunk.ChunkAccess chunk) -> {
             if (chunk != null) {
-                int ticketLevel = Math.max(33, chunkProvider.chunkMap.getUpdatingChunkIfPresent(chunk.getPos().toLong()).getTicketLevel());
                 ret.add(chunk);
-                ticketLevels.add(ticketLevel);
                 chunkProvider.addTicketAtLevel(TicketType.FUTURE_AWAIT, chunk.getPos(), ticketLevel, holderIdentifier);
             }
-            if (++loadedChunks[0] == requiredChunks) {
+            if (loadedChunks.incrementAndGet() == requiredChunks) {
                 try {
                     onLoad.accept(java.util.Collections.unmodifiableList(ret));
                 } finally {
                     for (int i = 0, len = ret.size(); i < len; ++i) {
                         ChunkPos chunkPos = ret.get(i).getPos();
-                        int ticketLevel = ticketLevels.getInt(i);
 
                         chunkProvider.addTicketAtLevel(TicketType.UNKNOWN, chunkPos, ticketLevel, chunkPos);
                         chunkProvider.removeTicketAtLevel(TicketType.FUTURE_AWAIT, chunkPos, ticketLevel, holderIdentifier);
@@ -322,11 +335,31 @@ public class ServerLevel extends Level implements WorldGenLevel {
         for (int cx = minChunkX; cx <= maxChunkX; ++cx) {
             for (int cz = minChunkZ; cz <= maxChunkZ; ++cz) {
                 io.papermc.paper.chunk.system.ChunkSystem.scheduleChunkLoad(
-                    this, cx, cz, net.minecraft.world.level.chunk.ChunkStatus.FULL, true, priority, consumer
+                    this, cx, cz, chunkStatus, true, priority, consumer
                 );
             }
         }
     }
+    // Folia end - region threading - TODO rebase
+
+    public final void loadChunksForMoveAsync(AABB axisalignedbb, ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority priority,
+                                             java.util.function.Consumer<List<net.minecraft.world.level.chunk.ChunkAccess>> onLoad) {
+        // Folia - region threading - TODO MERGE INTO CHUNK SYSTEM PATCH
+
+        int minBlockX = Mth.floor(axisalignedbb.minX - 1.0E-7D) - 3;
+        int maxBlockX = Mth.floor(axisalignedbb.maxX + 1.0E-7D) + 3;
+
+        int minBlockZ = Mth.floor(axisalignedbb.minZ - 1.0E-7D) - 3;
+        int maxBlockZ = Mth.floor(axisalignedbb.maxZ + 1.0E-7D) + 3;
+
+        int minChunkX = minBlockX >> 4;
+        int maxChunkX = maxBlockX >> 4;
+
+        int minChunkZ = minBlockZ >> 4;
+        int maxChunkZ = maxBlockZ >> 4;
+
+        this.loadChunksAsync(minChunkX, maxChunkX, minChunkZ, maxChunkZ, priority, onLoad); // Folia - region threading - move into own function TODO rebase
+    }
 
     // Paper start - rewrite chunk system
     public final io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler chunkTaskScheduler;
@@ -446,81 +479,16 @@ public class ServerLevel extends Level implements WorldGenLevel {
     // Paper end
 
     // Paper start - optimise checkDespawn
-    public final List<ServerPlayer> playersAffectingSpawning = new java.util.ArrayList<>();
+    // Folia - region threading
     // Paper end - optimise checkDespawn
     // Paper start - optimise get nearest players for entity AI
-    @Override
-    public final ServerPlayer getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions condition, @Nullable LivingEntity source,
-                                               double centerX, double centerY, double centerZ) {
-        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearby;
-        nearby = this.getChunkSource().chunkMap.playerGeneralAreaMap.getObjectsInRange(Mth.floor(centerX) >> 4, Mth.floor(centerZ) >> 4);
-
-        if (nearby == null) {
-            return null;
-        }
-
-        Object[] backingSet = nearby.getBackingSet();
-
-        double closestDistanceSquared = Double.MAX_VALUE;
-        ServerPlayer closest = null;
-
-        for (int i = 0, len = backingSet.length; i < len; ++i) {
-            Object _player = backingSet[i];
-            if (!(_player instanceof ServerPlayer)) {
-                continue;
-            }
-            ServerPlayer player = (ServerPlayer)_player;
-
-            double distanceSquared = player.distanceToSqr(centerX, centerY, centerZ);
-            if (distanceSquared < closestDistanceSquared && condition.test(source, player)) {
-                closest = player;
-                closestDistanceSquared = distanceSquared;
-            }
-        }
-
-        return closest;
-    }
+    // Folia - region threading
 
-    @Override
-    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions pathfindertargetcondition, LivingEntity entityliving) {
-        return this.getNearestPlayer(pathfindertargetcondition, entityliving, entityliving.getX(), entityliving.getY(), entityliving.getZ());
-    }
-
-    @Override
-    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions pathfindertargetcondition,
-                                   double d0, double d1, double d2) {
-        return this.getNearestPlayer(pathfindertargetcondition, null, d0, d1, d2);
-    }
+    // Folia - region threading
 
-    @Override
-    public List<Player> getNearbyPlayers(net.minecraft.world.entity.ai.targeting.TargetingConditions condition, LivingEntity source, AABB axisalignedbb) {
-        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearby;
-        double centerX = (axisalignedbb.maxX + axisalignedbb.minX) * 0.5;
-        double centerZ = (axisalignedbb.maxZ + axisalignedbb.minZ) * 0.5;
-        nearby = this.getChunkSource().chunkMap.playerGeneralAreaMap.getObjectsInRange(Mth.floor(centerX) >> 4, Mth.floor(centerZ) >> 4);
-
-        List<Player> ret = new java.util.ArrayList<>();
-
-        if (nearby == null) {
-            return ret;
-        }
-
-        Object[] backingSet = nearby.getBackingSet();
-
-        for (int i = 0, len = backingSet.length; i < len; ++i) {
-            Object _player = backingSet[i];
-            if (!(_player instanceof ServerPlayer)) {
-                continue;
-            }
-            ServerPlayer player = (ServerPlayer)_player;
-
-            if (axisalignedbb.contains(player.getX(), player.getY(), player.getZ()) && condition.test(source, player)) {
-                ret.add(player);
-            }
-        }
+    // Folia - region threading
 
-        return ret;
-    }
+    // Folia - region threading
     // Paper end - optimise get nearest players for entity AI
 
     public final io.papermc.paper.chunk.system.RegionisedPlayerChunkLoader playerChunkLoader = new io.papermc.paper.chunk.system.RegionisedPlayerChunkLoader(this);
@@ -565,6 +533,29 @@ public class ServerLevel extends Level implements WorldGenLevel {
         });
     }
 
+    // Folia start - regionised ticking
+    public final io.papermc.paper.threadedregions.TickRegions tickRegions = new io.papermc.paper.threadedregions.TickRegions();
+    public final io.papermc.paper.threadedregions.ThreadedRegioniser<io.papermc.paper.threadedregions.TickRegions.TickRegionData, io.papermc.paper.threadedregions.TickRegions.TickRegionSectionData> regioniser;
+    {
+        this.regioniser = new io.papermc.paper.threadedregions.ThreadedRegioniser<>(
+            3*9,
+            (2.0 / 3.0),
+            1,
+            1,
+            io.papermc.paper.threadedregions.TickRegions.getRegionChunkShift(),
+            this,
+            this.tickRegions
+        );
+    }
+    public final io.papermc.paper.threadedregions.RegionisedTaskQueue.WorldRegionTaskData taskQueueRegionData = new io.papermc.paper.threadedregions.RegionisedTaskQueue.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;
+
+    // Folia end - regionised ticking
+
     // 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, org.bukkit.World.Environment env, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider) {
         // Holder holder = worlddimension.type(); // CraftBukkit - decompile error
@@ -574,13 +565,13 @@ 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;
@@ -619,7 +610,7 @@ 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((nbttagcompound) -> {
@@ -647,8 +638,15 @@ 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.RegionisedServer.WorldLevelData(this, this.serverLevelData.getGameTime(), this.serverLevelData.getDayTime());
+    }
+    // Folia end - region threading
+
     public void setWeatherParameters(int clearDuration, int rainDuration, boolean raining, boolean thundering) {
         this.serverLevelData.setClearWeatherTime(clearDuration);
         this.serverLevelData.setRainTime(rainDuration);
@@ -666,55 +664,31 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return this.structureManager;
     }
 
-    public void tick(BooleanSupplier shouldKeepTicking) {
-        // Paper start - optimise checkDespawn
-        this.playersAffectingSpawning.clear();
-        for (ServerPlayer player : this.players) {
-            if (net.minecraft.world.entity.EntitySelector.PLAYER_AFFECTS_SPAWNING.test(player)) {
-                this.playersAffectingSpawning.add(player);
-            }
-        }
-        // Paper end - optimise checkDespawn
+    public void tick(BooleanSupplier shouldKeepTicking, io.papermc.paper.threadedregions.TickRegions.TickRegionData region) { // Folia - regionised ticking
+        final io.papermc.paper.threadedregions.RegionisedWorldData regionisedWorldData = this.getCurrentWorldData(); // Folia - regionised ticking
+        // Folia - region threading
         ProfilerFiller gameprofilerfiller = this.getProfiler();
 
-        this.handlingTick = true;
+        regionisedWorldData.setHandlingTick(true); // Folia - regionised ticking
         gameprofilerfiller.push("world border");
-        this.getWorldBorder().tick();
+        if (region == null) this.getWorldBorder().tick(); // Folia - regionised ticking - moved into global tick
         gameprofilerfiller.popPush("weather");
-        this.advanceWeatherCycle();
-        int i = this.getGameRules().getInt(GameRules.RULE_PLAYERS_SLEEPING_PERCENTAGE);
+        if (region == null) this.advanceWeatherCycle();
+        //int i = this.getGameRules().getInt(GameRules.RULE_PLAYERS_SLEEPING_PERCENTAGE); // Folia - region threading - move intotickSleep
         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)) {
-                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
         this.tickTime();
         gameprofilerfiller.popPush("tickPending");
         timings.scheduledBlocks.startTiming(); // Paper
         if (!this.isDebug()) {
-            j = this.getGameTime();
+            j = regionisedWorldData.getRedstoneGameTime(); // Folia - region threading
             gameprofilerfiller.push("blockTicks");
-            this.blockTicks.tick(j, 65536, this::tickBlock);
+            regionisedWorldData.getBlockLevelTicks().tick(j, 65536, this::tickBlock); // Folia - region ticking
             gameprofilerfiller.popPush("fluidTicks");
-            this.fluidTicks.tick(j, 65536, this::tickFluid);
+            regionisedWorldData.getFluidLevelTicks().tick(j, 65536, this::tickFluid); // Folia - region ticking
             gameprofilerfiller.pop();
         }
         timings.scheduledBlocks.stopTiming(); // Paper
@@ -731,7 +705,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         timings.doSounds.startTiming(); // Spigot
         this.runBlockEvents();
         timings.doSounds.stopTiming(); // Spigot
-        this.handlingTick = false;
+        regionisedWorldData.setHandlingTick(false); // Folia - regionised ticking
         gameprofilerfiller.pop();
         boolean flag = true || !this.players.isEmpty() || !this.getForcedChunks().isEmpty(); // CraftBukkit - this prevents entity cleanup, other issues on servers with no players
 
@@ -743,20 +717,30 @@ public class ServerLevel extends Level implements WorldGenLevel {
             gameprofilerfiller.push("entities");
             timings.tickEntities.startTiming(); // Spigot
             if (this.dragonFight != null) {
+                if (io.papermc.paper.util.TickThread.isTickThreadFor(this, 0, 0)) { // 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(0, 0);
+                    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
             timings.entityTick.startTiming(); // Spigot
-            this.entityTickList.forEach((entity) -> {
+            regionisedWorldData.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 {
                         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();
@@ -787,6 +771,31 @@ 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)) { // Folia - region threading - moved to global tick
+            // 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)) {
+                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
@@ -797,11 +806,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
 
     protected void tickTime() {
         if (this.tickTime) {
-            long i = this.levelData.getGameTime() + 1L;
+            io.papermc.paper.threadedregions.RegionisedWorldData regionisedWorldData = this.getCurrentWorldData(); // Folia - region threading
+            long i = regionisedWorldData.getRedstoneGameTime() + 1L; // Folia - region threading
 
-            this.serverLevelData.setGameTime(i);
-            this.serverLevelData.getScheduledEvents().tick(this.server, i);
-            if (this.levelData.getGameRules().getBoolean(GameRules.RULE_DAYLIGHT)) {
+            regionisedWorldData.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);
             }
 
@@ -830,15 +840,23 @@ 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();
@@ -846,7 +864,7 @@ 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 - disable thunder
             blockposition.set(this.findLightningTargetAround(this.getBlockRandomPos(j, 0, k, 15))); // Paper
@@ -941,7 +959,7 @@ 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;
                     }
@@ -955,7 +973,7 @@ 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)
                 }
@@ -1009,7 +1027,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public boolean isHandlingTick() {
-        return this.handlingTick;
+        return this.getCurrentWorldData().isHandlingTick(); // Folia - regionised ticking
     }
 
     public boolean canSleepThroughNights() {
@@ -1041,6 +1059,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public void updateSleepingPlayerList() {
+        // Folia start - region threading
+        if (!io.papermc.paper.threadedregions.RegionisedServer.isGlobalTickThread()) {
+            io.papermc.paper.threadedregions.RegionisedServer.getInstance().addTask(() -> {
+                ServerLevel.this.updateSleepingPlayerList();
+            });
+            return;
+        }
+        // Folia end - region threading
         if (!this.players.isEmpty() && this.sleepStatus.update(this.players)) {
             this.announceSleepStatus();
         }
@@ -1052,7 +1078,7 @@ 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()) {
@@ -1138,23 +1164,24 @@ 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
@@ -1218,7 +1245,7 @@ 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);
@@ -1251,7 +1278,16 @@ 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
@@ -1274,7 +1310,7 @@ 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
@@ -1291,7 +1327,16 @@ 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();
@@ -1379,7 +1424,15 @@ public class ServerLevel extends Level implements WorldGenLevel {
             // Paper - rewrite chunk system - entity saving moved into ChunkHolder
 
         } else if (close) { chunkproviderserver.close(false); } // Paper - rewrite chunk system
+        // Folia - move into saveLevelData()
+    }
 
+    public void saveLevelData() { // Folia - region threading
+        if (this.dragonFight != null) {
+            this.serverLevelData.setEndDragonFightData(this.dragonFight.saveData()); // CraftBukkit
+        }
+        // Folia start - region threading
+        // moved from save
         // CraftBukkit start - moved from MinecraftServer.saveChunks
         ServerLevel worldserver1 = this;
 
@@ -1387,12 +1440,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
         this.serverLevelData.setCustomBossEvents(this.server.getCustomBossEvents().save());
         this.convertable.saveDataTag(this.server.registryAccess(), this.serverLevelData, this.server.getPlayerList().getSingleplayerData());
         // CraftBukkit end
-    }
-
-    private void saveLevelData() {
-        if (this.dragonFight != null) {
-            this.serverLevelData.setEndDragonFightData(this.dragonFight.saveData()); // CraftBukkit
-        }
+        // Folia end - region threading
 
         this.getChunkSource().getDataStorage().save();
     }
@@ -1447,6 +1495,19 @@ 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);
@@ -1548,8 +1609,8 @@ 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
@@ -1688,7 +1749,7 @@ 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"));
@@ -1701,7 +1762,7 @@ 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
@@ -1724,7 +1785,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
             }
 
             try {
-                this.isUpdatingNavigations = true;
+                //this.isUpdatingNavigations = true; // Folia - region threading
                 iterator = list.iterator();
 
                 while (iterator.hasNext()) {
@@ -1733,7 +1794,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     navigationabstract1.recomputePath();
                 }
             } finally {
-                this.isUpdatingNavigations = false;
+                //this.isUpdatingNavigations = false; // Folia - region threading
             }
 
         }
@@ -1742,23 +1803,23 @@ 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
@@ -1784,7 +1845,7 @@ 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();
@@ -1799,25 +1860,28 @@ 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.RegionisedWorldData 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) {
@@ -1828,12 +1892,12 @@ 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
@@ -1857,7 +1921,7 @@ 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 Expansion
-        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, ServerPlayer sender, T t0, double d0, double d1, double d2, int i, double d3, double d4, double d5, double d6, boolean force) {
         // Paper end
@@ -1910,7 +1974,14 @@ 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
@@ -1918,6 +1989,61 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return (Entity) this.getEntities().get(uuid);
     }
 
+    // Folia start - region threading
+    private final java.util.concurrent.atomic.AtomicLong nonFullSyncLoadIdGenerator = new java.util.concurrent.atomic.AtomicLong();
+
+    private ChunkAccess getIfAboveStatus(int chunkX, int chunkZ, net.minecraft.world.level.chunk.ChunkStatus status) {
+        io.papermc.paper.chunk.system.scheduling.NewChunkHolder loaded =
+            this.chunkTaskScheduler.chunkHolderManager.getChunkHolder(chunkX, chunkZ);
+        io.papermc.paper.chunk.system.scheduling.NewChunkHolder.ChunkCompletion loadedCompletion;
+        if (loaded != null && (loadedCompletion = loaded.getLastChunkCompletion()) != null && loadedCompletion.genStatus().isOrAfter(status)) {
+            return loadedCompletion.chunk();
+        }
+
+        return null;
+    }
+
+    @Override
+    public ChunkAccess syncLoadNonFull(int chunkX, int chunkZ, net.minecraft.world.level.chunk.ChunkStatus status) {
+        if (status == null || status.isOrAfter(net.minecraft.world.level.chunk.ChunkStatus.FULL)) {
+            throw new IllegalArgumentException("Status: " + status.getName());
+        }
+        ChunkAccess loaded = this.getIfAboveStatus(chunkX, chunkZ, status);
+        if (loaded != null) {
+            return loaded;
+        }
+
+        Long ticketId = Long.valueOf(this.nonFullSyncLoadIdGenerator.getAndIncrement());
+        int ticketLevel = 33 + net.minecraft.world.level.chunk.ChunkStatus.getDistance(status);
+        this.chunkTaskScheduler.chunkHolderManager.addTicketAtLevel(
+            TicketType.NON_FULL_SYNC_LOAD, chunkX, chunkZ, ticketLevel, ticketId
+        );
+        this.chunkTaskScheduler.chunkHolderManager.processTicketUpdates();
+
+        this.chunkTaskScheduler.beginChunkLoadForNonFullSync(chunkX, chunkZ, status, ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.BLOCKING);
+
+        // we could do a simple spinwait here, since we do not need to process tasks while performing this load
+        // but we process tasks only because it's a better use of the time spent
+        this.chunkSource.mainThreadProcessor.managedBlock(() -> {
+            return ServerLevel.this.getIfAboveStatus(chunkX, chunkZ, status) != null;
+        });
+
+        loaded = ServerLevel.this.getIfAboveStatus(chunkX, chunkZ, status);
+        if (loaded == null) {
+            throw new IllegalStateException("Expected chunk to be loaded for status " + status);
+        }
+
+        // let the next process ticket updates call pick this up
+        this.chunkTaskScheduler.chunkHolderManager.pushDelayedTicketUpdate(
+            io.papermc.paper.chunk.system.scheduling.ChunkHolderManager.TicketOperation.removeOp(
+                chunkX, chunkZ, TicketType.NON_FULL_SYNC_LOAD, ticketLevel, ticketId
+            )
+        );
+
+        return loaded;
+    }
+    // Folia end - region threading
+
     @Nullable
     public BlockPos findNearestMapStructure(TagKey<Structure> structureTag, BlockPos pos, int radius, boolean skipReferencedStructures) {
         if (!this.serverLevelData.worldGenOptions().generateStructures()) { // CraftBukkit
@@ -2082,7 +2208,7 @@ 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);
@@ -2110,13 +2236,18 @@ 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.RegionisedServer.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
                     if (optional.isEmpty() && this.getPoiManager().exists(blockposition1, poiType -> true)) {
                         this.getPoiManager().remove(blockposition1);
@@ -2124,7 +2255,12 @@ public class ServerLevel extends Level implements WorldGenLevel {
                     // Paper end
                     this.getPoiManager().add(blockposition1, holder);
                     DebugPackets.sendPoiAddedPacket(this, blockposition1);
-                });
+                }; // Folia - region threading
+                // Folia start - region threading
+                io.papermc.paper.threadedregions.RegionisedServer.getInstance().taskQueue.queueChunkTask(
+                    this, blockposition1.getX() >> 4, blockposition1.getZ() >> 4, run
+                );
+                // Folia end - region threading
             });
         }
     }
@@ -2171,7 +2307,7 @@ 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) {
@@ -2185,7 +2321,7 @@ 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");
@@ -2331,7 +2467,7 @@ 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();
@@ -2344,7 +2480,7 @@ 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());
         });
     }
@@ -2353,7 +2489,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     public void blockUpdated(BlockPos pos, Block block) {
         if (!this.isDebug()) {
             // CraftBukkit start
-            if (populating) {
+            if (this.getCurrentWorldData().populating) { // Folia - region threading
                 return;
             }
             // CraftBukkit end
@@ -2396,9 +2532,7 @@ 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) {
@@ -2431,6 +2565,12 @@ 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();
@@ -2443,11 +2583,7 @@ 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
@@ -2468,13 +2604,14 @@ 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
@@ -2496,7 +2633,7 @@ 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
@@ -2544,16 +2681,16 @@ 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) return; // Paper - Don't tick markers
-            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;
@@ -2581,7 +2718,7 @@ 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) {
@@ -2592,7 +2729,9 @@ 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
                 }
             }
 
@@ -2666,7 +2805,7 @@ 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) {
@@ -2677,13 +2816,16 @@ 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 869daafbc236b3ff63f878e5fe28427fde75afe5..ecd5b4542f95717e830fe3d845e79090aa341c2b 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -181,7 +181,7 @@ import org.bukkit.inventory.MainHand;
 public class ServerPlayer extends Player {
 
     private static final Logger LOGGER = LogUtils.getLogger();
-    public long lastSave = MinecraftServer.currentTick; // Paper
+    public long lastSave = Long.MIN_VALUE; // Paper // Folia - threaded regions
     private static final int NEUTRAL_MOB_DEATH_NOTIFICATION_RADII_XZ = 32;
     private static final int NEUTRAL_MOB_DEATH_NOTIFICATION_RADII_Y = 10;
     public ServerGamePacketListenerImpl connection;
@@ -242,11 +242,7 @@ public class ServerPlayer extends Player {
     public boolean queueHealthUpdatePacket = false;
     public net.minecraft.network.protocol.game.ClientboundSetHealthPacket queuedHealthUpdatePacket;
     // Paper end
-    // Paper start - mob spawning rework
-    public static final int MOBCATEGORY_TOTAL_ENUMS = net.minecraft.world.entity.MobCategory.values().length;
-    public final int[] mobCounts = new int[MOBCATEGORY_TOTAL_ENUMS]; // Paper
-    public final com.destroystokyo.paper.util.PooledHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> cachedSingleMobDistanceMap;
-    // Paper end
+    // Folia - region threading - revert per player mob caps
 
     // CraftBukkit start
     public String displayName;
@@ -311,6 +307,9 @@ public class ServerPlayer extends Player {
         });
     }
 
