diff --git a/src/main/java/fr/themode/demo/commands/SimpleCommand.java b/src/main/java/fr/themode/demo/commands/SimpleCommand.java
index 127f92e8a..9e0127f94 100644
--- a/src/main/java/fr/themode/demo/commands/SimpleCommand.java
+++ b/src/main/java/fr/themode/demo/commands/SimpleCommand.java
@@ -1,11 +1,9 @@
 package fr.themode.demo.commands;
 
-import fr.themode.demo.generator.ChunkGeneratorDemo;
-import net.minestom.server.MinecraftServer;
 import net.minestom.server.command.CommandProcessor;
+import net.minestom.server.entity.EntityCreature;
 import net.minestom.server.entity.Player;
 import net.minestom.server.instance.Instance;
-import net.minestom.server.world.Dimension;
 
 public class SimpleCommand implements CommandProcessor {
     @Override
@@ -24,15 +22,10 @@ public class SimpleCommand implements CommandProcessor {
 
         Instance instance = player.getInstance();
 
-        /*for (EntityCreature creature : instance.getCreatures()) {
+        for (EntityCreature creature : instance.getCreatures()) {
             creature.setPathTo(player.getPosition());
-        }*/
+        }
 
-        Instance inst = MinecraftServer.getInstanceManager().createInstanceContainer(Dimension.NETHER);
-        inst.enableAutoChunkLoad(true);
-        inst.setChunkGenerator(new ChunkGeneratorDemo());
-
-        player.setInstance(inst);
 
         return true;
     }
diff --git a/src/main/java/net/minestom/server/data/