+    // Folia start - region threading
+    // Folia end - region threading
+
     public ServerPlayer(MinecraftServer server, ServerLevel world, GameProfile profile) {
         super(world, world.getSharedSpawnPos(), world.getSharedSpawnAngle(), profile);
         this.chatVisibility = ChatVisiblity.FULL;
@@ -408,7 +407,7 @@ public class ServerPlayer extends Player {
         this.adventure$displayName = net.kyori.adventure.text.Component.text(this.getScoreboardName()); // Paper
         this.bukkitPickUpLoot = true;
         this.maxHealthCache = this.getMaxHealth();
-        this.cachedSingleMobDistanceMap = new com.destroystokyo.paper.util.PooledHashSets.PooledObjectLinkedOpenHashSet<>(this); // Paper
+        // Folia - region threading - revert per player mob caps
     }
 
     // Yes, this doesn't match Vanilla, but it's the best we can do for now.
@@ -450,11 +449,11 @@ public class ServerPlayer extends Player {
     }
     // CraftBukkit end
 
-    public void fudgeSpawnLocation(ServerLevel world) {
-        BlockPos blockposition = world.getSharedSpawnPos();
+    public static void fudgeSpawnLocation(ServerLevel world, ServerPlayer player, ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) { // Folia - region threading
+        BlockPos blockposition = world.getSharedSpawnPos(); final BlockPos spawnPos = blockposition; // Folia - region threading
 
         if (world.dimensionType().hasSkyLight() && world.serverLevelData.getGameType() != GameType.ADVENTURE) { // CraftBukkit
-            int i = Math.max(0, this.server.getSpawnRadius(world));
+            int i = Math.max(0, MinecraftServer.getServer().getSpawnRadius(world)); // Folia - region threading
             int j = Mth.floor(world.getWorldBorder().getDistanceToBorder((double) blockposition.getX(), (double) blockposition.getZ()));
 
             if (j < i) {
@@ -468,33 +467,76 @@ public class ServerPlayer extends Player {
             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 j1 = getCoprime(i1); // Folia - region threading
             int k1 = RandomSource.create().nextInt(i1);
 
-            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);
-
-                if (blockposition1 != null) {
-                    this.moveTo(blockposition1, 0.0F, 0.0F);
-                    if (world.noCollision(this, this.getBoundingBox(), true)) { // Paper - make sure this loads chunks, we default to NOT loading now
-                        break;
-                    }
+            // Folia start - region threading
+            int[] l1 = new int[1];
+            final int finalI = i;
+            Runnable attempt = new Runnable() {
+                @Override
+                public void run() {
+                    int i2 = (k1 + j1 * l1[0]) % i1;
+                    int j2 = i2 % (finalI * 2 + 1);
+                    int k2 = i2 / (finalI * 2 + 1);
+                    int x = blockposition.getX() + j2 - finalI;
+                    int z = blockposition.getZ() + k2 - finalI;
+
+                    world.loadChunksForMoveAsync(player.getBoundingBoxAt(x + 0.5, 0, z + 0.5),
+                        ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                        (c) -> {
+                            BlockPos blockposition1 = PlayerRespawnLogic.getOverworldRespawnPos(world, x, z);
+                            if (blockposition1 != null) {
+                                AABB aabb = player.getBoundingBoxAt(blockposition1.getX() + 0.5, blockposition1.getY(), blockposition1.getZ() + 0.5);
+                                if (world.noCollision(player, aabb, true)) { // Paper - make sure this loads chunks, we default to NOT loading now
+                                    toComplete.complete(io.papermc.paper.util.MCUtil.toLocation(world, Vec3.atBottomCenterOf(blockposition1), world.levelData.getSpawnAngle(), 0.0f));
+                                    return;
+                                }
+                            }
+                            if (++l1[0] >= i1) {
+                                LOGGER.warn("Found no spawn in radius for player " + player.getName() + ", selecting set spawn point " + spawnPos + " in world '" + world.getWorld().getKey() + "'");
+                                // if we return null, then no chunks may be loaded. but this call requires to return a location with
+                                // loaded chunks, so we need to return something (vanilla does not do this logic, it assumes
+                                // something is returned always)
+                                // we can just return the set spawn position
+                                world.loadChunksForMoveAsync(player.getBoundingBoxAt(spawnPos.getX() + 0.5, spawnPos.getY(), spawnPos.getZ() + 0.5),
+                                    ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                                    (c0) -> {
+                                        toComplete.complete(io.papermc.paper.util.MCUtil.toLocation(world, Vec3.atBottomCenterOf(spawnPos), world.levelData.getSpawnAngle(), 0.0f));
+                                    }
+                                );
+                                return;
+                            } else {
+                                this.run();
+                            }
+                        }
+                     );
                 }
-            }
+            };
+            attempt.run();
+            // Folia end - region threading
         } else {
-            this.moveTo(blockposition, 0.0F, 0.0F);
-
-            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());
-            }
+            // 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;
     }
 
@@ -1147,6 +1189,338 @@ 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.getLevel().noCollision(this, this.getBoundingBox(), true) && this.getY() < (double)this.getLevel().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.isVehicle() || this.isPassenger()) {
+            throw new IllegalStateException("Dead player should not be a vehicle or passenger");
+        }
+
+        ServerLevel origin = this.getLevel();
+        ServerLevel respawnWorld = this.server.getLevel(this.getRespawnDimension());
+
+        // modified based off PlayerList#respawn
+
+        EntityTreeNode passengerTree = this.makePassengerTree();
+
+        this.isChangingDimension = true;
+        // must be manually removed from connections
+        this.getLevel().getCurrentWorldData().connections.remove(this.connection.connection);
+        origin.removePlayerImmediately(this, RemovalReason.CHANGED_DIMENSION);
+
+        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) -> {
+            // reset player if needed
+            if (!alive) {
+                ServerPlayer.this.reset();
+            }
+
+            // 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.getLevel().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.isPassenger());
+        this.connection.resetPosition();
+    }
+
+    @Override
+    protected ServerPlayer transformForAsyncTeleport(ServerLevel destination, Vec3 pos, Float yaw, Float pitch, Vec3 speedDirectionUpdate) {
+        // must be manually removed from connections
+        this.getLevel().getCurrentWorldData().connections.remove(this.connection.connection);
+        this.getLevel().removePlayerImmediately(this, Entity.RemovalReason.CHANGED_DIMENSION);
+
+        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.getLevel().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(), treeNode.parent == null
+            );
+            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(
+                    destination.dimensionTypeId(), destination.dimension(),
+                    BiomeManager.obfuscateSeed(destination.getSeed()),
+                    this.gameMode.getGameModeForPlayer(),
+                    this.gameMode.getPreviousGameModeForPlayer(),
+                    destination.isDebug(), destination.isFlat(),
+                    // if we do not want to respawn, we aren't dead
+                    (teleportFlags & TELEPORT_FLAGS_PLAYER_RESPAWN) == 0L ? (byte)1 : (byte)0,
+                    this.getLastDeathLocation()
+                )
+            );
+            // 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.getLevel().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(), treeNode.parent == null
+            );
+            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.getLevel().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) {
@@ -2098,6 +2472,12 @@ public class ServerPlayer extends Player {
 
         if (entity1 == entity) return; // new spec target is the current spec target
 
+        // Folia start - region threading
+        if (!io.papermc.paper.util.TickThread.isTickThreadFor(entity)) {
+            return;
+        }
+        // Folia end - region threading
+
         if (entity == this) {
             com.destroystokyo.paper.event.player.PlayerStopSpectatingEntityEvent playerStopSpectatingEntityEvent = new com.destroystokyo.paper.event.player.PlayerStopSpectatingEntityEvent(this.getBukkitEntity(), entity1.getBukkitEntity());
 
@@ -2132,7 +2512,7 @@ public class ServerPlayer extends Player {
             this.getBukkitEntity().teleport(new Location(entity.getCommandSenderWorld().getWorld(), entity.getX(), entity.getY(), entity.getZ(), this.getYRot(), this.getXRot()), TeleportCause.SPECTATE); // Correctly handle cross-world entities from api calls by using CB teleport
 
             // Make sure we're tracking the entity before sending
-            ChunkMap.TrackedEntity tracker = ((ServerLevel)entity.level).getChunkSource().chunkMap.entityMap.get(entity.getId());
+            ChunkMap.TrackedEntity tracker = entity.tracker; // Folia - region threading
             if (tracker != null) { // dumb plugins...
                 tracker.updatePlayer(this);
             }
@@ -2567,7 +2947,7 @@ 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 58b093bb1de78ee3b3b2ea364aa50474883f443a..147c9baaf73d0f8c315477ee32236bc163e1736c 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
@@ -123,7 +123,7 @@ public class ServerPlayerGameMode {
     }
 
     public void tick() {
-        this.gameTicks = MinecraftServer.currentTick; // CraftBukkit;
+        ++this.gameTicks; // CraftBukkit; // Folia - region threading
         BlockState iblockdata;
 
         if (this.hasDelayedDestroy) {
@@ -408,7 +408,7 @@ public class ServerPlayerGameMode {
             } else {
                 // CraftBukkit start
                 org.bukkit.block.BlockState state = bblock.getState();
-                level.captureDrops = new ArrayList<>();
+                level.getCurrentWorldData().captureDrops = new ArrayList<>(); // Folia - region threading
                 // CraftBukkit end
                 block.playerWillDestroy(this.level, pos, iblockdata, this.player);
                 boolean flag = this.level.removeBlock(pos, false);
@@ -436,8 +436,8 @@ public class ServerPlayerGameMode {
                     // return true; // CraftBukkit
                 }
                 // CraftBukkit start
-                java.util.List<net.minecraft.world.entity.item.ItemEntity> itemsToDrop = level.captureDrops; // Paper - store current list
-                level.captureDrops = null; // Paper - Remove this earlier so that we can actually drop stuff
+                java.util.List<net.minecraft.world.entity.item.ItemEntity> itemsToDrop = level.getCurrentWorldData().captureDrops; // Paper - store current list // Folia - region threading
+                level.getCurrentWorldData().captureDrops = null; // Paper - 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 - use stored ref
                 }
diff --git a/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java b/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
index 660693c6dc0ef86f4013df980b6d0c11c03e46cd..eef501b0558680e5563b0a15a93bd3ab217b91d8 100644
--- a/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
+++ b/src/main/java/net/minecraft/server/level/ThreadedLevelLightEngine.java
@@ -98,10 +98,15 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
         this.chunkMap.level.chunkTaskScheduler.lightExecutor.queueRunnable(() -> { // 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, true), 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.RegionisedServer.getInstance().taskQueue.queueChunkTask(
+                    (ServerLevel)this.theLightEngine.getWorld(), chunkPos.x, chunkPos.z, run
+                );
+                // Folia end - region threading
             }, onComplete);
         });
         this.tryScheduleUpdate();
@@ -109,7 +114,7 @@ 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<CompletableFuture<Void>> runnable) {
         final ServerLevel world = (ServerLevel)this.theLightEngine.getWorld();
@@ -128,11 +133,16 @@ 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.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+                world, chunkX, chunkZ, run
+            );
+            // Folia end - region threading
             return;
         }
 
@@ -145,22 +155,28 @@ public class ThreadedLevelLightEngine extends LevelLightEngine implements AutoCl
             return;
         }
 
-        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.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.thenAccept((final Void ignore) -> {
+            io.papermc.paper.threadedregions.RegionisedServer.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 97d1ff2af23bac14e67bca5896843325aaa5bfc1..cf38de369a57e30a29dfa13e116f950b0dbf5904 100644
--- a/src/main/java/net/minecraft/server/level/TicketType.java
+++ b/src/main/java/net/minecraft/server/level/TicketType.java
@@ -35,6 +35,12 @@ public class TicketType<T> {
     public static final TicketType<Long> POI_LOAD = create("poi_load", Long::compareTo);
     public static final TicketType<Unit> UNLOAD_COOLDOWN = create("unload_cooldown", (u1, u2) -> 0, 5 * 20);
     // 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> NON_FULL_SYNC_LOAD = create("non_full_sync_load", Long::compareTo);
+    // 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 877498729c66de9aa6a27c9148f7494d7895615c..d8af2d59fb1f112f2f1a9fdbb3517fc72a2e572d 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/ServerConnectionListener.java b/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
index abcc3266d18f34d160eac87fdea153dce24c60b8..7cf0619883577a0f21ed75ba70ece90d5c316c21 100644
--- a/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
+++ b/src/main/java/net/minecraft/server/network/ServerConnectionListener.java
@@ -155,10 +155,13 @@ public class ServerConnectionListener {
                     // Paper end
 
                     // ServerConnectionListener.this.connections.add((Connection) object); // CraftBukkit - decompile error
-                    pending.add((Connection) object); // Paper
+                    // Folia - connection fixes - move down
                     channel.pipeline().addLast("packet_handler", (ChannelHandler) object);
                     ((Connection) object).setListener(new ServerHandshakePacketListenerImpl(ServerConnectionListener.this.server, (Connection) object));
                     io.papermc.paper.network.ChannelInitializeListenerHolder.callListeners(channel); // Paper
+                    // Folia start - regionised threading
+                    io.papermc.paper.threadedregions.RegionisedServer.getInstance().addConnection((Connection)object);
+                    // Folia end - regionised threading
                 }
             }).group((EventLoopGroup) lazyinitvar.get()).localAddress(address)).option(ChannelOption.AUTO_READ, false).bind().syncUninterruptibly()); // CraftBukkit // Paper
         }
@@ -217,7 +220,7 @@ public class ServerConnectionListener {
             // Spigot Start
             this.addPending(); // Paper
             // 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 3472f7f9b98d6d9c9f6465872803ef17fa67486d..e8e2d8e481ff798dc73bfdfe956cd7d9cabe4403 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -320,10 +320,10 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
 
     private final org.bukkit.craftbukkit.CraftServer cserver;
     public boolean processedDisconnect;
-    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;
 
     // Get position of last block hit for BlockDamageLevel.STOPPED
@@ -340,8 +340,40 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
     }
     // 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());
+
+    private void checkKeepAlive() {
+        long currentTime = Util.getMillis();
+        long elapsedTime = currentTime - this.keepAliveTime;
+
+        if (this.keepAlivePending) {
+            if (!this.processedDisconnect && elapsedTime >= KEEPALIVE_LIMIT) { // check keepalive limit, don't fire if already disconnected
+                ServerGamePacketListenerImpl.LOGGER.warn("{} was kicked due to keepalive timeout!", this.player.getScoreboardName()); // more info
+                this.disconnect(Component.translatable("disconnect.timeout", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.TIMEOUT); // Paper - kick event cause
+            }
+        } else {
+            if (elapsedTime >= 15000L) { // 15 seconds
+                this.keepAlivePending = true;
+                this.keepAliveTime = currentTime;
+                this.keepAliveChallenge = currentTime;
+                this.send(new ClientboundKeepAlivePacket(this.keepAliveChallenge));
+            }
+        }
+    }
+    // Folia end - region threading
+
     @Override
     public void tick() {
+        // Folia start - region threading
+        this.checkKeepAlive();
+        if (this.player.wonGame) {
+            return;
+        }
+        // Folia end - region threading
         if (this.ackBlockChangesUpTo > -1) {
             this.send(new ClientboundBlockChangedAckPacket(this.ackBlockChangesUpTo));
             this.ackBlockChangesUpTo = -1;
@@ -393,22 +425,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         this.server.getProfiler().push("keepAlive");
         // Paper Start - give clients a longer time to respond to pings as per pre 1.12.2 timings
         // This should effectively place the keepalive handling back to "as it was" before 1.12.2
-        long currentTime = Util.getMillis();
-        long elapsedTime = currentTime - this.keepAliveTime;
-
-        if (this.keepAlivePending) {
-            if (!this.processedDisconnect && elapsedTime >= KEEPALIVE_LIMIT) { // check keepalive limit, don't fire if already disconnected
-                ServerGamePacketListenerImpl.LOGGER.warn("{} was kicked due to keepalive timeout!", this.player.getScoreboardName()); // more info
-                this.disconnect(Component.translatable("disconnect.timeout", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.TIMEOUT); // Paper - kick event cause
-            }
-        } else {
-            if (elapsedTime >= 15000L) { // 15 seconds
-                this.keepAlivePending = true;
-                this.keepAliveTime = currentTime;
-                this.keepAliveChallenge = currentTime;
-                this.send(new ClientboundKeepAlivePacket(this.keepAliveChallenge));
-            }
-        }
+        // Folia - region threading - move to own method above
         // Paper end
 
         this.server.getProfiler().pop();
@@ -441,6 +458,19 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         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
@@ -477,24 +507,8 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         if (this.processedDisconnect) {
             return;
         }
-        if (!this.cserver.isPrimaryThread()) {
-            Waitable waitable = new Waitable() {
-                @Override
-                protected Object evaluate() {
-                    ServerGamePacketListenerImpl.this.disconnect(reason, cause); // Paper - adventure, kick event cause
-                    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(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;
         }
 
@@ -525,7 +539,6 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
 
         Objects.requireNonNull(this.connection);
         // CraftBukkit - Don't wait
-        minecraftserver.scheduleOnMain(networkmanager::handleDisconnection); // Paper
     }
 
     private <T, R> CompletableFuture<R> filterTextPacket(T text, BiFunction<TextFilter, T, CompletableFuture<R>> filterer) {
@@ -608,9 +621,10 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                 // 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;
@@ -864,13 +878,13 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         // PacketUtils.ensureRunningOnSameThread(packet, this, this.player.getLevel()); // Paper - 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 start - split and make configurable
-            server.scheduleOnMain(() -> this.disconnect(Component.translatable("disconnect.spam", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM)); // Paper - kick event cause
+            this.disconnect(Component.translatable("disconnect.spam", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Paper - kick event cause // Folia - region threading
             return;
         }
         // Paper start
         String str = packet.getCommand(); int index = -1;
         if (str.length() > 64 && ((index = str.indexOf(' ')) == -1 || index >= 64)) {
-            server.scheduleOnMain(() -> this.disconnect(Component.translatable("disconnect.spam", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM)); // Paper - kick event cause
+            this.disconnect(Component.translatable("disconnect.spam", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Paper - kick event cause // Folia - region threading
             return;
         }
         // Paper end
@@ -895,7 +909,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
             if (!event.isHandled()) {
                 if (!event.isCancelled()) {
 
-                    this.server.scheduleOnMain(() -> { // This needs to be on main
+                    this.player.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
                         ParseResults<CommandSourceStack> parseresults = this.server.getCommands().getDispatcher().parse(stringreader, this.player.createCommandSourceStack());
 
                         this.server.getCommands().getDispatcher().getCompletionSuggestions(parseresults).thenAccept((suggestions) -> {
@@ -906,7 +920,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                             this.connection.send(new ClientboundCommandSuggestionsPacket(packet.getId(), suggestEvent.getSuggestions()));
                             // Paper end - Brigadier API
                         });
-                    });
+                    }, null, 1L); // Folia - region threading
                 }
             } else if (!completions.isEmpty()) {
                 final com.mojang.brigadier.suggestion.SuggestionsBuilder builder0 = new com.mojang.brigadier.suggestion.SuggestionsBuilder(command, stringreader.getTotalLength());
@@ -1215,7 +1229,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                 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;
@@ -1238,17 +1252,17 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
 
             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
         // 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();
 
@@ -1435,9 +1449,10 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                             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);
@@ -1829,9 +1844,9 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                 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.RegionisedServer.getCurrentTick()) {
                         this.dropCount = 0;
-                        this.lastDropTick = MinecraftServer.currentTick;
+                        this.lastDropTick = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick();
                     } else {
                         // Else we increment the drop count and check the amount.
                         this.dropCount++;
@@ -2056,7 +2071,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                 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;
                 }
             }
@@ -2117,6 +2132,8 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         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
+        this.disconnectPos = this.player.chunkPosition(); // Folia - region threading - note: only set after removing, since it can tick the player
+        this.player.getLevel().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
@@ -2201,9 +2218,9 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         }
         // CraftBukkit end
         if (ServerGamePacketListenerImpl.isChatMessageIllegal(packet.message())) {
-            this.server.scheduleOnMain(() -> { // Paper - push to main for event firing
+            // Folia - region threading
             this.disconnect(Component.translatable("multiplayer.disconnect.illegal_characters"), org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_CHARACTERS); // Paper - add cause
-            }); // Paper - push to main for event firing
+            // Folia - region threading
         } else {
             Optional<LastSeenMessages> optional = this.tryHandleChat(packet.message(), packet.timeStamp(), packet.lastSeenMessages());
 
@@ -2237,17 +2254,17 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
     @Override
     public void handleChatCommand(ServerboundChatCommandPacket packet) {
         if (ServerGamePacketListenerImpl.isChatMessageIllegal(packet.command())) {
-            this.server.scheduleOnMain(() -> { // Paper - push to main for event firing
+            // Folia - region threading
             this.disconnect(Component.translatable("multiplayer.disconnect.illegal_characters"), org.bukkit.event.player.PlayerKickEvent.Cause.ILLEGAL_CHARACTERS); // Paper
-            }); // Paper - push to main for event firing
+            // Folia - region threading
         } else {
             Optional<LastSeenMessages> optional = this.tryHandleChat(packet.command(), packet.timeStamp(), packet.lastSeenMessages());
 
             if (optional.isPresent()) {
-                this.server.submit(() -> {
+                this.player.getBukkitEntity().taskScheduler.schedule((ServerPlayer player) -> { // Folia - region threading
                     this.performChatCommand(packet, (LastSeenMessages) optional.get());
                     this.detectRateSpam("/" + packet.command()); // Spigot
-                });
+                }, null, 1L); // Folia - region threading
             }
 
         }
@@ -2321,9 +2338,9 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
     private Optional<LastSeenMessages> tryHandleChat(String message, Instant timestamp, LastSeenMessages.Update acknowledgment) {
         if (!this.updateChatOrder(timestamp)) {
             ServerGamePacketListenerImpl.LOGGER.warn("{} sent out-of-order chat: '{}': {} > {}", this.player.getName().getString(), message, this.lastChatTimeStamp.get().getEpochSecond(), timestamp.getEpochSecond()); // Paper
-            this.server.scheduleOnMain(() -> { // Paper - push to main
+            // Folia - region threading
             this.disconnect(Component.translatable("multiplayer.disconnect.out_of_order_chat"), org.bukkit.event.player.PlayerKickEvent.Cause.OUT_OF_ORDER_CHAT); // Paper - kick event ca
-            }); // Paper - push to main
+            // Folia - region threading
             return Optional.empty();
         } else if (this.player.isRemoved() || this.player.getChatVisibility() == ChatVisiblity.HIDDEN) { // CraftBukkit - dead men tell no tales
             this.send(new ClientboundSystemChatPacket(Component.translatable("chat.disabled.options").withStyle(ChatFormatting.RED), false));
@@ -2396,7 +2413,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
             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());
@@ -2474,6 +2491,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
     public void handleCommand(String s) { // Paper - private -> public
         // Paper Start
         if (!org.spigotmc.AsyncCatcher.shuttingDown && !org.bukkit.Bukkit.isPrimaryThread()) {
+            if (true) throw new UnsupportedOperationException(); // Folia - region threading
             LOGGER.error("Command Dispatched Async: " + s);
             LOGGER.error("Please notify author of plugin causing this execution to fix this bug! see: http://bit.ly/1oSiM6C", new Throwable());
             Waitable<Void> wait = new Waitable<>() {
@@ -2534,6 +2552,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         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
@@ -2889,6 +2908,12 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         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, org.bukkit.event.player.PlayerRespawnEvent.RespawnFlag.END_PORTAL); // Paper - add isEndCreditsRespawn argument
                     CriteriaTriggers.CHANGED_DIMENSION.trigger(this.player, Level.END, Level.OVERWORLD);
@@ -2897,6 +2922,18 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                         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.getLevel().getGameRules().getRule(GameRules.RULE_SPECTATORSGENERATECHUNKS)).set(false, player.getLevel()); // Paper
+                            }
+                        });
+                        return;
+                    }
+                    // Folia end - region threading
+
                     this.player = this.server.getPlayerList().respawn(this.player, false);
                     if (this.server.isHardcore()) {
                         this.player.setGameMode(GameType.SPECTATOR, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.HARDCORE_DEATH, null); // Paper
@@ -3249,7 +3286,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         // Paper start
         if (!org.bukkit.Bukkit.isPrimaryThread()) {
             if (recipeSpamPackets.addAndGet(io.papermc.paper.configuration.GlobalConfiguration.get().spamLimiter.recipeSpamIncrement) > io.papermc.paper.configuration.GlobalConfiguration.get().spamLimiter.recipeSpamLimit) {
-                server.scheduleOnMain(() -> this.disconnect(net.minecraft.network.chat.Component.translatable("disconnect.spam", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM)); // Paper - kick event cause
+                this.disconnect(net.minecraft.network.chat.Component.translatable("disconnect.spam", new Object[0]), org.bukkit.event.player.PlayerKickEvent.Cause.SPAM); // Paper - kick event cause // Folia - region threading
                 return;
             }
         }
@@ -3391,7 +3428,13 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
 
         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);
+        });
     }
 
     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 a25306fe8a35bb70a490e6a0c01d0340bbc0d781..805557d4fedd234a593ccf2655399a2b87ee6b60 100644
--- a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
@@ -53,7 +53,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
     private final byte[] challenge;
     final MinecraftServer server;
     public final Connection connection;
-    public ServerLoginPacketListenerImpl.State state;
+    public volatile ServerLoginPacketListenerImpl.State state; // Folia - region threading
     private int tick;
     public @Nullable
     GameProfile gameProfile;
@@ -80,20 +80,14 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
         }
         // Paper end
         if (this.state == ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT) {
-            // Paper start - prevent logins to be processed even though disconnect was called
-            if (connection.isConnected()) {
+            // Folia start - region threading - rewrite login process
+            String name = this.gameProfile.getName();
+            UUID uniqueId = UUIDUtil.getOrCreatePlayerUUID(this.gameProfile);
+            if (this.server.getPlayerList().pushPendingJoin(name, uniqueId, this.connection)) {
                 this.handleAcceptedLogin();
             }
-            // Paper end
-        } else if (this.state == ServerLoginPacketListenerImpl.State.DELAY_ACCEPT) {
-            ServerPlayer entityplayer = this.server.getPlayerList().getPlayer(this.gameProfile.getId());
-
-            if (entityplayer == null) {
-                this.state = ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT;
-                this.placeNewPlayer(this.delayedAcceptPlayer);
-                this.delayedAcceptPlayer = null;
-            }
-        }
+            // Folia end - region threading - rewrite login process
+        } // Folia - region threading - remove delayed accept
 
         if (this.tick++ == 600) {
             this.disconnect(Component.translatable("multiplayer.disconnect.slow_login"));
@@ -163,7 +157,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
             // this.disconnect(ichatbasecomponent);
             // CraftBukkit end
         } else {
-            this.state = ServerLoginPacketListenerImpl.State.ACCEPTED;
+            this.state = ServerLoginPacketListenerImpl.State.HANDING_OFF; // Folia - region threading - rewrite login process
             if (this.server.getCompressionThreshold() >= 0 && !this.connection.isMemoryConnection()) {
                 this.connection.send(new ClientboundLoginCompressionPacket(this.server.getCompressionThreshold()), PacketSendListener.thenRun(() -> {
                     this.connection.setupCompression(this.server.getCompressionThreshold(), true);
@@ -171,17 +165,55 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
             }
 
             this.connection.send(new ClientboundGameProfilePacket(this.gameProfile));
-            ServerPlayer entityplayer = this.server.getPlayerList().getPlayer(this.gameProfile.getId());
+            // Folia - region threading - rewrite login process
 
             try {
-                ServerPlayer entityplayer1 = this.server.getPlayerList().getPlayerForLogin(this.gameProfile, s); // CraftBukkit - add player reference
-
-                if (entityplayer != null) {
-                    this.state = ServerLoginPacketListenerImpl.State.DELAY_ACCEPT;
-                    this.delayedAcceptPlayer = entityplayer1;
-                } else {
-                    this.placeNewPlayer(entityplayer1);
-                }
+                // Folia start - region threading - rewrite login process
+                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.fastFloor(loc.getX()) >> 4;
+                    int chunkZ = net.minecraft.util.Mth.fastFloor(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.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+                        world, chunkX, chunkZ,
+                        () -> {
+                            // now at this point the connection is held by the region, so we have to check isConnected()
+                            // this would have been handled in connection ticking, but we are in a state between
+                            // being owned by the global tick thread and the region so we have to do it
+                            if (t != null || !ServerLoginPacketListenerImpl.this.connection.isConnected()) {
+                                ServerLoginPacketListenerImpl.this.connection.handleDisconnection();
+                                return;
+                            }
+                            ServerLoginPacketListenerImpl.this.state = State.ACCEPTED;
+                            ServerLoginPacketListenerImpl.this.server.getPlayerList().placeNewPlayer(
+                                ServerLoginPacketListenerImpl.this.connection,
+                                s,
+                                data.getValue(),
+                                lastKnownName.getValue(),
+                                loc
+                            );
+                        },
+                        ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER
+                    );
+                });
+                this.server.getPlayerList().loadSpawnForNewPlayer(this.connection, s, data, lastKnownName, toComplete);
+                // Folia end - region threading - rewrite login process
             } catch (Exception exception) {
                 ServerLoginPacketListenerImpl.LOGGER.error("Couldn't place player in world", exception);
                 MutableComponent ichatmutablecomponent = Component.translatable("multiplayer.disconnect.invalid_player_data");
@@ -198,9 +230,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
 
     }
 
-    private void placeNewPlayer(ServerPlayer player) {
-        this.server.getPlayerList().placeNewPlayer(this.connection, player);
-    }
+    // Folia end - region threading - rewrite login process
 
     @Override
     public void onDisconnect(Component reason) {
@@ -397,7 +427,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
                         uniqueId = gameProfile.getId();
                         // Paper end
 
-                        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
@@ -480,7 +510,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener,
 
     public static enum State {
 
-        HELLO, KEY, AUTHENTICATING, NEGOTIATING, READY_TO_ACCEPT, DELAY_ACCEPT, ACCEPTED;
+        HELLO, KEY, AUTHENTICATING, NEGOTIATING, READY_TO_ACCEPT, DELAY_ACCEPT, HANDING_OFF, ACCEPTED; // Folia - region threading
 
         private State() {}
     }
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 3c9d08c37a44a60bc70387d8d0dbd0a39ea98a26..a0267f2e110bacd30f33978414fd2aff2dc84ab1 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -138,7 +138,7 @@ public abstract class PlayerList {
     private static final SimpleDateFormat BAN_DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss z");
     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;
@@ -160,9 +160,56 @@ 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 - Team name used for collideRule
 
+    // Folia start - region threading
+    private final Object stateLock = new Object();
+    private final Map<String, Connection> connectionByName = new java.util.HashMap<>();
+    private final Map<UUID, Connection> connectionById = new java.util.HashMap<>();
+
+    public boolean pushPendingJoin(String userName, UUID byId, Connection conn) {
+        userName = userName.toLowerCase(java.util.Locale.ROOT);
+        Connection conflictingName, conflictingId;
+        synchronized (this.stateLock) {
+            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.stateLock) {
+            this.connectionByName.remove(userName, conn);
+            this.connectionById.remove(byId, conn);
+        }
+    }
+
+    private int getTotalConnections() {
+        synchronized (this.stateLock) {
+            return this.connectionById.size();
+        }
+    }
+    // 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
@@ -184,7 +231,7 @@ public abstract class PlayerList {
     }
     abstract public void loadAndSaveFiles(); // Paper - moved from DedicatedPlayerList constructor
 
-    public void placeNewPlayer(Connection connection, ServerPlayer player) {
+    public void loadSpawnForNewPlayer(Connection connection, ServerPlayer player, org.apache.commons.lang3.mutable.MutableObject<CompoundTag> data, org.apache.commons.lang3.mutable.MutableObject<String> lastKnownName, ca.spottedleaf.concurrentutil.completable.Completable<Location> toComplete) {
         player.isRealPlayer = true; // Paper
         player.loginTime = System.currentTimeMillis(); // Paper
         GameProfile gameprofile = player.getGameProfile();
@@ -234,8 +281,28 @@ public abstract class PlayerList {
             worldserver1 = worldserver;
         }
 
-        if (nbttagcompound == null) player.fudgeSpawnLocation(worldserver1); // Paper - only move to spawn on first login, otherwise, stay where you are....
-
+        // Folia start - region threading - rewrite login process
+        if (nbttagcompound == null) ServerPlayer.fudgeSpawnLocation(worldserver1, player, toComplete); // Folia - only move to spawn on first login, otherwise, stay where you are....
+        if (nbttagcompound != null) {
+            worldserver1.loadChunksForMoveAsync(
+                player.getBoundingBox(),
+                ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGHER,
+                (c) -> {
+                    toComplete.complete(io.papermc.paper.util.MCUtil.toLocation(worldserver1, player.position()));
+                }
+            );
+        }
+        data.setValue(nbttagcompound);
+        lastKnownName.setValue(s);
+        return;
+    }
+    // nbttagcomound -> player data
+    // s -> last known name
+    public void placeNewPlayer(Connection connection, ServerPlayer player, CompoundTag nbttagcompound, String s, Location selectedSpawn) {
+        ServerLevel worldserver1 = ((CraftWorld)selectedSpawn.getWorld()).getHandle();
+        player.setPosRaw(selectedSpawn.getX(), selectedSpawn.getY(), selectedSpawn.getZ());
+        player.lastSave = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick();
+        // Folia end - region threading - rewrite login process
         player.setLevel(worldserver1);
         String s1 = "local";
 
@@ -246,7 +313,7 @@ public abstract class PlayerList {
         // 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();
@@ -265,6 +332,7 @@ public abstract class PlayerList {
 
         player.loadGameTypes(nbttagcompound);
         ServerGamePacketListenerImpl playerconnection = new ServerGamePacketListenerImpl(this.server, connection, player);
+        worldserver1.getCurrentWorldData().connections.add(connection); // Folia - region threading - only AFTER updating listener to game
         GameRules gamerules = worldserver1.getGameRules();
         boolean flag = gamerules.getBoolean(GameRules.RULE_DO_IMMEDIATE_RESPAWN);
         boolean flag1 = gamerules.getBoolean(GameRules.RULE_REDUCEDDEBUGINFO);
@@ -282,7 +350,7 @@ 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;
 
@@ -334,8 +402,7 @@ public abstract class PlayerList {
         ClientboundPlayerInfoUpdatePacket packet = ClientboundPlayerInfoUpdatePacket.createPlayerInitializing(List.of(player));
 
         final List<ServerPlayer> onlinePlayers = Lists.newArrayListWithExpectedSize(this.players.size() - 1); // Paper - use single player info update packet
-        for (int i = 0; i < this.players.size(); ++i) {
-            ServerPlayer entityplayer1 = (ServerPlayer) this.players.get(i);
+        for (ServerPlayer entityplayer1 : this.players) { // Folia - region threadingv
 
             if (entityplayer1.getBukkitEntity().canSee(bukkitPlayer)) {
                 entityplayer1.connection.send(packet);
@@ -451,7 +518,7 @@ public abstract class PlayerList {
         // Paper start - Add to collideRule team if needed
         final 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
@@ -542,7 +609,7 @@ public abstract class PlayerList {
 
     protected void save(ServerPlayer player) {
         if (!player.getBukkitEntity().isPersistent()) return; // CraftBukkit
-        player.lastSave = MinecraftServer.currentTick; // Paper
+        player.lastSave = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick(); // Folia - region threading
         this.playerIo.save(player);
         ServerStatsCounter serverstatisticmanager = (ServerStatsCounter) player.getStats(); // CraftBukkit
 
@@ -582,7 +649,7 @@ public abstract class PlayerList {
         // CraftBukkit end
 
         // Paper start - Remove from collideRule team if needed
-        if (this.collideRuleTeamName != null) {
+        if (false && this.collideRuleTeamName != null) { // Folia - region threading
             final Scoreboard scoreBoard = this.server.getLevel(Level.OVERWORLD).getScoreboard();
             final PlayerTeam team = scoreBoard.getPlayersTeam(this.collideRuleTeamName);
             if (entityplayer.getTeam() == team && team != null) {
@@ -622,6 +689,7 @@ public abstract class PlayerList {
 
         entityplayer.unRide();
         worldserver.removePlayerImmediately(entityplayer, Entity.RemovalReason.UNLOADED_WITH_PLAYER);
+        entityplayer.retireScheduler(); // Folia - region threading
         entityplayer.getAdvancements().stopListening();
         this.players.remove(entityplayer);
         this.playersByName.remove(entityplayer.getScoreboardName().toLowerCase(java.util.Locale.ROOT)); // Spigot
@@ -640,8 +708,7 @@ 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);
@@ -666,19 +733,13 @@ 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", new Object[0]), 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
@@ -717,7 +778,7 @@ public abstract class PlayerList {
             event.disallow(PlayerLoginEvent.Result.KICK_BANNED, 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.getTotalConnections() >= 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
             }
         }
@@ -967,10 +1028,10 @@ 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());
@@ -996,18 +1057,17 @@ 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
         }
 
     }
@@ -1051,8 +1111,7 @@ public abstract class PlayerList {
         if (scoreboardteambase == 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() != scoreboardteambase) {
                     entityplayer.sendSystemMessage(message);
@@ -1063,10 +1122,12 @@ 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;
@@ -1085,7 +1146,9 @@ 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
         }
 
     }
@@ -1095,7 +1158,10 @@ 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
+
         }
 
     }
@@ -1156,8 +1222,7 @@ 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())) {
@@ -1187,9 +1252,12 @@ 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);
+        long now = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick(); // 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 >= interval) {
                 this.save(entityplayer);
                 if (interval != -1 && ++numSaved <= io.papermc.paper.configuration.GlobalConfiguration.get().playerAutoSave.maxPerTick()) { break; }
@@ -1309,6 +1377,20 @@ 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 ichatbasecomponent = PaperAdventure.asVanilla(this.server.server.shutdownMessage()); // Paper - Adventure
+            // CraftBukkit end
+
+            player.connection.send(new net.minecraft.network.protocol.game.ClientboundDisconnectPacket(ichatbasecomponent), net.minecraft.network.PacketSendListener.thenRun(() -> {
+                player.connection.disconnect(ichatbasecomponent);
+            }));
+        }
+        if (true) {
+            return;
+        }
+        // Folia end - region threading
         // Paper end
         // CraftBukkit start - disconnect safely
         for (ServerPlayer player : this.players) {
@@ -1318,7 +1400,7 @@ public abstract class PlayerList {
         // CraftBukkit end
 
         // Paper start - Remove collideRule team if it exists
-        if (this.collideRuleTeamName != null) {
+        if (false && this.collideRuleTeamName != null) { // Folia - region threading
             final 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 4fd709a550bf8da1e996894a1ca6b91206c31e9e..e07eddbfbe3fa5e5915580a0f4d753ce54b33248 100644
--- a/src/main/java/net/minecraft/server/players/StoredUserList.java
+++ b/src/main/java/net/minecraft/server/players/StoredUserList.java
@@ -148,6 +148,7 @@ 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
@@ -178,10 +179,12 @@ 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);
 
@@ -226,5 +229,6 @@ 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 4f5f2c25e12ee6d977bc98d9118650cfe91e6c0e..d227b91defc3992f1a003a19264bc3aa29718795 100644
--- a/src/main/java/net/minecraft/util/SortedArraySet.java
+++ b/src/main/java/net/minecraft/util/SortedArraySet.java
@@ -82,7 +82,7 @@ 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;
     }
 
@@ -169,6 +169,40 @@ 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 83ef8cb27db685cceb5c2b7c9674e17b93ba081c..2d87c16420a97b9142d4ea76ceb6013deed22a1f 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();
+                    //t0.discard(); // Folia - region threading
                 }
             }
         }
diff --git a/src/main/java/net/minecraft/world/damagesource/CombatTracker.java b/src/main/java/net/minecraft/world/damagesource/CombatTracker.java
index ba96589aab8be0a90144f73f7779769146c7a37e..08dc87506686434d2e53e748ead9d05c35f470cd 100644
--- a/src/main/java/net/minecraft/world/damagesource/CombatTracker.java
+++ b/src/main/java/net/minecraft/world/damagesource/CombatTracker.java
@@ -34,7 +34,7 @@ public class CombatTracker {
     public void prepareForDamage() {
         this.resetPreparedStatus();
         Optional<BlockPos> optional = this.mob.getLastClimbablePos();
-        if (optional.isPresent()) {
+        if (optional.isPresent() && io.papermc.paper.util.TickThread.isTickThreadFor((net.minecraft.server.level.ServerLevel)this.mob.level, optional.get())) { // Folia - region threading - may sync load the block, which would crash
             BlockState blockState = this.mob.level.getBlockState(optional.get());
             if (!blockState.is(Blocks.LADDER) && !blockState.is(BlockTags.TRAPDOORS)) {
                 if (blockState.is(Blocks.VINE)) {
@@ -85,6 +85,7 @@ public class CombatTracker {
             CombatEntry combatEntry2 = this.entries.get(this.entries.size() - 1);
             Component component = combatEntry2.getAttackerName();
             Entity entity = combatEntry2.getSource().getEntity();
+            if (!io.papermc.paper.util.TickThread.isTickThreadFor(entity)) entity = null; // Folia - region threading - not safe to access other entity data
             Component component4;
             if (combatEntry != null && combatEntry2.getSource() == DamageSource.FALL) {
                 Component component2 = combatEntry.getAttackerName();
@@ -126,6 +127,7 @@ public class CombatTracker {
         float g = 0.0F;
 
         for(CombatEntry combatEntry : this.entries) {
+            if (!io.papermc.paper.util.TickThread.isTickThreadFor(combatEntry.getSource().getEntity())) { continue; } // Folia - region threading - skip entities we do not own
             if (combatEntry.getSource().getEntity() instanceof Player && (player == null || combatEntry.getDamage() > g)) {
                 g = combatEntry.getDamage();
                 player = (Player)combatEntry.getSource().getEntity();
diff --git a/src/main/java/net/minecraft/world/damagesource/EntityDamageSource.java b/src/main/java/net/minecraft/world/damagesource/EntityDamageSource.java
index b53e04854f960682fae94bb2ef5a12e4274fcebf..01469deddce99a736e661ce9bca8e20e88bb6c1e 100644
--- a/src/main/java/net/minecraft/world/damagesource/EntityDamageSource.java
+++ b/src/main/java/net/minecraft/world/damagesource/EntityDamageSource.java
@@ -35,7 +35,7 @@ public class EntityDamageSource extends DamageSource {
     public Component getLocalizedDeathMessage(LivingEntity entity) {
         Entity var4 = this.entity;
         ItemStack var10000;
-        if (var4 instanceof LivingEntity livingEntity) {
+        if (var4 instanceof LivingEntity livingEntity && io.papermc.paper.util.TickThread.isTickThreadFor(livingEntity)) { // Folia - region threading
             var10000 = livingEntity.getMainHandItem();
         } else {
             var10000 = ItemStack.EMPTY;
diff --git a/src/main/java/net/minecraft/world/damagesource/IndirectEntityDamageSource.java b/src/main/java/net/minecraft/world/damagesource/IndirectEntityDamageSource.java
index 6b5fd3e2e19c2d3d694df94f90fce0d310a1a86c..a7a48cf40db1e31ab03e0f42028b617b4f87c8ad 100644
--- a/src/main/java/net/minecraft/world/damagesource/IndirectEntityDamageSource.java
+++ b/src/main/java/net/minecraft/world/damagesource/IndirectEntityDamageSource.java
@@ -34,7 +34,7 @@ public class IndirectEntityDamageSource extends EntityDamageSource {
         Entity entity1 = this.cause;
         ItemStack itemstack;
 
-        if (entity1 instanceof LivingEntity) {
+        if (entity1 instanceof LivingEntity && io.papermc.paper.util.TickThread.isTickThreadFor(entity1)) { // Folia - region threading
             LivingEntity entityliving1 = (LivingEntity) entity1;
 
             itemstack = entityliving1.getMainHandItem();
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 1eaab1f6923e6aa34b643293347348e5cc19af3c..87e20dc4e787e7b875d97b6cdb6b3ce497f795e8 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -165,7 +165,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
     // Paper start
     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
@@ -239,17 +239,29 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
     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 @Nullable Throwable addedToWorldStack; // Paper - entity debug
     public CraftEntity getBukkitEntity() {
         if (this.bukkitEntity == null) {
-            this.bukkitEntity = CraftEntity.getEntity(this.level.getCraftServer(), this);
+            // Folia start - region threading
+            synchronized (this) {
+                if (this.bukkitEntity == null) {
+                    return this.bukkitEntity = CraftEntity.getEntity(this.level.getCraftServer(), this);
+                }
+            }
+            // Folia end - region threading
         }
         return this.bukkitEntity;
     }
 
+    // Folia start - region threading
+    public CraftEntity getBukkitEntityRaw() {
+        return this.bukkitEntity;
+    }
+    // Folia end - region threading
+
     @Override
     public CommandSender getBukkitSender(CommandSourceStack wrapper) {
         return this.getBukkitEntity();
@@ -488,28 +500,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         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 threading
     // Paper end - optimise entity tracking
     // Paper start - make end portalling safe
     public BlockPos portalBlock;
@@ -541,6 +532,25 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         this.teleportTo(worldserver, null);
     }
     // Paper end - make end portalling safe
+    // Folia start
+    private static final java.util.concurrent.ConcurrentHashMap<Class<? extends Entity>, Integer> CLASS_ID_MAP = new java.util.concurrent.ConcurrentHashMap<>();
+    private static final AtomicInteger CLASS_ID_GENERATOR = new AtomicInteger();
+    public final int classId = CLASS_ID_MAP.computeIfAbsent(this.getClass(), (Class<? extends Entity> c) -> {
+        return CLASS_ID_GENERATOR.getAndIncrement();
+    });
+    private static final java.util.concurrent.atomic.AtomicLong REFERENCE_ID_GENERATOR = new java.util.concurrent.atomic.AtomicLong();
+    public final long referenceId = REFERENCE_ID_GENERATOR.getAndIncrement();
+    // Folia 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;
+        }
+    }
+    // Folia end - region ticking
 
     public Entity(EntityType<?> type, Level world) {
         this.id = Entity.ENTITY_COUNTER.incrementAndGet();
@@ -656,6 +666,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
     }
 
     public final void discard() {
+        // Folia start - region threading
+        if (this.isRemoved()) {
+            return;
+        }
+        // Folia end - region threading
         this.remove(Entity.RemovalReason.DISCARDED);
     }
 
@@ -780,6 +795,12 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
     // 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();
@@ -802,7 +823,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         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();
         }
@@ -903,11 +924,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
                 // This will be called every single tick the entity is in lava, so don't throw an event
                 this.setSecondsOnFire(15, false);
             }
-            CraftEventFactory.blockDamage = (this.lastLavaContact) == null ? null : org.bukkit.craftbukkit.block.CraftBlock.at(level, lastLavaContact);
+            CraftEventFactory.blockDamageRT.set((this.lastLavaContact) == null ? null : org.bukkit.craftbukkit.block.CraftBlock.at(level, lastLavaContact)); // Folia - region threading
             if (this.hurt(DamageSource.LAVA, 4.0F)) {
                 this.playSound(SoundEvents.GENERIC_BURN, 0.4F, 2.0F + this.random.nextFloat() * 0.4F);
             }
-            CraftEventFactory.blockDamage = null;
+            CraftEventFactory.blockDamageRT.set(null); // Folia - region threading
             // CraftBukkit end - we also don't throw an event unless the object in lava is living, to save on some event calls
 
         }
@@ -1015,8 +1036,8 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         } 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.RegionisedServer.getCurrentTick() + 20); // Paper
+                this.activatedImmunityTick = Math.max(this.activatedImmunityTick, io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick() + 20);   // Paper
                 movement = this.limitPistonMovement(movement);
                 if (movement.equals(Vec3.ZERO)) {
                     return;
@@ -3071,6 +3092,11 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
     @Nullable
     public Team 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
         return this.level.getScoreboard().getPlayersTeam(this.getScoreboardName());
     }
@@ -3186,9 +3212,9 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         if (this.fireImmune()) {
             return;
         }
-        CraftEventFactory.entityDamage = lightning;
+        CraftEventFactory.entityDamageRT.set(lightning); // Folia - region threading
         if (!this.hurt(DamageSource.LIGHTNING_BOLT, 5.0F)) {
-            CraftEventFactory.entityDamage = null;
+            CraftEventFactory.entityDamageRT.set(null); // Folia - region threading
             return;
         }
         // CraftBukkit end
@@ -3361,6 +3387,662 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
         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() {
+            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, Entity::moveTo);
+                }
+            }
+        }
+    }
+
+    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;
+
+    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();
+
+        Runnable scheduleEntityJoin = () -> {
+            io.papermc.paper.threadedregions.RegionisedServer.getInstance().taskQueue.queueTickTaskQueue(
+                destination,
+                io.papermc.paper.util.CoordinateUtils.getChunkX(pos), io.papermc.paper.util.CoordinateUtils.getChunkZ(pos),
+                () -> {
+                    List<EntityTreeNode> fullTree = passengerTree.getFullTree();
+                    for (EntityTreeNode node : fullTree) {
+                        node.root.placeSingleSync(originWorld, destination, node, teleportFlags);
+                    }
+
+                    // restore passenger tree
+                    passengerTree.restore();
+                    passengerTree.adjustRiders();
+
+                    // 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.isRemoved() && this.isAlive() && (!(this instanceof net.minecraft.world.entity.LivingEntity livingEntity) || !livingEntity.isSleeping());
+    }
+
+    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);
+    }
+
+    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) {
+        Entity copy = this.getType().create(destination);
+        copy.restoreFrom(this);
+        copy.transform(pos, yaw, pitch, speedDirectionUpdate);
+
+        this.removeAfterChangingDimensions();
+
+        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(pos))) {
+            return false;
+        }
+
+        if ((teleportFlags & TELEPORT_FLAG_TELEPORT_PASSENGERS) != 0L) {
+            if (this.isPassenger()) {
+                return false;
+            }
+        } else {
+            if (this.isVehicle() || this.isPassenger()) {
+                return false;
+            }
+        }
+
+        this.getBukkitEntity(); // force bukkit entity to be created before TPing
+        if (!this.canTeleportAsync()) {
+            return false;
+        }
+        for (Entity entity : this.getIndirectPassengers()) {
+            entity.getBukkitEntity(); // force bukkit entity to be created before TPing
+            if (!entity.canTeleportAsync()) {
+                return false;
+            }
+        }
+
+        // TODO any events that can modify go HERE
+
+        // check for same region
+        if (destination == this.getLevel()) {
+            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();
+
+                // 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() {
+
+    }
+
+    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.getLevel().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.getLevel().getTypeKey() == LevelStem.NETHER ? Level.OVERWORLD : Level.NETHER);
+        if (destination == null) {
+            // wat
+            return false;
+        }
+
+        return this.portalToAsync(destination, false, PortalType.NETHER, null);
+    }
+
+    // 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 this.level.getBlockStateIfLoaded(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,
+                    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;
+                        }
+
+                        // no portal found - create one
+                        destination.loadChunksAsync(
+                            targetPos, portalCreateRadius + 32,
+                            ca.spottedleaf.concurrentutil.executor.standard.PrioritisedExecutor.Priority.HIGH,
+                            (chunks2) -> {
+                                // 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;
+        }
+
+        // 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();
+        }
+
+        ca.spottedleaf.concurrentutil.completable.Completable<PortalInfo> portalInfoCompletable
+            = new ca.spottedleaf.concurrentutil.completable.Completable<>();
+
+        portalInfoCompletable.addWaiter((PortalInfo info, Throwable throwable) -> {
+            // 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
@@ -3859,17 +4541,13 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
     // Paper start
     public void startSeenByPlayer(ServerPlayer player) {
-        if (io.papermc.paper.event.player.PlayerTrackEntityEvent.getHandlerList().getRegisteredListeners().length > 0) {
-            new io.papermc.paper.event.player.PlayerTrackEntityEvent(player.getBukkitEntity(), this.getBukkitEntity()).callEvent();
-        }
+        // Folia - region threading - no
     }
     // Paper end
 
     // Paper start
     public void stopSeenByPlayer(ServerPlayer player) {
-        if(io.papermc.paper.event.player.PlayerUntrackEntityEvent.getHandlerList().getRegisteredListeners().length > 0) {
-            new io.papermc.paper.event.player.PlayerUntrackEntityEvent(player.getBukkitEntity(), this.getBukkitEntity()).callEvent();
-        }
+        // Folia - region threading - no
     }
     // Paper end
 
@@ -4341,7 +5019,8 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
             }
         }
         // 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
@@ -4362,7 +5041,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
         // Paper start - never allow AABB to become desynced from position
         // 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
@@ -4461,7 +5140,23 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
 
         if (reason != RemovalReason.UNLOADED_TO_CHUNK) this.getPassengers().forEach(Entity::stopRiding); // Paper - chunk system - don't adjust passenger state when unloading, it's just not safe (and messes with our logic in entity chunk unload)
         this.levelCallback.onRemove(reason);
+        // Folia start - region threading
+        if (!(this instanceof ServerPlayer) && reason != RemovalReason.CHANGED_DIMENSION) {
+            // Players need to be special cased, because they are regularly removed from the world
+            this.retireScheduler();
+        }
+        // Folia end - region threading
+    }
+
+    // Folia start - region threading
+    /**
+     * Invoked only when the entity is truly removed from the server, never to be added to any world.
+     */
+    public final void retireScheduler() {
+        // we need to force create the bukkit entity so that the scheduler can be retired...
+        this.getBukkitEntity().taskScheduler.retire();
     }
+    // Folia end - region threading
 
     public void unsetRemoved() {
         this.removalReason = null;
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 42eb78830855d7282b7f3f1bdbe85e632d489784..1e36d889edb6b68d52eae9eee3c13802496af864 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -469,7 +469,7 @@ public abstract class LivingEntity extends Entity {
 
         if (this.isDeadOrDying() && this.level.shouldTickDeath(this)) {
             this.tickDeath();
-        }
+        } else { this.broadcastedDeath = false; } // Folia - region threading
 
         if (this.lastHurtByPlayerTime > 0) {
             --this.lastHurtByPlayerTime;
@@ -620,11 +620,14 @@ public abstract class LivingEntity extends Entity {
         return false;
     }
 
+    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.broadcastedDeath = true; // Folia - region threading
             this.level.broadcastEntityEvent(this, (byte) 60);
-            this.remove(Entity.RemovalReason.KILLED);
+            if (!(this instanceof ServerPlayer)) this.remove(Entity.RemovalReason.KILLED); // 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
         }
 
     }
@@ -841,9 +844,9 @@ public abstract class LivingEntity extends Entity {
         }
 
         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 (!level.paperConfig().scoreboards.allowNonPlayerEntitiesOnScoreboards && !(this instanceof net.minecraft.world.entity.player.Player)) { scoreboardteam = null; } // Paper
@@ -2264,7 +2267,7 @@ public abstract class LivingEntity extends Entity {
 
     @Nullable
     public LivingEntity getKillCredit() {
-        return (LivingEntity) (this.combatTracker.getKiller() != null ? this.combatTracker.getKiller() : (this.lastHurtByPlayer != null ? this.lastHurtByPlayer : (this.lastHurtByMob != null ? this.lastHurtByMob : null)));
+        return (LivingEntity) (this.combatTracker.getKiller() != null ? this.combatTracker.getKiller() : (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() {
@@ -3432,7 +3435,7 @@ public abstract class LivingEntity extends Entity {
         this.pushEntities();
         this.level.getProfiler().pop();
         // Paper start
-        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)) {
             if (this.xo != 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());
@@ -4096,7 +4099,7 @@ public abstract class LivingEntity extends Entity {
         BlockPos blockposition = new BlockPos(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 49b983064ea810382b6112f5dc7f93ba4e5710bd..ee24904679e37007c38d3eb7095b406f345444f6 100644
--- a/src/main/java/net/minecraft/world/entity/Mob.java
+++ b/src/main/java/net/minecraft/world/entity/Mob.java
@@ -135,6 +135,14 @@ public abstract class Mob extends LivingEntity {
 
     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);
@@ -826,12 +834,7 @@ public abstract class Mob extends LivingEntity {
         if (this.level.getDifficulty() == Difficulty.PEACEFUL && this.shouldDespawnInPeaceful()) {
             this.discard();
         } else if (!this.isPersistenceRequired() && !this.requiresCustomPersistence()) {
-            // Paper start - optimise checkDespawn
-            Player entityhuman = this.level.findNearbyPlayer(this, level.paperConfig().entities.spawning.despawnRanges.get(this.getType().getCategory()).hard() + 1, EntitySelector.PLAYER_AFFECTS_SPAWNING); // Paper
-            if (entityhuman == null) {
-                entityhuman = ((ServerLevel)this.level).playersAffectingSpawning.isEmpty() ? null : ((ServerLevel)this.level).playersAffectingSpawning.get(0);
-            }
-            // Paper end - optimise checkDespawn
+            Player entityhuman = this.level.getNearestPlayer(this, -1.0D); // Folia - region threading
 
             if (entityhuman != null) {
                 double d0 = entityhuman.distanceToSqr((Entity) this);
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 11a101e8ff05fbda5e84018358be02014ca01854..8cfa70e9b07e0f993d172d3e4d3804490a4d9fd5 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.tamable.isOrderedToSit() ? false : this.tamable.distanceToSqr((Entity) this.owner) > (double) (this.stopDistance * this.stopDistance));
+        return this.navigation.isDone() ? false : (this.tamable.isOrderedToSit() ? false : (this.owner.level == this.level && this.tamable.distanceToSqr((Entity) this.owner) > (double) (this.stopDistance * this.stopDistance))); // Folia - region threading - check level
     }
 
     @Override
@@ -93,7 +93,7 @@ public class FollowOwnerGoal extends Goal {
         if (--this.timeToRecalcPath <= 0) {
             this.timeToRecalcPath = this.adjustedTickDelay(10);
             if (!this.tamable.isLeashed() && !this.tamable.isPassenger()) {
-                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);
@@ -105,6 +105,11 @@ 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);
@@ -135,7 +140,21 @@ public class FollowOwnerGoal extends Goal {
             }
             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/PathNavigation.java b/src/main/java/net/minecraft/world/entity/ai/navigation/PathNavigation.java
index 97257b450e848f53fdb9b5b7affa57b03ea5f459..5485eba13ae544a3e5b7ff5e416c369db8f9c7bc 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
@@ -79,11 +79,11 @@ 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 {
@@ -198,7 +198,7 @@ public abstract class PathNavigation {
 
     public boolean moveTo(Entity entity, double speed) {
         // Paper start - Pathfinding optimizations
-        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
@@ -210,7 +210,7 @@ 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
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 fed09b886f4fa0006d160e5f2abb00dfee45434d..394d73b10bc53310d936d1ad568a77bf852ef9d6 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.RegionisedWorldData 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.RegionisedWorldData.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.RegionisedWorldData 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;
                         }
                     }
@@ -108,7 +112,8 @@ 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.RegionisedWorldData 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;
@@ -143,7 +148,7 @@ 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 9be85eb0abec02bc0e0eded71c34ab1c565c63e7..9c56304476b4fc841b5d7694232617586ebd8e84 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/Cat.java b/src/main/java/net/minecraft/world/entity/animal/Cat.java
index 0114c1cf3b6b0500149a77ebc190cb7fa2832184..1189465e79005c99204f873ca7768171218d6399 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Cat.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Cat.java
@@ -366,7 +366,7 @@ 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 deadlock
+        if (world.structureManager().getStructureWithPieceAt(this.blockPosition(), StructureTags.CATS_SPAWN_AS_BLACK).isValid()) { // Paper - fix 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/animal/Turtle.java b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
index 25503678e7d049a8b3172cfad8a5606958c32302..13d60258c6c491a7d0ba5cc93934f0c9b2abd35b 100644
--- a/src/main/java/net/minecraft/world/entity/animal/Turtle.java
+++ b/src/main/java/net/minecraft/world/entity/animal/Turtle.java
@@ -336,9 +336,9 @@ public class Turtle extends Animal {
 
     @Override
     public void thunderHit(ServerLevel world, LightningBolt lightning) {
-        org.bukkit.craftbukkit.event.CraftEventFactory.entityDamage = lightning; // CraftBukkit
+        org.bukkit.craftbukkit.event.CraftEventFactory.entityDamageRT.set(lightning); // CraftBukkit // Folia - region threading
         this.hurt(DamageSource.LIGHTNING_BOLT, Float.MAX_VALUE);
-        org.bukkit.craftbukkit.event.CraftEventFactory.entityDamage = null; // CraftBukkit
+        org.bukkit.craftbukkit.event.CraftEventFactory.entityDamageRT.set(null); // CraftBukkit // Folia - region threading
     }
 
     private static class TurtleMoveControl extends MoveControl {
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 428523feaa4f30260e32ba03937e88200246c693..5722f1dd949c8ef59379bf4499ec2d77a40df847 100644
--- a/src/main/java/net/minecraft/world/entity/decoration/ItemFrame.java
+++ b/src/main/java/net/minecraft/world/entity/decoration/ItemFrame.java
@@ -290,8 +290,10 @@ 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/FallingBlockEntity.java b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
index eacb8a407fe99af2c13f23c12b5544696bda8890..723d5f44c59a8073040669549d9cab88b45e9a3e 100644
--- a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
@@ -292,9 +292,9 @@ public class FallingBlockEntity extends Entity {
                 float f2 = (float) Math.min(Mth.floor((float) i * this.fallDamagePerDistance), this.fallDamageMax);
 
                 this.level.getEntities((Entity) this, this.getBoundingBox(), predicate).forEach((entity) -> {
-                    CraftEventFactory.entityDamage = this; // CraftBukkit
+                    CraftEventFactory.entityDamageRT.set(this); // CraftBukkit // Folia - region threading
                     entity.hurt(damagesource1, f2);
-                    CraftEventFactory.entityDamage = null; // CraftBukkit
+                    CraftEventFactory.entityDamageRT.set(null); // CraftBukkit // Folia - region threading
                 });
                 boolean flag = this.blockState.is(BlockTags.ANVIL);
 
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 f0ccdfbd7d7be8c6e302609accf8fe9cac8885c4..d07060fb35df66e77ebdd404444c58564fdb9402 100644
--- a/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/ItemEntity.java
@@ -50,7 +50,7 @@ public class ItemEntity extends Entity {
     @Nullable
     private UUID owner;
     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
     private int despawnRate = -1; // Paper
     public net.kyori.adventure.util.TriState frictionState = net.kyori.adventure.util.TriState.NOT_SET; // Paper
@@ -116,13 +116,11 @@ public class ItemEntity extends Entity {
             this.discard();
         } 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();
@@ -176,11 +174,11 @@ public class ItemEntity extends Entity {
                 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) {
@@ -207,13 +205,14 @@ public class ItemEntity extends Entity {
     // 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
             // CraftBukkit start - fire ItemDespawnEvent
@@ -514,14 +513,20 @@ public class ItemEntity extends Entity {
         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 bedee2c93bd0aff148f93dcf111e0fc3d9bce4a0..718701a39d0c5369600119330cec7f8015fd95b0 100644
--- a/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
+++ b/src/main/java/net/minecraft/world/entity/item/PrimedTnt.java
@@ -59,7 +59,7 @@ public class PrimedTnt extends Entity {
 
     @Override
     public void tick() {
-        if (level.spigotConfig.maxTntTicksPerTick > 0 && ++level.spigotConfig.currentPrimedTnt > level.spigotConfig.maxTntTicksPerTick) { return; } // Spigot
+        if (level.spigotConfig.maxTntTicksPerTick > 0 && ++level.getCurrentWorldData().currentPrimedTnt > level.spigotConfig.maxTntTicksPerTick) { return; } // Spigot // Folia - region threading
         if (!this.isNoGravity()) {
             this.setDeltaMovement(this.getDeltaMovement().add(0.0D, -0.04D, 0.0D));
         }
@@ -101,7 +101,7 @@ public class PrimedTnt extends Entity {
              */
             // 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/Zombie.java b/src/main/java/net/minecraft/world/entity/monster/Zombie.java
index 9976205537cfe228735687f1e9c52c74ac025690..f286abfff186b657db99f28d3592465ccee4498a 100644
--- a/src/main/java/net/minecraft/world/entity/monster/Zombie.java
+++ b/src/main/java/net/minecraft/world/entity/monster/Zombie.java
@@ -94,7 +94,7 @@ 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
 
     public Zombie(EntityType<? extends Zombie> type, Level world) {
@@ -217,10 +217,7 @@ 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();
                 }
@@ -237,7 +234,7 @@ public class Zombie extends Monster {
         }
 
         super.tick();
-        this.lastTick = MinecraftServer.currentTick; // CraftBukkit
+        //this.lastTick = MinecraftServer.currentTick; // CraftBukkit // Folia - region threading - restore original timers
     }
 
     @Override
@@ -276,7 +273,7 @@ public class Zombie extends Monster {
     }
     // Paper end
     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 71a36cf9b976443cca9ab63cd0eb23253f638562..c7a03304d8fb33e2e5c90547cba46665b51eec79 100644
--- a/src/main/java/net/minecraft/world/entity/monster/ZombieVillager.java
+++ b/src/main/java/net/minecraft/world/entity/monster/ZombieVillager.java
@@ -70,7 +70,7 @@ 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);
@@ -145,10 +145,7 @@ 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) {
@@ -157,7 +154,7 @@ 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 ca96b893e22de3ae7c11d5cded51edf70bdcb6f2..6000e891620850aac303630bf6676085d41f65b5 100644
--- a/src/main/java/net/minecraft/world/entity/npc/AbstractVillager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/AbstractVillager.java
@@ -213,10 +213,18 @@ 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 5f407535298a31a34cfe114dd863fd6a9b977707..1f1e3d6e5e94b985a5c929ab266a996471432923 100644
--- a/src/main/java/net/minecraft/world/entity/npc/CatSpawner.java
+++ b/src/main/java/net/minecraft/world/entity/npc/CatSpawner.java
@@ -21,17 +21,18 @@ 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.RegionisedWorldData 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 18eac340386a396c9850f53f30d20a41c1437788..81efaadf67f7bcc6097c19c05ba2fdb6b34d8218 100644
--- a/src/main/java/net/minecraft/world/entity/npc/Villager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/Villager.java
@@ -710,6 +710,8 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
                 ServerLevel worldserver = minecraftserver.getLevel(globalpos.dimension());
 
                 if (worldserver != null) {
+                    io.papermc.paper.threadedregions.RegionisedServer.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);
@@ -718,6 +720,7 @@ 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 0ae8e9134a3671cdf2a480cd4dd6598653e261ab..d9d832b7978d03417912408564f6e21bb5e52dc3 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
-        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.RegionisedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
         // Paper start
-        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.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
                     //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
                     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
                         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/projectile/EvokerFangs.java b/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java
index c7265a650a5d6bdc42d41c5c90cad401d7f1c99d..c95d80ee142dc056874af6baf2d058cc932985e9 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/EvokerFangs.java
@@ -128,9 +128,9 @@ public class EvokerFangs extends Entity {
 
         if (target.isAlive() && !target.isInvulnerable() && target != entityliving1) {
             if (entityliving1 == null) {
-                org.bukkit.craftbukkit.event.CraftEventFactory.entityDamage = this; // CraftBukkit
+                org.bukkit.craftbukkit.event.CraftEventFactory.entityDamageRT.set(this); // CraftBukkit // Folia - region threading
                 target.hurt(DamageSource.MAGIC, 6.0F);
-                org.bukkit.craftbukkit.event.CraftEventFactory.entityDamage = null; // CraftBukkit
+                org.bukkit.craftbukkit.event.CraftEventFactory.entityDamageRT.set(null); // CraftBukkit // Folia - region threading
             } else {
                 if (entityliving1.isAlliedTo((Entity) target)) {
                     return;
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 5406925cd66f46ab8744123c670d72cea7bfc3a1..d0fa197283a3bf14ead356e832500430ecae3f86 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/FireworkRocketEntity.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/FireworkRocketEntity.java
@@ -130,6 +130,10 @@ public class FireworkRocketEntity extends Projectile implements ItemSupplier {
 
                 });
             }
+            if (this.attachedToEntity != null && !io.papermc.paper.util.TickThread.isTickThreadFor(this.attachedToEntity)) { // Folia start - region threading
+                this.attachedToEntity = null;
+            }
+            // Folia end - region threading
 
             if (this.attachedToEntity != null) {
                 if (this.attachedToEntity.isFallFlying()) {
@@ -241,9 +245,9 @@ public class FireworkRocketEntity extends Projectile implements ItemSupplier {
 
         if (f > 0.0F) {
             if (this.attachedToEntity != null) {
-                CraftEventFactory.entityDamage = this; // CraftBukkit
+                CraftEventFactory.entityDamageRT.set(this); // CraftBukkit // Folia - region threading
                 this.attachedToEntity.hurt(DamageSource.fireworks(this, this.getOwner()), 5.0F + (float) (nbttaglist.size() * 2));
-                CraftEventFactory.entityDamage = null; // CraftBukkit
+                CraftEventFactory.entityDamageRT.set(null); // CraftBukkit // Folia - region threading
             }
 
             double d0 = 5.0D;
@@ -270,9 +274,9 @@ public class FireworkRocketEntity extends Projectile implements ItemSupplier {
                     if (flag) {
                         float f1 = f * (float) Math.sqrt((5.0D - (double) this.distanceTo(entityliving)) / 5.0D);
 
-                        CraftEventFactory.entityDamage = this; // CraftBukkit
+                        CraftEventFactory.entityDamageRT.set(this); // CraftBukkit // Folia - region threading
                         entityliving.hurt(DamageSource.fireworks(this, this.getOwner()), f1);
-                        CraftEventFactory.entityDamage = null; // CraftBukkit
+                        CraftEventFactory.entityDamageRT.set(null); // CraftBukkit // Folia - region threading
                     }
                 }
             }
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 66476b33cede1e44db5ec166a0cea81f82ffe47a..26a17e3098317f6f623cdcab59dceb9d213c7f63 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
@@ -52,8 +52,19 @@ public abstract class Projectile extends Entity {
 
     }
 
+    // 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
     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()) {
             return this.cachedOwner;
         } else if (this.ownerUUID != null && this.level instanceof ServerLevel) {
@@ -273,6 +284,6 @@ public abstract class Projectile extends Entity {
     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
     }
 }
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 00ac1cdc4734cc57f15433c5c6e7a3a545739d33..39b0034b7c612759fed87b6a5fff1819583f3f85 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/SmallFireball.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/SmallFireball.java
@@ -23,7 +23,7 @@ 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
             isIncendiary = this.level.getGameRules().getBoolean(GameRules.RULE_MOBGRIEFING);
         }
         // CraftBukkit end
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 f224ebbc0efefddede43d87f0300c014077b9931..2627610b77e779722bb33eeb1096d862aa9639d2 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
@@ -44,6 +44,62 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
         entityHitResult.getEntity().hurt(DamageSource.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
+
+                if (entity.getLevel() != 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.getLevel();
+
+                            // endermite spawn chance
+                            if (world.random.nextFloat() < 0.05F && world.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING)) {
+                                Endermite entityendermite = EntityType.ENDERMITE.create(world);
+
+                                if (entityendermite != null) {
+                                    entityendermite.moveTo(player.getX(), player.getY(), player.getZ(), player.getYRot(), player.getXRot());
+                                    world.addFreshEntity(entityendermite, CreatureSpawnEvent.SpawnReason.ENDER_PEARL);
+                                }
+                            }
+
+                            // damage player
+                            player.hurt(DamageSource.FALL, 5.0F);
+                        }
+                    }
+                );
+            },
+            null,
+            1L
+        );
+    }
+    // Folia end - region threading
+
     @Override
     protected void onHit(HitResult hitResult) {
         super.onHit(hitResult);
@@ -53,6 +109,20 @@ 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.getLevel(), this.position());
+                }
+                this.discard();
+                return;
+            }
+            // Folia end - region threading
             Entity entity = this.getOwner();
 
             if (entity instanceof ServerPlayer) {
@@ -84,9 +154,9 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
 
                         entityplayer.connection.teleport(teleEvent.getTo());
                         entity.resetFallDistance();
-                        CraftEventFactory.entityDamage = this;
+                        CraftEventFactory.entityDamageRT.set(this); // Folia - region threading
                         entity.hurt(DamageSource.FALL, 5.0F);
-                        CraftEventFactory.entityDamage = null;
+                        CraftEventFactory.entityDamageRT.set(null); // Folia - region threading
                     }
                     // CraftBukkit end
                 }
@@ -112,6 +182,14 @@ 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 08b18428e867baf14f551beb72e3875b0c420639..941e74fe6f66a1e7d1a909e2dcf494eba0704058 100644
--- a/src/main/java/net/minecraft/world/entity/raid/Raid.java
+++ b/src/main/java/net/minecraft/world/entity/raid/Raid.java
@@ -108,6 +108,13 @@ public class Raid {
     private int celebrationTicks;
     private Optional<BlockPos> waveSpawnPos;
 
+    // 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();
@@ -213,7 +220,7 @@ 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
         };
     }
 
@@ -527,7 +534,7 @@ 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 e5ccbaf72f29731f1d1aa939b9297b644a408cd4..1792655d2f0357b388b3c83886cac4bc109e1aa9 100644
--- a/src/main/java/net/minecraft/world/entity/raid/Raider.java
+++ b/src/main/java/net/minecraft/world/entity/raid/Raider.java
@@ -91,7 +91,7 @@ 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 feb89eb69994bdd1d2f95d2b9992e69251b2bee7..39cdb5c0080613662eaefc4f94d17fa1bd25ed30 100644
--- a/src/main/java/net/minecraft/world/entity/raid/Raids.java
+++ b/src/main/java/net/minecraft/world/entity/raid/Raids.java
@@ -28,14 +28,14 @@ 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 Raids(ServerLevel world) {
         this.level = world;
-        this.nextAvailableID = 1;
+        this.nextAvailableID.set(1); // Folia - make raids thread-safe
         this.setDirty();
     }
 
@@ -43,12 +43,26 @@ 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();
@@ -62,14 +76,17 @@ 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;
     }
 
@@ -82,7 +99,7 @@ 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();
@@ -162,7 +179,7 @@ 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);
 
@@ -178,7 +195,7 @@ 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();
@@ -200,7 +217,7 @@ public class Raids extends SavedData {
     }
 
     private int getUniqueId() {
-        return ++this.nextAvailableID;
+        return this.nextAvailableID.incrementAndGet(); // Folia - make raids thread-safe
     }
 
     @Nullable
@@ -211,6 +228,11 @@ 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/MinecartHopper.java b/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java
index 70f1916185b79bbb9f033f4ef8119d7b17a13ef8..54d55e8827f4ab286fca722f199aac42cddab8d2 100644
--- a/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java
+++ b/src/main/java/net/minecraft/world/entity/vehicle/MinecartHopper.java
@@ -155,7 +155,7 @@ 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.RegionisedServer.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 9c8604376228c02f8bbd9a15673fbdf5097e7cb2..40410ce889ef18344291f04d29938b4d1d3c9766 100644
--- a/src/main/java/net/minecraft/world/item/ArmorItem.java
+++ b/src/main/java/net/minecraft/world/item/ArmorItem.java
@@ -63,7 +63,7 @@ public class ArmorItem extends Item implements Wearable {
             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 6860096cb8c0deecc9c1d87543d1128fb95fd2d4..00cc67322d7de29c30b54aa7da62cc44d6469a1d 100644
--- a/src/main/java/net/minecraft/world/item/ItemStack.java
+++ b/src/main/java/net/minecraft/world/item/ItemStack.java
@@ -333,6 +333,7 @@ public final class ItemStack {
     }
 
     public InteractionResult useOn(UseOnContext itemactioncontext, InteractionHand enumhand) { // CraftBukkit - add hand
+
         net.minecraft.world.entity.player.Player entityhuman = itemactioncontext.getPlayer();
         BlockPos blockposition = itemactioncontext.getClickedPos();
         BlockInWorld shapedetectorblock = new BlockInWorld(itemactioncontext.getLevel(), blockposition, false);
@@ -344,12 +345,13 @@ public final class ItemStack {
             CompoundTag oldData = this.getTagClone();
             int oldCount = this.getCount();
             ServerLevel world = (ServerLevel) itemactioncontext.getLevel();
+            io.papermc.paper.threadedregions.RegionisedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
 
             if (!(this.getItem() instanceof BucketItem/* || this.getItem() instanceof SolidBucketItem*/)) { // if not bucket // Paper - capture block states for snow buckets
-                world.captureBlockStates = true;
+                worldData.captureBlockStates = true; // Folia - region threading
                 // special case bonemeal
                 if (this.getItem() == Items.BONE_MEAL) {
-                    world.captureTreeGeneration = true;
+                    worldData.captureTreeGeneration = true; // Folia - region threading
                 }
             }
             Item item = this.getItem();
@@ -358,14 +360,14 @@ public final class ItemStack {
             int newCount = this.getCount();
             this.setCount(oldCount);
             this.setTagClone(oldData);
-            world.captureBlockStates = false;
-            if (enuminteractionresult.consumesAction() && world.captureTreeGeneration && world.capturedBlockStates.size() > 0) {
-                world.captureTreeGeneration = false;
+            worldData.captureBlockStates = false; // Folia - region threading
+            if (enuminteractionresult.consumesAction() && worldData.captureTreeGeneration && worldData.capturedBlockStates.size() > 0) { // Folia - region threading
+                world.getCurrentWorldData().captureTreeGeneration = false; // Folia - region threading
                 Location location = new Location(world.getWorld(), blockposition.getX(), blockposition.getY(), blockposition.getZ());
                 TreeType treeType = SaplingBlock.treeType;
                 SaplingBlock.treeType = 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
                 StructureGrowEvent structureEvent = null;
                 if (treeType != null) {
                     boolean isBonemeal = this.getItem() == Items.BONE_MEAL;
@@ -392,12 +394,12 @@ public final class ItemStack {
                 SignItem.openSign = null; // SPIGOT-6758 - Reset on early return
                 return enuminteractionresult;
             }
-            world.captureTreeGeneration = false;
+            worldData.captureTreeGeneration = false; // Folia - region threading
 
             if (entityhuman != null && enuminteractionresult.shouldAwardStats()) {
                 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 - don't call event twice for snow buckets
@@ -408,13 +410,13 @@ public final class ItemStack {
                     enuminteractionresult = InteractionResult.FAIL; // cancel placement
                     // PAIL: Remove this when MC-99075 fixed
                     placeEvent.getPlayer().updateInventory();
-                    world.capturedTileEntities.clear(); // Paper - clear out tile entities as chests and such will pop loot
+                    worldData.capturedTileEntities.clear(); // Paper - clear out tile 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
                     BlockPos placedPos = ((CraftBlock) placeEvent.getBlock()).getPosition();
@@ -429,7 +431,7 @@ 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());
                     }
 
@@ -490,8 +492,8 @@ 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 586852e347cfeb6e52d16e51b3f193e814036e81..eacd5b6f649a59f845cc8d9d9373d41ed3757c97 100644
--- a/src/main/java/net/minecraft/world/item/MapItem.java
+++ b/src/main/java/net/minecraft/world/item/MapItem.java
@@ -103,6 +103,7 @@ 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;
@@ -134,9 +135,9 @@ public class MapItem extends ComplexItem {
                             int j2 = (j / i + k1 - 64) * i;
                             int k2 = (k / i + l1 - 64) * i;
                             Multiset<MaterialColor> 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 this remains true
 
-                            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;
@@ -227,6 +228,7 @@ public class MapItem extends ComplexItem {
             }
 
         }
+        } // Folia - make map data thread-safe
     }
 
     private BlockState getCorrectStateForFluidBlock(Level world, BlockState state, BlockPos pos) {
@@ -243,6 +245,7 @@ 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;
@@ -317,6 +320,7 @@ public class MapItem extends ComplexItem {
                 }
 
             }
+            } // Folia - make map data thread-safe
         }
     }
 
@@ -326,6 +330,7 @@ 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;
 
@@ -335,6 +340,7 @@ 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 c6d2f764efa9b8bec730bbe757d480e365b25ccc..af9313a3b3aaa0af4f2a2f4fb2424dc3e9140d9c 100644
--- a/src/main/java/net/minecraft/world/item/MinecartItem.java
+++ b/src/main/java/net/minecraft/world/item/MinecartItem.java
@@ -67,7 +67,7 @@ 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/level/BaseCommandBlock.java b/src/main/java/net/minecraft/world/level/BaseCommandBlock.java
index 888936385196a178ab8b730fd5e4fff4a5466428..df4632a6ddef8744df160163c99bdcdd6225dd97 100644
--- a/src/main/java/net/minecraft/world/level/BaseCommandBlock.java
+++ b/src/main/java/net/minecraft/world/level/BaseCommandBlock.java
@@ -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");
diff --git a/src/main/java/net/minecraft/world/level/EntityGetter.java b/src/main/java/net/minecraft/world/level/EntityGetter.java
index 3b959f42d958bf0f426853aee56753d6c455fcdb..b1a6a66ed02706c1adc36dcedfa415f5a24a25a0 100644
--- a/src/main/java/net/minecraft/world/level/EntityGetter.java
+++ b/src/main/java/net/minecraft/world/level/EntityGetter.java
@@ -38,6 +38,12 @@ 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) {
@@ -92,7 +98,7 @@ public interface EntityGetter {
         double d = -1.0D;
         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 < 0.0D || e < maxDistance * maxDistance) && (d == -1.0D || e < d)) {
@@ -113,7 +119,7 @@ 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);
 
@@ -140,7 +146,7 @@ public interface EntityGetter {
 
     // Paper start
     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) {
@@ -153,7 +159,7 @@ public interface EntityGetter {
     // Paper end
 
     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 < 0.0D || d < range * range) {
@@ -167,17 +173,17 @@ 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, (LivingEntity)null, x, y, z);
+        return this.getNearestEntity(this.getLocalPlayers(), targetPredicate, (LivingEntity)null, x, y, z); // Folia - region threading
     }
 
     @Nullable
@@ -208,7 +214,7 @@ 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);
             }
@@ -234,8 +240,7 @@ 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 a213f4098859858a73ddd601bbe8c7511972e0d5..07aa859ccfd3283097c172672c5d80130187cd4c 100644
--- a/src/main/java/net/minecraft/world/level/Explosion.java
+++ b/src/main/java/net/minecraft/world/level/Explosion.java
@@ -246,7 +246,7 @@ public class Explosion {
                             continue;
                         }
 
-                        CraftEventFactory.entityDamage = this.source;
+                        CraftEventFactory.entityDamageRT.set(this.source); // Folia - region threading
                         entity.lastDamageCancelled = false;
 
                         if (entity instanceof EnderDragon) {
@@ -259,7 +259,7 @@ public class Explosion {
                             entity.hurt(this.getDamageSource(), (float) ((int) ((d13 * d13 + d13) / 2.0D * 7.0D * (double) f2 + 1.0D)));
                         }
 
-                        CraftEventFactory.entityDamage = null;
+                        CraftEventFactory.entityDamageRT.set(null); // Folia - region threading
                         if (entity.lastDamageCancelled) { // SPIGOT-5339, SPIGOT-6252, SPIGOT-6777: Skip entity if damage event was cancelled
                             continue;
                         }
@@ -503,17 +503,10 @@ public class Explosion {
     }
     // Paper start - Optimize explosions
     private float getBlockDensity(Vec3 vec3d, Entity entity) {
-        if (!this.level.paperConfig().environment.optimizeExplosions) {
+        if (true || !this.level.paperConfig().environment.optimizeExplosions) { // Folia - region threading
             return getSeenPercent(vec3d, entity);
         }
-        CacheKey key = new CacheKey(this, entity.getBoundingBox());
-        Float blockDensity = this.level.explosionDensityCache.get(key);
-        if (blockDensity == null) {
-            blockDensity = getSeenPercent(vec3d, entity);
-            this.level.explosionDensityCache.put(key, blockDensity);
-        }
-
-        return blockDensity;
+        return 0.0f; // Folia - region threading
     }
 
     static class CacheKey {
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 60003ff929f7ac6b34f9230c53ccbd54dc9e176b..54f50326beaef3985277ff941e40415a671f31fb 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -116,10 +116,10 @@ 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;
-    protected final List<TickingBlockEntity> blockEntityTickers = Lists.newArrayList(); public final int getTotalTileEntityTickers() { return this.blockEntityTickers.size(); } // Paper
-    protected final NeighborUpdater neighborUpdater;
-    private final List<TickingBlockEntity> pendingBlockEntityTickers = Lists.newArrayList();
-    private boolean tickingBlockEntities;
+    //protected final List<TickingBlockEntity> blockEntityTickers = Lists.newArrayList(); public final int getTotalTileEntityTickers() { return this.blockEntityTickers.size(); } // Paper // Folia - region threading
+    public final int neighbourUpdateMax; //protected final NeighborUpdater neighborUpdater;
+    //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;
@@ -129,7 +129,7 @@ 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();
@@ -141,7 +141,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     private final WorldBorder worldBorder;
     private final BiomeManager biomeManager;
     private final ResourceKey<Level> dimension;
-    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 org.bukkit.generator.ChunkGenerator generator;
     public static final boolean DEBUG_ENTITIES = Boolean.getBoolean("debug.entities"); // Paper
 
-    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
-    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
     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 - 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 - Move from Map in BlockRedstoneTorch to here // Folia - region threading
 
     // Paper start - fix and optimise world upgrading
     // copied from below
@@ -223,7 +213,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         List<net.minecraft.server.level.ServerPlayer> ret = new java.util.ArrayList<>();
         double maxRangeSquared = maxRange * maxRange;
 
-        for (net.minecraft.server.level.ServerPlayer player : (List<net.minecraft.server.level.ServerPlayer>)this.players()) {
+        for (net.minecraft.server.level.ServerPlayer player : (List<net.minecraft.server.level.ServerPlayer>)this.getLocalPlayers()) { // Folia - region threading
             if ((maxRange < 0.0 || player.distanceToSqr(sourceX, sourceY, sourceZ) < maxRangeSquared)) {
                 if (predicate == null || predicate.test(player)) {
                     ret.add(player);
@@ -239,7 +229,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         net.minecraft.server.level.ServerPlayer closest = null;
         double closestRangeSquared = maxRange < 0.0 ? Double.MAX_VALUE : maxRange * maxRange;
 
-        for (net.minecraft.server.level.ServerPlayer player : (List<net.minecraft.server.level.ServerPlayer>)this.players()) {
+        for (net.minecraft.server.level.ServerPlayer player : (List<net.minecraft.server.level.ServerPlayer>)this.getLocalPlayers()) { // Folia - region threading
             double distanceSquared = player.distanceToSqr(sourceX, sourceY, sourceZ);
             if (distanceSquared < closestRangeSquared && (predicate == null || predicate.test(player))) {
                 closest = player;
@@ -270,6 +260,24 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     public abstract ResourceKey<LevelStem> getTypeKey();
 
+    // Folia start - region ticking
+    public final io.papermc.paper.threadedregions.RegionisedData<io.papermc.paper.threadedregions.RegionisedWorldData> worldRegionData
+        = new io.papermc.paper.threadedregions.RegionisedData<>(
+            (ServerLevel)this, () -> new io.papermc.paper.threadedregions.RegionisedWorldData((ServerLevel)Level.this),
+            io.papermc.paper.threadedregions.RegionisedWorldData.REGION_CALLBACK
+    );
+    public volatile io.papermc.paper.threadedregions.RegionisedServer.WorldLevelData tickData;
+
+    public io.papermc.paper.threadedregions.RegionisedWorldData getCurrentWorldData() {
+        return io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData();
+    }
+
+    @Override
+    public List<net.minecraft.server.level.ServerPlayer> getLocalPlayers() {
+        return this.getCurrentWorldData().getLocalPlayers();
+    }
+    // Folia end - region ticking
+
     protected Level(WritableLevelData worlddatamutable, ResourceKey<Level> resourcekey, 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 - 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
@@ -313,7 +321,7 @@ 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
         // CraftBukkit start
         this.getWorldBorder().world = (ServerLevel) this;
         // From PlayerList.setPlayerFileData
@@ -452,8 +460,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     @Nullable
     public final BlockState getBlockStateIfLoaded(BlockPos blockposition) {
         // CraftBukkit start - tree generation
-        if (captureTreeGeneration) {
-            CraftBlockState previous = capturedBlockStates.get(blockposition);
+        if (this.getCurrentWorldData().captureTreeGeneration) { // Folia - region threading
+            CraftBlockState previous = this.getCurrentWorldData().capturedBlockStates.get(blockposition); // Folia - region threading
             if (previous != null) {
                 return previous.getHandle();
             }
@@ -514,16 +522,17 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Override
     public boolean setBlock(BlockPos pos, BlockState state, int flags, int maxUpdateDepth) {
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = this.getCurrentWorldData(); // Folia - region threading
         // CraftBukkit start - tree generation
-        if (this.captureTreeGeneration) {
+        if (worldData.captureTreeGeneration) { // Folia - region threading
             // Paper start
             BlockState type = getBlockState(pos);
             if (!type.isDestroyable()) return false;
             // Paper end
-            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);
             return true;
@@ -539,10 +548,10 @@ 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
@@ -552,8 +561,8 @@ 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;
@@ -596,7 +605,7 @@ 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 {
@@ -645,7 +654,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
                 // CraftBukkit start
                 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();
-                if (world != null && ((ServerLevel)this).hasPhysicsEvent) { // Paper
+                if (world != null && ((ServerLevel)this).getCurrentWorldData().hasPhysicsEvent) { // Paper // Folia - region threading
                     BlockPhysicsEvent event = new BlockPhysicsEvent(world.getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ()), CraftBlockData.fromData(iblockdata));
                     this.getCraftServer().getPluginManager().callEvent(event);
 
@@ -659,7 +668,7 @@ 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
@@ -738,7 +747,7 @@ 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
@@ -763,11 +772,24 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         return this.getChunkSource().getLightEngine();
     }
 
+    // Folia start - region threading
+    @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();
             }
@@ -858,7 +880,7 @@ 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() {
@@ -866,11 +888,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
         gameprofilerfiller.push("blockEntities");
         timings.tileEntityPending.startTiming(); // Spigot
-        this.tickingBlockEntities = true;
-        if (!this.pendingBlockEntityTickers.isEmpty()) {
-            this.blockEntityTickers.addAll(this.pendingBlockEntityTickers);
-            this.pendingBlockEntityTickers.clear();
-        }
+        final io.papermc.paper.threadedregions.RegionisedWorldData regionisedWorldData = ((ServerLevel)this).getCurrentWorldData(); // Folia - regionised ticking
+        regionisedWorldData.seTtickingBlockEntities(true); // Folia - regionised ticking
+        regionisedWorldData.pushPendingTickingBlockEntities(); // Folia - regionised ticking
+        List<TickingBlockEntity> blockEntityTickers = regionisedWorldData.getBlockEntityTickers(); // Folia - regionised ticking
         timings.tileEntityPending.stopTiming(); // Spigot
 
         timings.tileEntityTick.startTiming(); // Spigot
@@ -879,9 +900,8 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         int tilesThisCycle = 0;
         var toRemove = new it.unimi.dsi.fastutil.objects.ObjectOpenCustomHashSet<TickingBlockEntity>(net.minecraft.Util.identityStrategy()); // Paper - use removeAll
         toRemove.add(null);
-        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(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 start
             if (tickingblockentity == null) {
                 this.getCraftServer().getLogger().severe("Spigot has detected a null entity and has removed it, preventing a crash");
@@ -898,19 +918,19 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
             } else if (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);
+        blockEntityTickers.removeAll(toRemove); // Folia - regionised ticking
 
         timings.tileEntityTick.stopTiming(); // Spigot
-        this.tickingBlockEntities = false;
-        co.aikar.timings.TimingHistory.tileEntityTicks += this.blockEntityTickers.size(); // Paper
+        regionisedWorldData.seTtickingBlockEntities(false); // Folia - regionised ticking
+        //co.aikar.timings.TimingHistory.tileEntityTicks += this.blockEntityTickers.size(); // Paper // Folia - region threading
         gameprofilerfiller.pop();
-        spigotConfig.currentPrimedTnt = 0; // Spigot
+        regionisedWorldData.currentPrimedTnt = 0; // Spigot // Folia - region threading
     }
 
     public <T extends Entity> void guardEntityTick(Consumer<T> tickConsumer, T entity) {
@@ -1008,7 +1028,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public BlockEntity getBlockEntity(BlockPos blockposition, boolean validate) {
         // Paper start - 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
@@ -1021,8 +1041,8 @@ 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
@@ -1226,13 +1246,30 @@ 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.RegionisedWorldData 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.RegionisedWorldData 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;
@@ -1438,8 +1475,7 @@ 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
@@ -1470,7 +1506,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
 
     @Override
     public long nextSubTickCount() {
-        return (long) (this.subTickCount++);
+        return this.subTickCount.getAndIncrement(); // Folia - region threading
     }
 
     public static enum ExplosionInteraction {
diff --git a/src/main/java/net/minecraft/world/level/LevelAccessor.java b/src/main/java/net/minecraft/world/level/LevelAccessor.java
index 73d1adc5ddf0363966eac0c77c8dfbbb20a2b6a3..375a2b57bcb29458443c1a4e2be3c0e5f4e6019c 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 7fe1b8856bf916796fa6d2a984f0a07a2331e23b..07802d0a25e49519c3c9b33c217e05002cf05e31 100644
--- a/src/main/java/net/minecraft/world/level/LevelReader.java
+++ b/src/main/java/net/minecraft/world/level/LevelReader.java
@@ -135,6 +135,15 @@ public interface LevelReader extends BlockAndTintGetter, CollisionGetter, BiomeM
         return this.getChunk(chunkX, chunkZ, ChunkStatus.FULL, true);
     }
 
+    // Folia start - region threaeding
+    default ChunkAccess syncLoadNonFull(int chunkX, int chunkZ, ChunkStatus status) {
+        if (status == null || status.isOrAfter(ChunkStatus.FULL)) {
+            throw new IllegalArgumentException("Status: " + status.getName());
+        }
+        return this.getChunk(chunkX, chunkZ, status, true);
+    }
+    // Folia end - region threaeding
+
     default ChunkAccess getChunk(int chunkX, int chunkZ, ChunkStatus status) {
         return this.getChunk(chunkX, chunkZ, status, true);
     }
@@ -204,6 +213,25 @@ public interface LevelReader extends BlockAndTintGetter, CollisionGetter, BiomeM
         return maxY >= this.getMinBuildHeight() && minY < this.getMaxBuildHeight() ? this.hasChunksAt(minX, minZ, maxX, maxZ) : false;
     }
 
+    // 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 */
     @Deprecated
     default boolean hasChunksAt(int minX, int minZ, int maxX, int maxZ) {
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 01b21f520ef1c834b9bafc3de85c1fa4fcf539d6..99bc2e30e3a35929de7cff65bf0a69f25d93d5c2 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -115,11 +115,7 @@ public final class NaturalSpawner {
                     }
 
                     object2intopenhashmap.addTo(enumcreaturetype, 1);
-                    // Paper start
-                    if (countMobs) {
-                        chunk.level.getChunkSource().chunkMap.updatePlayerMobTypeMap(entity);
-                    }
-                    // Paper end
+                    // Folia - rewrite chunk system - revert per player mob caps
                 });
             }
         }
@@ -146,7 +142,7 @@ 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);
             }
 
@@ -154,37 +150,13 @@ public final class NaturalSpawner {
                 continue;
             }
 
-            // Paper start - only allow spawns upto the limit per chunk and update count afterwards
-            int currEntityCount = info.mobCategoryCounts.getInt(enumcreaturetype);
-            int k1 = limit * info.getSpawnableChunkCount() / NaturalSpawner.MAGIC_NUMBER;
-            int difference = k1 - currEntityCount;
-
-            if (world.paperConfig().entities.spawning.perPlayerMobSpawns) {
-                int minDiff = Integer.MAX_VALUE;
-                final com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> inRange = world.getChunkSource().chunkMap.playerMobDistanceMap.getObjectsInRange(chunk.getPos());
-                if (inRange != null) {
-                    final Object[] backingSet = inRange.getBackingSet();
-                    for (int k = 0; k < backingSet.length; k++) {
-                        if (!(backingSet[k] instanceof final net.minecraft.server.level.ServerPlayer player)) {
-                            continue;
-                        }
-                        minDiff = Math.min(limit - world.getChunkSource().chunkMap.getMobCountNear(player, enumcreaturetype), minDiff);
-                    }
-                }
-                difference = (minDiff == Integer.MAX_VALUE) ? 0 : minDiff;
-            }
-            if ((spawnAnimals || !enumcreaturetype.isFriendly()) && (spawnMonsters || enumcreaturetype.isFriendly()) && (rareSpawn || !enumcreaturetype.isPersistent()) && difference > 0) {
-                // Paper end
+            if ((spawnAnimals || !enumcreaturetype.isFriendly()) && (spawnMonsters || enumcreaturetype.isFriendly()) && (rareSpawn || !enumcreaturetype.isPersistent()) && info.canSpawnForCategory(enumcreaturetype, chunk.getPos(), limit)) { // Folia - region threading - revert per player mob caps
                 // CraftBukkit end
                 Objects.requireNonNull(info);
                 NaturalSpawner.SpawnPredicate spawnercreature_c = info::canSpawn;
 
                 Objects.requireNonNull(info);
-                // Paper start
-                int spawnCount = NaturalSpawner.spawnCategoryForChunk(enumcreaturetype, world, chunk, spawnercreature_c, info::afterSpawn,
-                    difference, world.paperConfig().entities.spawning.perPlayerMobSpawns ? world.getChunkSource().chunkMap::updatePlayerMobTypeMap : null);
-                info.mobCategoryCounts.mergeInt(enumcreaturetype, spawnCount, Integer::sum);
-                // Paper end
+                NaturalSpawner.spawnCategoryForChunk(enumcreaturetype, world, chunk, spawnercreature_c, info::afterSpawn); // Folia - region threading - revert per player mob caps
             }
         }
 
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 bad7031426ae6c750ae4376beb238186e7d65270..070d8fe9e016ad03be2c1fb5f22379f80ad3f155 100644
--- a/src/main/java/net/minecraft/world/level/StructureManager.java
+++ b/src/main/java/net/minecraft/world/level/StructureManager.java
@@ -44,11 +44,8 @@ public class StructureManager {
     }
 
     public List<StructureStart> startsForStructure(ChunkPos pos, Predicate<Structure> predicate) {
-        // Paper start
-        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();
+        // Folia - region threading
+        Map<Structure, LongSet> map = this.level.getChunk(pos.x, pos.z, ChunkStatus.STRUCTURE_REFERENCES).getAllReferences();
         // Paper end
         ImmutableList.Builder<StructureStart> builder = ImmutableList.builder();
 
@@ -113,18 +110,14 @@ public class StructureManager {
     }
 
     public StructureStart getStructureWithPieceAt(BlockPos pos, TagKey<Structure> structureTag) {
-        // Paper start
-        return this.getStructureWithPieceAt(pos, structureTag, null);
-    }
-    public StructureStart getStructureWithPieceAt(BlockPos pos, TagKey<Structure> structureTag, @Nullable ServerLevelAccessor levelAccessor) {
-        // Paper end
+        // Folia - region threading
         Registry<Structure> registry = this.registryAccess().registryOrThrow(Registries.STRUCTURE);
 
         for(StructureStart structureStart : this.startsForStructure(new ChunkPos(pos), (structure) -> {
             return registry.getHolder(registry.getId(structure)).map((reference) -> {
                 return reference.is(structureTag);
             }).orElse(false);
-        }, levelAccessor)) { // Paper
+        })) { // Paper // Folia - region threading
             if (this.structureHasPieceAt(pos, structureStart)) {
                 return structureStart;
             }
@@ -168,7 +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/Block.java b/src/main/java/net/minecraft/world/level/block/Block.java
index 7b71073027f4cf79736546500ededdfbb83d968e..6c6b7b94e875dce36619461e3994b148148e7f8a 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 03fde6e47c4a347c62fe9b4a3351769aedf874f6..d2e3e1d20d60f5edd0d93709b808f812c31e7491 100644
--- a/src/main/java/net/minecraft/world/level/block/BushBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/BushBlock.java
@@ -24,7 +24,7 @@ public 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/CactusBlock.java b/src/main/java/net/minecraft/world/level/block/CactusBlock.java
index 1ec242205b82a5a1f10deb2312795cc5dc157a76..ae08011006851493ad315f2490a4374877b2a02d 100644
--- a/src/main/java/net/minecraft/world/level/block/CactusBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/CactusBlock.java
@@ -118,9 +118,9 @@ public class CactusBlock extends Block {
     @Override
     public void entityInside(BlockState state, Level world, BlockPos pos, Entity entity) {
         if (!new io.papermc.paper.event.entity.EntityInsideBlockEvent(entity.getBukkitEntity(), org.bukkit.craftbukkit.block.CraftBlock.at(world, pos)).callEvent()) { return; } // Paper
-        CraftEventFactory.blockDamage = world.getWorld().getBlockAt(pos.getX(), pos.getY(), pos.getZ()); // CraftBukkit
+        CraftEventFactory.blockDamageRT.set(world.getWorld().getBlockAt(pos.getX(), pos.getY(), pos.getZ())); // CraftBukkit // Folia - region threading
         entity.hurt(DamageSource.CACTUS, 1.0F);
-        CraftEventFactory.blockDamage = null; // CraftBukkit
+        CraftEventFactory.blockDamageRT.set(null); // CraftBukkit // Folia - region threading
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/world/level/block/CampfireBlock.java b/src/main/java/net/minecraft/world/level/block/CampfireBlock.java
index a4c44cb59dee29cf227dbb51bfc1576d89dfb2e3..3d3f85e10c56dc95a0b6e576bd4b8d33a9daa8a3 100644
--- a/src/main/java/net/minecraft/world/level/block/CampfireBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/CampfireBlock.java
@@ -95,9 +95,9 @@ public class CampfireBlock extends BaseEntityBlock implements SimpleWaterloggedB
     public void entityInside(BlockState state, Level world, BlockPos pos, Entity entity) {
         if (!new io.papermc.paper.event.entity.EntityInsideBlockEvent(entity.getBukkitEntity(), org.bukkit.craftbukkit.block.CraftBlock.at(world, pos)).callEvent()) { return; } // Paper
         if ((Boolean) state.getValue(CampfireBlock.LIT) && entity instanceof LivingEntity && !EnchantmentHelper.hasFrostWalker((LivingEntity) entity)) {
-            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamage = CraftBlock.at(world, pos); // CraftBukkit
+            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamageRT.set(CraftBlock.at(world, pos)); // CraftBukkit // Folia - region threading
             entity.hurt(DamageSource.IN_FIRE, (float) this.fireDamage);
-            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamage = null; // CraftBukkit
+            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamageRT.set(null); // CraftBukkit // Folia - region threading
         }
 
         super.entityInside(state, world, pos, entity);
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 16504b8be08064e61b013fa943f692816612cbd0..076c6209725bac9268c19c7bfec7b5a94f2ea9a1 100644
--- a/src/main/java/net/minecraft/world/level/block/DaylightDetectorBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DaylightDetectorBlock.java
@@ -113,7 +113,7 @@ 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 8f55d0753fa26924235c943595f0d1a06a933a6f..a195d37847e3278d7721641b5db858913c0afe46 100644
--- a/src/main/java/net/minecraft/world/level/block/DispenserBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DispenserBlock.java
@@ -47,7 +47,7 @@ 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
 
     public static void registerBehavior(ItemLike provider, DispenseItemBehavior behavior) {
         DispenserBlock.DISPENSER_REGISTRY.put(provider.asItem(), behavior);
@@ -94,7 +94,7 @@ public class DispenserBlock extends BaseEntityBlock {
 
             if (idispensebehavior != DispenseItemBehavior.NOOP) {
                 if (!org.bukkit.craftbukkit.event.CraftEventFactory.handleBlockPreDispenseEvent(world, pos, itemstack, i)) return; // Paper - BlockPreDispenseEvent is called here
-                DispenserBlock.eventFired = false; // CraftBukkit - reset event status
+                DispenserBlock.eventFired.set(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 e234ae13fe9793db237adb6f6216fa32638cfc4f..9447bc16dcd7ecfa941081197d5e4c34f78c79d4 100644
--- a/src/main/java/net/minecraft/world/level/block/DoublePlantBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/DoublePlantBlock.java
@@ -95,7 +95,7 @@ public class DoublePlantBlock extends BushBlock {
 
     protected static void preventCreativeDropFromBottomPart(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/HoneyBlock.java b/src/main/java/net/minecraft/world/level/block/HoneyBlock.java
index 683f24251baf8ef3bef8f32ba83dc7f0e8ed7d70..b0352a9f05ad1ec49314d505dc99ed7b29ed09c3 100644
--- a/src/main/java/net/minecraft/world/level/block/HoneyBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/HoneyBlock.java
@@ -81,7 +81,7 @@ 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 da3b301a42a93c891d083a6e02d1be8ed35adf1d..f354981843868bf938be0b5ac1ef2ce39fb067ef 100644
--- a/src/main/java/net/minecraft/world/level/block/LightningRodBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/LightningRodBlock.java
@@ -112,7 +112,7 @@ 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/MagmaBlock.java b/src/main/java/net/minecraft/world/level/block/MagmaBlock.java
index d3540a4daaa8021ae009bfd4d9ef4f1172ab4c56..336a4797d114ccfad319086c68e3546bdf3f6fe1 100644
--- a/src/main/java/net/minecraft/world/level/block/MagmaBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/MagmaBlock.java
@@ -29,9 +29,9 @@ public class MagmaBlock extends Block {
     @Override
     public void stepOn(Level world, BlockPos pos, BlockState state, Entity entity) {
         if (!entity.isSteppingCarefully() && entity instanceof LivingEntity && !EnchantmentHelper.hasFrostWalker((LivingEntity) entity)) {
-            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamage = world.getWorld().getBlockAt(pos.getX(), pos.getY(), pos.getZ()); // CraftBukkit
+            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamageRT.set(world.getWorld().getBlockAt(pos.getX(), pos.getY(), pos.getZ())); // CraftBukkit // Folia - region threading
             entity.hurt(DamageSource.HOT_FLOOR, 1.0F);
-            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamage = null; // CraftBukkit
+            org.bukkit.craftbukkit.event.CraftEventFactory.blockDamageRT.set(null); // CraftBukkit // Folia - region threading
         }
 
         super.stepOn(world, pos, state, entity);
diff --git a/src/main/java/net/minecraft/world/level/block/PointedDripstoneBlock.java b/src/main/java/net/minecraft/world/level/block/PointedDripstoneBlock.java
index e78fdd317d59cfca6a28deb6e0bd02aabe91e930..c2cb07426d22ff0c14dfa24cc2ead785eaaf1903 100644
--- a/src/main/java/net/minecraft/world/level/block/PointedDripstoneBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/PointedDripstoneBlock.java
@@ -143,9 +143,9 @@ public class PointedDripstoneBlock extends Block implements Fallable, SimpleWate
     @Override
     public void fallOn(Level world, BlockState state, BlockPos pos, Entity entity, float fallDistance) {
         if (state.getValue(PointedDripstoneBlock.TIP_DIRECTION) == Direction.UP && state.getValue(PointedDripstoneBlock.THICKNESS) == DripstoneThickness.TIP) {
-            CraftEventFactory.blockDamage = CraftBlock.at(world, pos); // CraftBukkit
+            CraftEventFactory.blockDamageRT.set(CraftBlock.at(world, pos)); // CraftBukkit // Folia - region threading
             entity.causeFallDamage(fallDistance + 2.0F, 2.0F, DamageSource.STALAGMITE);
-            CraftEventFactory.blockDamage = null; // CraftBukkit
+            CraftEventFactory.blockDamageRT.set(null); // CraftBukkit // Folia - region threading
         } else {
             super.fallOn(world, state, pos, entity, fallDistance);
         }
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 5ea09cc455bd86beb450f0e0275d7c6c8da98084..1c23d52b77fea5f9817b482e2904083237ee58c4 100644
--- a/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
@@ -262,7 +262,7 @@ public class RedStoneWireBlock extends Block {
      * Note: Added 'source' argument so as to help determine direction of information flow
      */
     private void updateSurroundingRedstone(Level worldIn, BlockPos pos, BlockState state, BlockPos source) {
-        if (worldIn.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.EIGENCRAFT) {
+        if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.EIGENCRAFT) { // Folia - region threading
             turbo.updateSurroundingRedstone(worldIn, pos, state, source);
             return;
         }
@@ -286,7 +286,7 @@ public class RedStoneWireBlock extends Block {
         int k = worldIn.getBestNeighborSignal(pos1);
         this.shouldSignal = true;
 
-        if (worldIn.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA) {
+        if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA) { // Folia - region threading
             // This code is totally redundant to if statements just below the loop.
             if (k > 0 && k > j - 1) {
                 j = k;
@@ -300,7 +300,7 @@ public class RedStoneWireBlock extends Block {
         // redstone wire will be set to 'k'.  If 'k' is already 15, then nothing inside the
         // following loop can affect the power level of the wire.  Therefore, the loop is
         // skipped if k is already 15.
-        if (worldIn.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA || k < 15) {
+        if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA || k < 15) { // Folia - region threading
             for (Direction enumfacing : Direction.Plane.HORIZONTAL) {
                 BlockPos blockpos = pos1.relative(enumfacing);
                 boolean flag = blockpos.getX() != pos2.getX() || blockpos.getZ() != pos2.getZ();
@@ -319,7 +319,7 @@ public class RedStoneWireBlock extends Block {
             }
         }
 
-        if (worldIn.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA) {
+        if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA) { // Folia - region threading
             // The old code would decrement the wire value only by 1 at a time.
             if (l > j) {
                 j = l - 1;
@@ -455,7 +455,7 @@ public class RedStoneWireBlock extends Block {
     public void onPlace(BlockState state, Level world, BlockPos pos, BlockState oldState, boolean notify) {
         if (!oldState.is(state.getBlock()) && !world.isClientSide) {
             // Paper start - optimize redstone - replace call to updatePowerStrength
-            if (world.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) {
+            if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) { // Folia - region threading
                 world.getWireHandler().onWireAdded(pos); // Alternate Current
             } else {
                 this.updateSurroundingRedstone(world, pos, state, null); // vanilla/Eigencraft
@@ -488,7 +488,7 @@ public class RedStoneWireBlock extends Block {
                 }
 
                 // Paper start - optimize redstone - replace call to updatePowerStrength
-                if (world.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) {
+                if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) { // Folia - region threading
                     world.getWireHandler().onWireRemoved(pos, state); // Alternate Current
                 } else {
                     this.updateSurroundingRedstone(world, pos, state, null); // vanilla/Eigencraft
@@ -529,7 +529,7 @@ public class RedStoneWireBlock extends Block {
         if (!world.isClientSide) {
             // Paper start - optimize redstone (Alternate Current)
             // Alternate Current handles breaking of redstone wires in the WireHandler.
-            if (world.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) {
+            if (io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.VANILLA == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) { // Folia - region threading
                 world.getWireHandler().onWireUpdated(pos);
             } else
             // Paper end
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 da07fce0cf7c9fbdb57d2c59e431b59bf583bf50..16e46bb6205c3f7444e864c553e8072f0519746d 100644
--- a/src/main/java/net/minecraft/world/level/block/RedstoneTorchBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/RedstoneTorchBlock.java
@@ -73,10 +73,10 @@ public class RedstoneTorchBlock extends TorchBlock {
     public void tick(BlockState state, ServerLevel world, BlockPos pos, RandomSource random) {
         boolean flag = this.hasNeighborSignal(world, pos, state);
         // Paper start
-        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();
             }
         }
@@ -157,14 +157,14 @@ public class RedstoneTorchBlock extends TorchBlock {
 
     private static boolean isToggledTooFrequently(Level world, BlockPos pos, boolean addNew) {
         // Paper start
-        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
         }
 
 
         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;
@@ -185,12 +185,18 @@ public class RedstoneTorchBlock extends TorchBlock {
 
     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 901978a338f0f1b6f20ffb65aac59704bfa6f36a..01d8895fc04830d6f691852aaadf21d3ede75808 100644
--- a/src/main/java/net/minecraft/world/level/block/SaplingBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/SaplingBlock.java
@@ -52,18 +52,19 @@ 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.RegionisedWorldData 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) {
+                worldData.captureTreeGeneration = false; // Folia - region threading
+                if (worldData.capturedBlockStates.size() > 0) { // Folia - region threading
                     TreeType treeType = SaplingBlock.treeType;
                     SaplingBlock.treeType = null;
                     Location location = new Location(world.getWorld(), pos.getX(), pos.getY(), pos.getZ());
-                    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 af46c05a34292d271fd4a809398e6b299e10b12b..49a8d37b9c77dbc869c03e9f495efeeef606fa4a 100644
--- a/src/main/java/net/minecraft/world/level/block/SpreadingSnowyDirtBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/SpreadingSnowyDirtBlock.java
@@ -51,7 +51,7 @@ 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
+        if (this instanceof GrassBlock && world.paperConfig().tickRates.grassSpread != 1 && (world.paperConfig().tickRates.grassSpread < 1 || (io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick() + pos.hashCode()) % world.paperConfig().tickRates.grassSpread != 0)) { return; } // Paper // Folia - regionised ticking
         // Paper start
         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/SweetBerryBushBlock.java b/src/main/java/net/minecraft/world/level/block/SweetBerryBushBlock.java
index c926cd3ebb916115a608e86b389ffe7e15d48cd7..5375f79c6d5e05f4202a6363eaf50e6e6548a789 100644
--- a/src/main/java/net/minecraft/world/level/block/SweetBerryBushBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/SweetBerryBushBlock.java
@@ -86,9 +86,9 @@ public class SweetBerryBushBlock extends BushBlock implements BonemealableBlock
                 double d1 = Math.abs(entity.getZ() - entity.zOld);
 
                 if (d0 >= 0.003000000026077032D || d1 >= 0.003000000026077032D) {
-                    CraftEventFactory.blockDamage = CraftBlock.at(world, pos); // CraftBukkit
+                    CraftEventFactory.blockDamageRT.set(CraftBlock.at(world, pos)); // CraftBukkit // Folia - region threading
                     entity.hurt(DamageSource.SWEET_BERRY_BUSH, 1.0F);
-                    CraftEventFactory.blockDamage = null; // CraftBukkit
+                    CraftEventFactory.blockDamageRT.set(null); // CraftBukkit // Folia - region threading
                 }
             }
 
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 b91effe91dad2e1aeea0ea31140f7432833b343f..46979b4ee8c24b499577aa64167c759664148240 100644
--- a/src/main/java/net/minecraft/world/level/block/WitherSkullBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/WitherSkullBlock.java
@@ -53,7 +53,7 @@ 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 928625b5ab054ffa412be8a438f58291cc7a3cc0..bbc051be1c3a2697e33cc316e328760b838af243 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
@@ -202,7 +202,7 @@ 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 58986bc0677c5ea1ad54d7d6d4efa5c2ea233aea..ac1f6d5c78c1970b3242c017031679fb9a906fb0 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 IGNORE_TILE_UPDATES = false; // Paper
+    static final ThreadLocal<Boolean> IGNORE_TILE_UPDATES = ThreadLocal.withInitial(() -> Boolean.FALSE); // Paper // Folia - region threading
 
     public Timing tickTimer = MinecraftTimings.getTileEntityTimings(this); // Paper
     // CraftBukkit start - data containers
@@ -42,6 +42,12 @@ 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();
@@ -163,7 +169,7 @@ public abstract class BlockEntity {
 
     public void setChanged() {
         if (this.level != null) {
-            if (IGNORE_TILE_UPDATES) return; // Paper
+            if (IGNORE_TILE_UPDATES.get()) return; // Paper // 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 55006724ccec9f3de828ec18693728e9741ff65f..9e806ba83240916d422c4a736a9cfd61e73108e4 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
@@ -54,7 +54,7 @@ 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 = 64;
 
@@ -171,11 +171,10 @@ 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/ConduitBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/ConduitBlockEntity.java
index 05eab04e4aec4151018f25b59f92ddbbb4c09f87..2a6e3eb2ec74e8b1a356b5a62ec5f8521da00380 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
@@ -88,7 +88,7 @@ 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) {
@@ -106,7 +106,7 @@ 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) {
@@ -236,11 +236,11 @@ public class ConduitBlockEntity extends BlockEntity {
 
         if (blockEntity.destroyTarget != null) {
             // CraftBukkit start
-            CraftEventFactory.blockDamage = CraftBlock.at(world, pos);
+            CraftEventFactory.blockDamageRT.set(CraftBlock.at(world, pos)); // Folia - region threading
             if (blockEntity.destroyTarget.hurt(DamageSource.MAGIC, 4.0F)) {
                 world.playSound((Player) null, blockEntity.destroyTarget.getX(), blockEntity.destroyTarget.getY(), blockEntity.destroyTarget.getZ(), SoundEvents.CONDUIT_ATTACK_TARGET, SoundSource.BLOCKS, 1.0F, 1.0F);
             }
-            CraftEventFactory.blockDamage = null;
+            CraftEventFactory.blockDamageRT.set(null); // Folia - region threading
             // CraftBukkit end
         }
 
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 ccad692aba2ed77259f6814d88f01b91ed9d229b..955f6560f4c6032d375927987c9bb62561ed5034 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
@@ -189,12 +189,11 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
         return false;
     }
     // Paper start - Optimize Hoppers
-    private static boolean skipPullModeEventFire = false;
-    private static boolean skipPushModeEventFire = false;
-    public static boolean skipHopperEvents = false;
+    // Folia - region threading - moved to RegionisedWorldData
 
     private static boolean hopperPush(Level level, BlockPos pos, Container destination, Direction enumdirection, HopperBlockEntity hopper) {
-        skipPushModeEventFire = skipHopperEvents;
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = level.getCurrentWorldData(); // Folia - region threading
+        worldData.skipPushModeEventFire = worldData.skipHopperEvents; // Folia - region threading
         boolean foundItem = false;
         for (int i = 0; i < hopper.getContainerSize(); ++i) {
             ItemStack item = hopper.getItem(i);
@@ -209,7 +208,7 @@ 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
                     itemstack = callPushMoveEvent(destination, itemstack, hopper);
                     if (itemstack == null) { // cancelled
                         origItemStack.setCount(origCount);
@@ -238,12 +237,13 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     private static boolean hopperPull(Level level, Hopper ihopper, Container iinventory, ItemStack origItemStack, int i) {
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = level.getCurrentWorldData(); // Folia - region threading
         ItemStack itemstack = origItemStack;
         final int origCount = origItemStack.getCount();
         final int moved = Math.min(level.spigotConfig.hopperAmount, origCount);
         itemstack.setCount(moved);
 
-        if (!skipPullModeEventFire) {
+        if (!worldData.skipPullModeEventFire) { // Folia - region threading
             itemstack = callPullMoveEvent(ihopper, iinventory, itemstack);
             if (itemstack == null) { // cancelled
                 origItemStack.setCount(origCount);
@@ -262,9 +262,9 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             if (!origItemStack.isEmpty()) {
                 origItemStack.setCount(origCount - moved + remaining);
             }
-            IGNORE_TILE_UPDATES = true;
+            IGNORE_TILE_UPDATES.set(true); // Folia - region threading
             iinventory.setItem(i, origItemStack);
-            IGNORE_TILE_UPDATES = false;
+            IGNORE_TILE_UPDATES.set(false); // Folia - region threading
             iinventory.setChanged();
             return true;
         }
@@ -278,12 +278,13 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     private static ItemStack callPushMoveEvent(Container iinventory, ItemStack itemstack, HopperBlockEntity hopper) {
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData(); // Folia - region threading
         Inventory destinationInventory = getInventory(iinventory);
         InventoryMoveItemEvent event = new InventoryMoveItemEvent(hopper.getOwner(false).getInventory(),
             CraftItemStack.asCraftMirror(itemstack), destinationInventory, true);
         boolean result = event.callEvent();
         if (!event.calledGetItem && !event.calledSetItem) {
-            skipPushModeEventFire = true;
+            worldData.skipPushModeEventFire = true; // Folia - region threading
         }
         if (!result) {
             cooldownHopper(hopper);
@@ -298,6 +299,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     }
 
     private static ItemStack callPullMoveEvent(Hopper hopper, Container iinventory, ItemStack itemstack) {
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData(); // Folia - region threading
         Inventory sourceInventory = getInventory(iinventory);
         Inventory destination = getInventory(hopper);
 
@@ -306,7 +308,7 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
             CraftItemStack.asCraftMirror(itemstack), destination, false);
         boolean result = event.callEvent();
         if (!event.calledGetItem && !event.calledSetItem) {
-            skipPullModeEventFire = true;
+            worldData.skipPullModeEventFire = true; // Folia - region threading
         }
         if (!result) {
             cooldownHopper(hopper);
@@ -447,13 +449,14 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
     // Paper end
 
     public static boolean suckInItems(Level world, Hopper hopper) {
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = io.papermc.paper.threadedregions.TickRegionScheduler.getCurrentRegionisedWorldData(); // Folia - region threading
         Container iinventory = HopperBlockEntity.getSourceContainer(world, hopper);
 
         if (iinventory != null) {
             Direction enumdirection = Direction.DOWN;
 
             // Paper start - optimize hoppers and remove streams
-            skipPullModeEventFire = skipHopperEvents;
+            worldData.skipPullModeEventFire = worldData.skipHopperEvents; // Folia - region threading
             return !HopperBlockEntity.isEmptyContainer(iinventory, enumdirection) && anyMatch(iinventory, enumdirection, (item, i) -> {
                 // Logic copied from below to avoid extra getItem calls
                 if (!item.isEmpty() && canTakeItemFromContainer(iinventory, item, i, enumdirection)) {
@@ -592,9 +595,9 @@ public class HopperBlockEntity extends RandomizableContainerBlockEntity implemen
                     stack = stack.split(to.getMaxStackSize());
                 }
                 // Spigot end
-                IGNORE_TILE_UPDATES = true; // Paper
+                IGNORE_TILE_UPDATES.set(true); // Paper // Folia - region threading
                 to.setItem(slot, stack);
-                IGNORE_TILE_UPDATES = false; // Paper
+                IGNORE_TILE_UPDATES.set(false); // Paper // Folia - region threading
                 stack = leftover; // Paper
                 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 163e63e3c538c7c1c75ed634896db9d8c00416f3..740cb2858a3f78298895a463fb0fac9e88a9a4a0 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
@@ -86,9 +86,9 @@ public class SculkCatalystBlockEntity extends BlockEntity implements GameEventLi
     }
 
     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.sculkSpreader.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 f80545f80948db27d1fbde77d0505c916eb504ed..3b656e7d5e8b75f8f415d5f43ed5c91da963731b 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);
     }
@@ -128,7 +131,7 @@ 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() {
@@ -176,8 +179,112 @@ 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.RegionisedServer.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;
+        }
+
+        // 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
+            entity.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
+            entity.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.getRootVehicle(), blockEntity);
+                return;
+            }
+            // Folia end - region threading
             ServerLevel worldserver = (ServerLevel) world;
 
             blockEntity.teleportCooldown = 100;
@@ -281,6 +388,125 @@ 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(vec3d.x + 0.5D, 75.0D, 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.RegionisedServer.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/piston/PistonMovingBlockEntity.java b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
index 221c5d080d55326e458c1182823d6b49224ef498..29a27534e6c97b262229b51e4ea0345502020647 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
@@ -144,8 +144,8 @@ 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.RegionisedServer.getCurrentTick() + 10); // Folia - region threading
+                                entity.activatedImmunityTick = Math.max(entity.activatedImmunityTick, io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick() + 10); // Folia - region threading
                                 // Paper end
                                 break;
                             }
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 7a12a4da4864306ec6589ca81368e84718825047..e3ef5ccad7f8a8138b1372f419680409ddeab291 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
-    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
 
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 7e9c388179c75a233d9b179ea1e00428ac65ee99..df83966cb2be368aaee95f3b8563e01ab807d816 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
@@ -308,7 +308,7 @@ public abstract class ChunkGenerator {
                         return Pair.of(placement.getLocatePos(pos), holder);
                     }
 
-                    ChunkAccess ichunkaccess = world.getChunk(pos.x, pos.z, ChunkStatus.STRUCTURE_STARTS);
+                    ChunkAccess ichunkaccess = world.syncLoadNonFull(pos.x, pos.z, ChunkStatus.STRUCTURE_STARTS); // Folia - region threading
 
                     structurestart = structureAccessor.getStartForStructure(SectionPos.bottomOf(ichunkaccess), (Structure) holder.value(), ichunkaccess);
                 } while (structurestart == null);
@@ -319,7 +319,7 @@ 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 e776eb8afef978938da084f9ae29d611181b43fe..d270f6b5937e167f18c3f358c99a9f6f3cde9c7a 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -61,6 +61,13 @@ 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;
@@ -233,51 +240,15 @@ public class LevelChunk extends ChunkAccess {
     }
     // Paper end
     // Paper start - optimise checkDespawn
-    private boolean playerGeneralAreaCacheSet;
-    private com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> playerGeneralAreaCache;
-
-    public com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> getPlayerGeneralAreaCache() {
-        if (!this.playerGeneralAreaCacheSet) {
-            this.updateGeneralAreaCache();
-        }
-        return this.playerGeneralAreaCache;
-    }
-
-    public void updateGeneralAreaCache() {
-        this.updateGeneralAreaCache(((ServerLevel)this.level).getChunkSource().chunkMap.playerGeneralAreaMap.getObjectsInRange(this.coordinateKey));
-    }
-
-    public void removeGeneralAreaCache() {
-        this.playerGeneralAreaCacheSet = false;
-        this.playerGeneralAreaCache = null;
-    }
-
-    public void updateGeneralAreaCache(com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> value) {
-        this.playerGeneralAreaCacheSet = true;
-        this.playerGeneralAreaCache = value;
-    }
-
+    // Folia - region threading
     public net.minecraft.server.level.ServerPlayer findNearestPlayer(double sourceX, double sourceY, double sourceZ,
                                                                      double maxRange, java.util.function.Predicate<Entity> predicate) {
-        if (!this.playerGeneralAreaCacheSet) {
-            this.updateGeneralAreaCache();
-        }
-
-        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> nearby = this.playerGeneralAreaCache;
-
-        if (nearby == null) {
-            return null;
-        }
-
-        Object[] backingSet = nearby.getBackingSet();
+        // Folia start - region threading
         double closestDistance = maxRange < 0.0 ? Double.MAX_VALUE : maxRange * maxRange;
         net.minecraft.server.level.ServerPlayer closest = null;
-        for (int i = 0, len = backingSet.length; i < len; ++i) {
-            Object _player = backingSet[i];
-            if (!(_player instanceof net.minecraft.server.level.ServerPlayer)) {
-                continue;
-            }
-            net.minecraft.server.level.ServerPlayer player = (net.minecraft.server.level.ServerPlayer)_player;
+        java.util.List<net.minecraft.server.level.ServerPlayer> nearby = this.level.getLocalPlayers();
+        for (int i = 0, len = nearby.size(); i < len; ++i) {
+            net.minecraft.server.level.ServerPlayer player = nearby.get(i);
 
             double distance = player.distanceToSqr(sourceX, sourceY, sourceZ);
             if (distance < closestDistance && predicate.test(player)) {
@@ -285,31 +256,17 @@ public class LevelChunk extends ChunkAccess {
                 closestDistance = distance;
             }
         }
-
         return closest;
+        // Folia end - region threading
     }
 
     public void getNearestPlayers(double sourceX, double sourceY, double sourceZ, java.util.function.Predicate<Entity> predicate,
                                   double range, java.util.List<net.minecraft.server.level.ServerPlayer> ret) {
-        if (!this.playerGeneralAreaCacheSet) {
-            this.updateGeneralAreaCache();
-        }
-
-        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> nearby = this.playerGeneralAreaCache;
-
-        if (nearby == null) {
-            return;
-        }
-
+        // Folia start - region threading
         double rangeSquared = range * range;
-
-        Object[] backingSet = nearby.getBackingSet();
-        for (int i = 0, len = backingSet.length; i < len; ++i) {
-            Object _player = backingSet[i];
-            if (!(_player instanceof net.minecraft.server.level.ServerPlayer)) {
-                continue;
-            }
-            net.minecraft.server.level.ServerPlayer player = (net.minecraft.server.level.ServerPlayer)_player;
+        java.util.List<net.minecraft.server.level.ServerPlayer> nearby = this.level.getLocalPlayers();
+        for (int i = 0, len = nearby.size(); i < len; ++i) {
+            net.minecraft.server.level.ServerPlayer player = nearby.get(i);
 
             if (range >= 0.0) {
                 double distanceSquared = player.distanceToSqr(sourceX, sourceY, sourceZ);
@@ -322,6 +279,7 @@ public class LevelChunk extends ChunkAccess {
                 ret.add(player);
             }
         }
+        // Folia end - region threading
     }
     // Paper end - optimise checkDespawn
 
@@ -557,7 +515,7 @@ 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);
                     }
 
@@ -604,7 +562,7 @@ public class LevelChunk extends ChunkAccess {
     @Nullable
     public BlockEntity getBlockEntity(BlockPos pos, LevelChunk.EntityCreationType creationType) {
         // CraftBukkit start
-        BlockEntity tileentity = level.capturedTileEntities.get(pos);
+        BlockEntity tileentity = level.getCurrentWorldData().capturedTileEntities.get(pos); // Folia - region threading
         if (tileentity == null) {
             tileentity = (BlockEntity) this.blockEntities.get(pos);
         }
@@ -889,13 +847,13 @@ 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(this.bukkitChunk));
@@ -944,7 +902,7 @@ 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;
         }
@@ -1213,6 +1171,13 @@ 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();
@@ -1249,6 +1214,13 @@ 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 256642f2e2aa66f7e8c00cae91a75060a8817c9c..9fb91e3648db3ad79bb6d1fe79894a13ddc07cbb 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
@@ -687,7 +687,7 @@ 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 e9eb32469a5c03f7a3677ef50fd4541c1ed662ad..3ff5e74a2aae72eebe6730a4df15b17c1c8ff43a 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
@@ -168,6 +168,7 @@ public class EndDragonFight {
         if (!this.dragonEvent.getPlayers().isEmpty()) {
             this.level.getChunkSource().addRegionTicket(TicketType.DRAGON, new ChunkPos(0, 0), 9, Unit.INSTANCE);
             boolean bl = this.isArenaLoaded();
+            if (!bl) { return; }// Folia - region threading - don't tick if we don't own the entire region
             if (this.needsStateScanning && bl) {
                 this.scanState();
                 this.needsStateScanning = false;
@@ -214,6 +215,12 @@ 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;
         } else {
@@ -324,8 +331,8 @@ public class EndDragonFight {
     private boolean isArenaLoaded() {
         for(int i = -8; i <= 8; ++i) {
             for(int j = 8; j <= 8; ++j) {
-                ChunkAccess chunkAccess = this.level.getChunk(i, j, ChunkStatus.FULL, false);
-                if (!(chunkAccess instanceof LevelChunk)) {
+                ChunkAccess chunkAccess = this.level.getChunkIfLoaded(i, j); // Folia - region threading
+                if (!(chunkAccess instanceof LevelChunk) || !io.papermc.paper.util.TickThread.isTickThreadFor(this.level, i, j, this.level.regioniser.regionSectionChunkSize)) { // Folia - region threading
                     return false;
                 }
 
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 a908652f1ebb426d265ef614746f70cd1e538268..b2a9cd719c4968a1cde8f0b30f46f01d5872fbc9 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.RegionisedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
 
             // Paper start - Patrol settings
             // 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 1c3718d9244513d9fc795dceb564a81375734557..f445e1db1538fb9eda4b2f81f62748dc57fda24a 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/PhantomSpawner.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/PhantomSpawner.java
@@ -24,7 +24,7 @@ import net.minecraft.world.level.material.FluidState;
 
 public class PhantomSpawner implements CustomSpawner {
 
-    private int nextTick;
+    //private int nextTick; // Folia - region threading
 
     public PhantomSpawner() {}
 
@@ -42,20 +42,22 @@ public class PhantomSpawner implements CustomSpawner {
             // Paper end
             RandomSource randomsource = world.random;
 
-            --this.nextTick;
-            if (this.nextTick > 0) {
+            io.papermc.paper.threadedregions.RegionisedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+
+            --worldData.phantomSpawnerNextTick; // Folia - region threading
+            if (worldData.phantomSpawnerNextTick > 0) { // Folia - region threading
                 return 0;
             } else {
                 // Paper start
                 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
                 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()) {
                         Player entityhuman = (Player) iterator.next();
diff --git a/src/main/java/net/minecraft/world/level/levelgen/structure/StructureCheck.java b/src/main/java/net/minecraft/world/level/levelgen/structure/StructureCheck.java
index 4761aa772bc34dd66547dd4dd561c2e04c3229ad..ac4648773c9d6316db4915d515991219589fa473 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/structure/StructureCheck.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/structure/StructureCheck.java
@@ -51,8 +51,101 @@ public class StructureCheck {
     private final BiomeSource biomeSource;
     private final long seed;
     private final DataFixer fixerUpper;
-    private final Long2ObjectMap<Object2IntMap<Structure>> loadedChunks = new Long2ObjectOpenHashMap<>();
-    private final Map<Structure, Long2BooleanMap> featureChecks = new HashMap<>();
+    // Foila start - synchronise this class
+    // additionally, make sure to purge entries from the maps so it does not leak memory
+    private static final int CHUNK_TOTAL_LIMIT = 50 * (2 * 100 + 1) * (2 * 100 + 1); // cache 50 structure lookups
+    private static final int PER_FEATURE_CHECK_LIMIT = 50 * (2 * 100 + 1) * (2 * 100 + 1); // cache 50 structure lookups
+
+    private final SynchronisedLong2ObjectMap<Object2IntMap<Structure>> loadedChunksSafe = new SynchronisedLong2ObjectMap<>(CHUNK_TOTAL_LIMIT);
+    private final java.util.concurrent.ConcurrentHashMap<Structure, SynchronisedLong2BooleanMap> featureChecksSafe = new java.util.concurrent.ConcurrentHashMap<>();
+
+    private static final class SynchronisedLong2ObjectMap<V> {
+        private final it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap<V> map = new it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap<>();
+        private final int limit;
+
+        public SynchronisedLong2ObjectMap(final int limit) {
+            this.limit = limit;
+        }
+
+        // must hold lock on map
+        private void purgeEntries() {
+            while (this.map.size() > this.limit) {
+                this.map.removeLast();
+            }
+        }
+
+        public V get(final long key) {
+            synchronized (this.map) {
+                return this.map.getAndMoveToFirst(key);
+            }
+        }
+
+        public V put(final long key, final V value) {
+            synchronized (this.map) {
+                final V ret = this.map.putAndMoveToFirst(key, value);
+                this.purgeEntries();
+                return ret;
+            }
+        }
+
+        public V compute(final long key, final java.util.function.BiFunction<? super Long, ? super V, ? extends V> remappingFunction) {
+            synchronized (this.map) {
+                // first, compute the value - if one is added, it will be at the last entry
+                this.map.compute(key, remappingFunction);
+                // move the entry to first, just in case it was added at last
+                final V ret = this.map.getAndMoveToFirst(key);
+                // now purge the last entries
+                this.purgeEntries();
+
+                return ret;
+            }
+        }
+    }
+
+    private static final class SynchronisedLong2BooleanMap {
+        private final it.unimi.dsi.fastutil.longs.Long2BooleanLinkedOpenHashMap map = new it.unimi.dsi.fastutil.longs.Long2BooleanLinkedOpenHashMap();
+        private final int limit;
+
+        public SynchronisedLong2BooleanMap(final int limit) {
+            this.limit = limit;
+        }
+
+        // must hold lock on map
+        private void purgeEntries() {
+            while (this.map.size() > this.limit) {
+                this.map.removeLastBoolean();
+            }
+        }
+
+        public boolean remove(final long key) {
+            synchronized (this.map) {
+                return this.map.remove(key);
+            }
+        }
+
+        // note:
+        public boolean getOrCompute(final long key, final it.unimi.dsi.fastutil.longs.Long2BooleanFunction ifAbsent) {
+            synchronized (this.map) {
+                if (this.map.containsKey(key)) {
+                    return this.map.getAndMoveToFirst(key);
+                }
+            }
+
+            final boolean put = ifAbsent.get(key);
+
+            synchronized (this.map) {
+                if (this.map.containsKey(key)) {
+                    return this.map.getAndMoveToFirst(key);
+                }
+                this.map.putAndMoveToFirst(key, put);
+
+                this.purgeEntries();
+
+                return put;
+            }
+        }
+    }
+    // Foila end - synchronise this class
 
     public StructureCheck(ChunkScanAccess chunkIoWorker, RegistryAccess registryManager, StructureTemplateManager structureTemplateManager, ResourceKey<net.minecraft.world.level.dimension.LevelStem> worldKey, ChunkGenerator chunkGenerator, RandomState noiseConfig, LevelHeightAccessor world, BiomeSource biomeSource, long seed, DataFixer dataFixer) { // Paper - fix missing CB diff
         this.storageAccess = chunkIoWorker;
@@ -71,7 +164,7 @@ public class StructureCheck {
 
     public StructureCheckResult checkStart(ChunkPos pos, Structure type, boolean skipReferencedStructures) {
         long l = pos.toLong();
-        Object2IntMap<Structure> object2IntMap = this.loadedChunks.get(l);
+        Object2IntMap<Structure> object2IntMap = this.loadedChunksSafe.get(l); // Folia - region threading
         if (object2IntMap != null) {
             return this.checkStructureInfo(object2IntMap, type, skipReferencedStructures);
         } else {
@@ -79,9 +172,9 @@ public class StructureCheck {
             if (structureCheckResult != null) {
                 return structureCheckResult;
             } else {
-                boolean bl = this.featureChecks.computeIfAbsent(type, (structure2) -> {
-                    return new Long2BooleanOpenHashMap();
-                }).computeIfAbsent(l, (chunkPos) -> {
+                boolean bl = this.featureChecksSafe.computeIfAbsent(type, (structure2) -> { // Folia - region threading
+                    return new SynchronisedLong2BooleanMap(PER_FEATURE_CHECK_LIMIT); // Folia - region threading
+                }).getOrCompute(l, (chunkPos) -> { // Folia - region threading
                     return this.canCreateStructure(pos, type);
                 });
                 return !bl ? StructureCheckResult.START_NOT_PRESENT : StructureCheckResult.CHUNK_LOAD_NEEDED;
@@ -194,17 +287,26 @@ public class StructureCheck {
     }
 
     private void storeFullResults(long pos, Object2IntMap<Structure> referencesByStructure) {
-        this.loadedChunks.put(pos, deduplicateEmptyMap(referencesByStructure));
-        this.featureChecks.values().forEach((generationPossibilityByChunkPos) -> {
-            generationPossibilityByChunkPos.remove(pos);
-        });
+        // Folia start - region threading - make access mt-safe
+        this.loadedChunksSafe.put(pos, deduplicateEmptyMap(referencesByStructure));
+        // once we insert into loadedChunks, we don't really need to be very careful about removing everything
+        // from this map, as everything that checks this map uses loadedChunks first
+        // so, one way or another it's a race condition that doesn't matter
+        for (SynchronisedLong2BooleanMap value : this.featureChecksSafe.values()) {
+            value.remove(pos);
+        }
+        // Folia end - region threading - make access mt-safe
     }
 
     public void incrementReference(ChunkPos pos, Structure structure) {
-        this.loadedChunks.compute(pos.toLong(), (posx, referencesByStructure) -> {
-            if (referencesByStructure == null || referencesByStructure.isEmpty()) {
+        this.loadedChunksSafe.compute(pos.toLong(), (posx, referencesByStructure) -> { // Folia start - region threading
+            // make this COW so that we do not mutate state that may be currently in use
+            if (referencesByStructure == null) {
                 referencesByStructure = new Object2IntOpenHashMap<>();
+            } else {
+                referencesByStructure = referencesByStructure instanceof Object2IntOpenHashMap<Structure> fastClone ? fastClone.clone() : new Object2IntOpenHashMap<>(referencesByStructure);
             }
+            // Folia end - region threading
 
             referencesByStructure.computeInt(structure, (feature, references) -> {
                 return references == null ? 1 : references + 1;
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 6570e0b61d7602c57c61398ddce50418d0719ff2..bcee13beed247f7830ee85d099c367dbfd1ea51d 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
@@ -26,14 +26,14 @@ 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;
 
     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;
     }
 
@@ -101,7 +101,7 @@ public final class StructureStart {
             compoundTag.putString("id", context.registryAccess().registryOrThrow(Registries.STRUCTURE).getKey(this.structure).toString());
             compoundTag.putInt("ChunkX", chunkPos.x);
             compoundTag.putInt("ChunkZ", chunkPos.z);
-            compoundTag.putInt("references", this.references);
+            compoundTag.putInt("references", this.references.get()); // Folia - region threading
             compoundTag.put("Children", this.pieceContainer.save(context));
             return compoundTag;
         } else {
@@ -119,15 +119,29 @@ 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 92d13c9f1ec1e5ff72c1d68f924a8d1c86c91565..3f224315f1e0a8f69e9d84d27fd7dbe45ea75667 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 b1c594dc6a6b8a6c737b99272acab9e7dbd0ed63..7c1768452fa0f7278ccc84470ef0965a3f96b0df 100644
--- a/src/main/java/net/minecraft/world/level/redstone/CollectingNeighborUpdater.java
+++ b/src/main/java/net/minecraft/world/level/redstone/CollectingNeighborUpdater.java
@@ -46,6 +46,7 @@ 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 c8cdcf40e45f5c6270f9b124f0333643266e2858..b370ba924b03cc0a36666ee6ed26be06a6affaa7 100644
--- a/src/main/java/net/minecraft/world/level/saveddata/SavedData.java
+++ b/src/main/java/net/minecraft/world/level/saveddata/SavedData.java
@@ -10,7 +10,7 @@ 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);
 
@@ -28,6 +28,7 @@ public abstract class SavedData {
 
     public void save(File file) {
         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()));
             compoundTag.putInt("DataVersion", SharedConstants.getCurrentVersion().getWorldVersion());
@@ -38,7 +39,7 @@ public abstract class SavedData {
                 LOGGER.error("Could not save data {}", this, var4);
             }
 
-            this.setDirty(false);
+            // Folia - make map data thread-safe - move before save, so that any changes after are not lost
         }
     }
 }
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 9b2948b5150c8f039ca667a50765109721b93947..1b76e4edce628f2b25815e28cd4cb7504a83a00f 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
@@ -27,17 +27,21 @@ public class MapIndex extends SavedData {
 
     @Override
     public CompoundTag save(CompoundTag nbt) {
+        synchronized (this.usedAuxIds) { // Folia - make map data thread-safe
         for(Object2IntMap.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 b2845ed8d28627178589da3d2224cd9edd29c31e..5121569f389ee4a50273432a9a272a936542fa12 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
@@ -185,7 +185,7 @@ 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;
 
@@ -242,7 +242,7 @@ 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);
@@ -253,11 +253,12 @@ 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, (int) 0, (int) 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);
 
@@ -368,7 +369,7 @@ 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);
             }
@@ -427,14 +428,14 @@ 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()) {
@@ -442,15 +443,16 @@ 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) {
@@ -462,7 +464,7 @@ 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;
@@ -471,7 +473,7 @@ 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;
@@ -492,7 +494,7 @@ 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()) {
@@ -514,12 +516,12 @@ 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) {
@@ -530,12 +532,12 @@ 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;
@@ -570,7 +572,7 @@ 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;
     }
 
@@ -696,11 +698,13 @@ 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 2da78bc43af715fe399eac1d83b3bf6e8fb8afac..433a9302f496a297172c02f3fe0404174cc7a8f1 100644
--- a/src/main/java/net/minecraft/world/level/storage/DimensionDataStorage.java
+++ b/src/main/java/net/minecraft/world/level/storage/DimensionDataStorage.java
@@ -36,6 +36,7 @@ public class DimensionDataStorage {
     }
 
     public <T extends SavedData> T computeIfAbsent(Function<CompoundTag, T> readFunction, Supplier<T> supplier, String id) {
+        synchronized (this.cache) { // Folia - make map data thread-safe
         T savedData = this.get(readFunction, id);
         if (savedData != null) {
             return savedData;
@@ -44,10 +45,12 @@ public class DimensionDataStorage {
             this.set(id, savedData2);
             return savedData2;
         }
+        } // Folia - make map data thread-safe
     }
 
     @Nullable
     public <T extends SavedData> T get(Function<CompoundTag, T> readFunction, 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(readFunction, id);
@@ -55,6 +58,7 @@ public class DimensionDataStorage {
         }
 
         return (T)savedData;
+        } // Folia - make map data thread-safe
     }
 
     @Nullable
@@ -73,7 +77,9 @@ public class DimensionDataStorage {
     }
 
     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, int dataVersion) 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 ac807277a6b26d140ea9873d17c7aa4fb5fe37b2..e13d8700593f1f486cfc5c96ac25894202c07b71 100644
--- a/src/main/java/net/minecraft/world/ticks/LevelChunkTicks.java
+++ b/src/main/java/net/minecraft/world/ticks/LevelChunkTicks.java
@@ -37,6 +37,21 @@ 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 7f1ac2cb29eb84833c0895442d611dfa0504527e..c79cfebc65fd04994735dabcf5bb6e6cc714aca8 100644
--- a/src/main/java/net/minecraft/world/ticks/LevelTicks.java
+++ b/src/main/java/net/minecraft/world/ticks/LevelTicks.java
@@ -42,13 +42,70 @@ 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;
     }
@@ -61,7 +118,17 @@ 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.RegionisedWorldData worldData = world.getCurrentWorldData();
+                (isBlock ? worldData.getBlockLevelTicks() : worldData.getFluidLevelTicks()).updateContainerScheduling((ScheduledTick)tick);
+            }
+        });
+        // Folia end - region threading
     }
 
     public void removeContainer(ChunkPos pos) {
@@ -76,6 +143,7 @@ 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 2ea3778ee1348e5d06b15a2c5dc5d9bd4136dbe3..c4c2a393ee2d5fbcdbf3abb4a49f1bfae2d2c618 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -879,6 +879,9 @@ 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.RegionisedServer.ensureGlobalTickThread("May not dispatch server commands async");
+        // Folia end - region threading
         if (sender instanceof Conversable) {
             Conversable conversable = (Conversable) sender;
 
@@ -898,12 +901,44 @@ 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 console) {
+            io.papermc.paper.threadedregions.RegionisedServer.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) {
         Validate.notNull(sender, "Sender cannot be null");
         Validate.notNull(commandLine, "CommandLine cannot be null");
         org.spigotmc.AsyncCatcher.catchOp("command dispatch"); // Spigot
 
+        // 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 console) {
+            io.papermc.paper.threadedregions.RegionisedServer.ensureGlobalTickThread("Dispatching command async");
+        } else {
+            // huh?
+            throw new UnsupportedOperationException("Dispatching command for " + sender);
+        }
+        // Folia end - region threading
+
         // Paper Start
         if (!org.spigotmc.AsyncCatcher.shuttingDown && !Bukkit.isPrimaryThread()) {
             final CommandSender fSender = sender;
@@ -2913,7 +2948,7 @@ public final class CraftServer implements Server {
 
     @Override
     public int getCurrentTick() {
-        return net.minecraft.server.MinecraftServer.currentTick;
+        return (int)io.papermc.paper.threadedregions.RegionisedServer.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 d33476ffa49d7f6388bb227f8a57cf115a74698f..ddb59118551449b4c8855cdeaabedb08af148fff 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -180,7 +180,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public int getTickableTileEntityCount() {
-        return world.getTotalTileEntityTickers();
+        throw new UnsupportedOperationException(); // Folia - region threading - TODO fix this?
     }
 
     @Override
@@ -788,13 +788,14 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public boolean generateTree(Location loc, TreeType type, BlockChangeDelegate delegate) {
-        world.captureTreeGeneration = true;
-        world.captureBlockStates = true;
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = world.getCurrentWorldData(); // Folia - region threading
+        worldData.captureTreeGeneration = true; // Folia - region threading
+        worldData.captureBlockStates = true; // Folia - region threading
         boolean grownTree = this.generateTree(loc, type);
-        world.captureBlockStates = false;
-        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 : 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();
@@ -802,10 +803,10 @@ 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);
             }
-            world.capturedBlockStates.clear();
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             return true;
         } else {
-            world.capturedBlockStates.clear();
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             return false;
         }
     }
@@ -878,7 +879,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
 
     @Override
     public long getGameTime() {
-        return world.levelData.getGameTime();
+        return this.getHandle().getGameTime(); // Folia - region threading
     }
 
     @Override
@@ -1853,7 +1854,7 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         if (!(entity instanceof CraftEntity craftEntity) || entity.getWorld() != this || sound == null || category == null) return;
 
         ClientboundSoundEntityPacket packet = new ClientboundSoundEntityPacket(BuiltInRegistries.SOUND_EVENT.wrapAsHolder(CraftSound.getSoundEffect(sound)), net.minecraft.sounds.SoundSource.valueOf(category.name()), craftEntity.getHandle(), volume, pitch, this.getHandle().getRandom().nextLong());
-        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);
         }
@@ -2356,7 +2357,7 @@ 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.RegionisedServer.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) addTicket(x, z); // Paper
                 ret.complete(chunk == null ? null : chunk.getBukkitChunk());
diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
index 350cbf64c17938021002d5fd67176c44b398231e..e54713a530e18344a7c7d1c400147fc33d64967f 100644
--- a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+++ b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
@@ -568,16 +568,17 @@ public class CraftBlock implements Block {
         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.RegionisedWorldData 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) {
+        if (worldData.capturedBlockStates.size() > 0) { // Folia - region threading
             TreeType treeType = SaplingBlock.treeType;
             SaplingBlock.treeType = null;
-            List<BlockState> blocks = new ArrayList<>(world.capturedBlockStates.values());
-            world.capturedBlockStates.clear();
+            List<BlockState> blocks = new ArrayList<>(worldData.capturedBlockStates.values()); // Folia - region threading
+            worldData.capturedBlockStates.clear(); // Folia - region threading
             StructureGrowEvent structureEvent = null;
 
             if (treeType != null) {
diff --git a/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java b/src/main/java/org/bukkit/craftbukkit/command/ConsoleCommandCompleter.java
index cd4ad8261e56365850068db1d83d6a8454026737..c098ae9f057a3dcc77c61555feb870452e947ae7 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.RegionisedServer.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.RegionisedServer.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 78f53ee557276de85f0431ebcb146445b1f4fb92..ab6db7c5193a7c4b3f9433c6997dd24c76a84904 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -200,6 +200,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
     private EntityDamageEvent lastDamageEvent;
     private final CraftPersistentDataContainer persistentDataContainer = new CraftPersistentDataContainer(CraftEntity.DATA_TYPE_REGISTRY);
     protected net.kyori.adventure.pointer.Pointers adventure$pointers; // Paper - implement pointers
+    public final io.papermc.paper.threadedregions.EntityScheduler taskScheduler = new io.papermc.paper.threadedregions.EntityScheduler(this); // Folia - region threading
 
     public CraftEntity(final CraftServer server, final Entity entity) {
         this.server = server;
@@ -556,6 +557,11 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
 
     @Override
     public boolean teleport(Location location, TeleportCause cause, boolean ignorePassengers, boolean dismount) {
+        // 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();
@@ -1206,7 +1212,7 @@ 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;
@@ -1270,30 +1276,38 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         Preconditions.checkArgument(location != null, "location");
         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());
-            }
-            net.minecraft.server.MinecraftServer.getServer().scheduleOnMain(() -> {
-                try {
-                    ret.complete(CraftEntity.this.teleport(locationClone, cause) ? Boolean.TRUE : Boolean.FALSE);
-                } catch (Throwable throwable) {
-                    if (throwable instanceof ThreadDeath) {
-                        throw (ThreadDeath)throwable;
+        boolean scheduled = this.taskScheduler.schedule(
+            // success
+            (Entity nmsEntity) -> {
+                boolean success = nmsEntity.teleportAsync(
+                    ((CraftWorld)locationClone.getWorld()).getHandle(),
+                    new net.minecraft.world.phys.Vec3(locationClone.getX(), locationClone.getY(), locationClone.getZ()),
+                    null, null, net.minecraft.world.phys.Vec3.ZERO,
+                    cause == null ? TeleportCause.UNKNOWN : cause,
+                    Entity.TELEPORT_FLAG_LOAD_CHUNK,
+                    (Entity entityTp) -> {
+                        ret.complete(Boolean.TRUE);
                     }
-                    net.minecraft.server.MinecraftServer.LOGGER.error("Failed to teleport entity " + CraftEntity.this, throwable);
-                    ret.completeExceptionally(throwable);
+                );
+                if (!success) {
+                    ret.complete(Boolean.FALSE);
                 }
-            });
-        });
+            },
+            // retired
+            (Entity nmsEntity) -> {
+                ret.complete(Boolean.FALSE);
+            },
+            1L
+        );
+
+        if (!scheduled) {
+            ret.complete(Boolean.FALSE);
+        }
 
         return ret;
+        // Folia end - region threading
     }
 
     @Override
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index 0351eb67bac6ce257f820af60aa3bba9f45da687..88006751825515966dcea1f779ac5452c8ddd964 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -1702,7 +1702,7 @@ 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());
         }
@@ -1765,7 +1765,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
             this.getHandle().connection.send(ClientboundPlayerInfoUpdatePacket.createPlayerInitializing(List.of(otherPlayer)));
         }
 
-        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 6a52ae70b5f7fd9953b6b2605cae722f606e7fec..2a6fe4a3fdba9d0027a2e445b694afc80a18053c 100644
--- a/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
+++ b/src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java
@@ -228,8 +228,8 @@ import org.bukkit.event.entity.SpawnerSpawnEvent; // Spigot
 public class CraftEventFactory {
     public static final DamageSource MELTING = CraftDamageSource.copyOf(DamageSource.ON_FIRE);
     public static final DamageSource POISON = CraftDamageSource.copyOf(DamageSource.MAGIC);
-    public static org.bukkit.block.Block blockDamage; // For use in EntityDamageByBlockEvent
-    public static Entity entityDamage; // For use in EntityDamageByEntityEvent
+    public static final ThreadLocal<org.bukkit.block.Block> blockDamageRT = new ThreadLocal<>(); // For use in EntityDamageByBlockEvent
+    public static final ThreadLocal<Entity> entityDamageRT = new ThreadLocal<>(); // For use in EntityDamageByEntityEvent
 
     // helper methods
     private static boolean canBuild(ServerLevel world, Player player, int x, int z) {
@@ -842,7 +842,7 @@ 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 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
         if (!(world instanceof Level)) {
@@ -853,7 +853,7 @@ 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()) {
@@ -968,8 +968,8 @@ public class CraftEventFactory {
     private static EntityDamageEvent handleEntityDamageEvent(Entity entity, DamageSource source, Map<DamageModifier, Double> modifiers, Map<DamageModifier, Function<? super Double, Double>> modifierFunctions, boolean cancelled) {
         if (source.isExplosion()) {
             DamageCause damageCause;
-            Entity damager = CraftEventFactory.entityDamage;
-            CraftEventFactory.entityDamage = null;
+            Entity damager = CraftEventFactory.entityDamageRT.get(); // Folia - region threading
+            CraftEventFactory.entityDamageRT.set(null); // Folia - region threading
             EntityDamageEvent event;
             if (damager == null) {
                 event = new EntityDamageByBlockEvent(null, entity.getBukkitEntity(), DamageCause.BLOCK_EXPLOSION, modifiers, modifierFunctions);
@@ -1022,13 +1022,13 @@ public class CraftEventFactory {
             }
             return event;
         } else if (source == DamageSource.LAVA) {
-            EntityDamageEvent event = (new EntityDamageByBlockEvent(CraftEventFactory.blockDamage, entity.getBukkitEntity(), DamageCause.LAVA, modifiers, modifierFunctions));
+            EntityDamageEvent event = (new EntityDamageByBlockEvent(CraftEventFactory.blockDamageRT.get(), entity.getBukkitEntity(), DamageCause.LAVA, modifiers, modifierFunctions)); // Folia - region threading
             event.setCancelled(cancelled);
 
-            Block damager = CraftEventFactory.blockDamage;
-            CraftEventFactory.blockDamage = null; // SPIGOT-6639: Clear blockDamage to allow other entity damage during event call
+            Block damager = CraftEventFactory.blockDamageRT.get();
+            CraftEventFactory.blockDamageRT.set(null); // SPIGOT-6639: Clear blockDamage to allow other entity damage during event call // Folia - region threading
             CraftEventFactory.callEvent(event);
-            CraftEventFactory.blockDamage = damager; // SPIGOT-6639: Re-set blockDamage so that other entities which are also getting damaged have the right cause
+            CraftEventFactory.blockDamageRT.set(damager); // SPIGOT-6639: Re-set blockDamage so that other entities which are also getting damaged have the right cause // Folia - region threading
 
             if (!event.isCancelled()) {
                 event.getEntity().setLastDamageCause(event);
@@ -1036,9 +1036,9 @@ public class CraftEventFactory {
                 entity.lastDamageCancelled = true; // SPIGOT-5339, SPIGOT-6252, SPIGOT-6777: Keep track if the event was canceled
             }
             return event;
-        } else if (CraftEventFactory.blockDamage != null) {
+        } else if (CraftEventFactory.blockDamageRT.get() != null) { // Folia - region threading
             DamageCause cause = null;
-            Block damager = CraftEventFactory.blockDamage;
+            Block damager = CraftEventFactory.blockDamageRT.get(); // Folia - region threading
             if (source == DamageSource.CACTUS || source == DamageSource.SWEET_BERRY_BUSH || source == DamageSource.STALAGMITE || "fallingStalactite".equals(source.msgId) || "anvil".equals(source.msgId)) {
                 cause = DamageCause.CONTACT;
             } else if (source == DamageSource.HOT_FLOOR) {
@@ -1053,9 +1053,9 @@ public class CraftEventFactory {
             EntityDamageEvent event = new EntityDamageByBlockEvent(damager, entity.getBukkitEntity(), cause, modifiers, modifierFunctions);
             event.setCancelled(cancelled);
 
-            CraftEventFactory.blockDamage = null; // SPIGOT-6639: Clear blockDamage to allow other entity damage during event call
+            CraftEventFactory.blockDamageRT.set(null); // SPIGOT-6639: Clear blockDamage to allow other entity damage during event call // Folia - region threading
             CraftEventFactory.callEvent(event);
-            CraftEventFactory.blockDamage = damager; // SPIGOT-6639: Re-set blockDamage so that other entities which are also getting damaged have the right cause
+            CraftEventFactory.blockDamageRT.set(damager); // SPIGOT-6639: Re-set blockDamage so that other entities which are also getting damaged have the right cause // Folia - region threading
 
             if (!event.isCancelled()) {
                 event.getEntity().setLastDamageCause(event);
@@ -1063,10 +1063,10 @@ public class CraftEventFactory {
                 entity.lastDamageCancelled = true; // SPIGOT-5339, SPIGOT-6252, SPIGOT-6777: Keep track if the event was canceled
             }
             return event;
-        } else if (CraftEventFactory.entityDamage != null) {
+        } else if (CraftEventFactory.entityDamageRT.get() != null) { // Folia - region threading
             DamageCause cause = null;
-            CraftEntity damager = CraftEventFactory.entityDamage.getBukkitEntity();
-            CraftEventFactory.entityDamage = null;
+            CraftEntity damager = CraftEventFactory.entityDamageRT.get().getBukkitEntity();
+            CraftEventFactory.entityDamageRT.set(null); // Folia - region threading
             if ("fallingStalactite".equals(source.msgId) || "fallingBlock".equals(source.msgId) || "anvil".equals(source.msgId)) {
                 cause = DamageCause.FALLING_BLOCK;
             } else if (damager instanceof LightningStrike) {
diff --git a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
index cdefb2025eedea7e204d70d568adaf1c1ec4c03c..9136fb30db749737e9f189d0901024fcad02e402 100644
--- a/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
+++ b/src/main/java/org/bukkit/craftbukkit/scheduler/CraftScheduler.java
@@ -533,6 +533,7 @@ 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/spigotmc/ActivationRange.java b/src/main/java/org/spigotmc/ActivationRange.java
index e881584d38dc354204479863f004e974a0ac6c07..7d99ba41a3178f5321403eb7749f0a4b898ad0a9 100644
--- a/src/main/java/org/spigotmc/ActivationRange.java
+++ b/src/main/java/org/spigotmc/ActivationRange.java
@@ -65,26 +65,27 @@ public class ActivationRange
 
     private static int checkInactiveWakeup(Entity entity) {
         Level world = entity.level;
+        io.papermc.paper.threadedregions.RegionisedWorldData worldData = world.getCurrentWorldData(); // Folia - threaded regions
         SpigotWorldConfig config = world.spigotConfig;
-        long inactiveFor = MinecraftServer.currentTick - entity.activatedTick;
+        long inactiveFor = io.papermc.paper.threadedregions.RegionisedServer.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;
             }
         }
@@ -174,10 +175,11 @@ 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.RegionisedWorldData 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
 
@@ -191,9 +193,9 @@ 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.RegionisedServer.getCurrentTick(); // Folia - region threading
             if ( world.spigotConfig.ignoreSpectatorActivation && player.isSpectator() )
             {
                 continue;
@@ -215,7 +217,7 @@ public class ActivationRange
             java.util.List<Entity> entities = world.getEntities((Entity)null, maxBB, (e) -> !(e instanceof net.minecraft.world.entity.Marker)); // Don't tick markers
             for (int i = 0; i < entities.size(); i++) {
                 Entity entity = entities.get(i);
-                ActivationRange.activateEntity(entity);
+                if (io.papermc.paper.util.TickThread.isTickThreadFor(entity)) ActivationRange.activateEntity(entity); // Folia - region ticking
             }
             // Paper end
         }
@@ -229,16 +231,16 @@ public class ActivationRange
      */
     private static void activateEntity(Entity entity)
     {
-        if ( MinecraftServer.currentTick > entity.activatedTick )
+        if ( io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick() > entity.activatedTick ) // Folia - threaded regions
         {
             if ( entity.defaultActivationState )
             {
-                entity.activatedTick = MinecraftServer.currentTick;
+                entity.activatedTick = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick(); // Folia - threaded regions
                 return;
             }
             if ( entity.activationType.boundingBox.intersects( entity.getBoundingBox() ) )
             {
-                entity.activatedTick = MinecraftServer.currentTick;
+                entity.activatedTick = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick(); // Folia - threaded regions
             }
         }
     }
@@ -261,10 +263,10 @@ public class ActivationRange
         if (entity.remainingFireTicks > 0) {
             return 2;
         }
-        if (entity.activatedImmunityTick >= MinecraftServer.currentTick) {
+        if (entity.activatedImmunityTick >= io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick()) { // Folia - threaded regions
             return 1;
         }
-        long inactiveFor = MinecraftServer.currentTick - entity.activatedTick;
+        long inactiveFor = io.papermc.paper.threadedregions.RegionisedServer.getCurrentTick() - entity.activatedTick; // Folia - threaded regions
         // Paper end
         // quick checks.
         if ( (entity.activationType != ActivationType.WATER && entity.wasTouchingWater && entity.isPushedByFluid()) ) // Paper
@@ -387,19 +389,19 @@ public class ActivationRange
         }
         // Paper end
 
-        boolean isActive = entity.activatedTick >= MinecraftServer.currentTick;
+        boolean isActive = entity.activatedTick >= io.papermc.paper.threadedregions.RegionisedServer.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.RegionisedServer.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.RegionisedServer.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 3112a8695639c402e9d18710acbc11cff5611e9c..72976bdb3db5d0066599272fab1055b2e20c5b26 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.RegionisedServer.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 612c3169c3463d702b85975e1db79ae6e47d60d0..6f77134ba451e7bd6bcba1000134ce8a2c762979 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( timeoutTime, 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 5503ad6a93d331771a0e92c0da6adedf2ac81aff..a06408a10cb24c203cfc25f25ccd37ac1a587a1a 100644
--- a/src/main/java/org/spigotmc/SpigotWorldConfig.java
+++ b/src/main/java/org/spigotmc/SpigotWorldConfig.java
@@ -425,7 +425,7 @@ 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 )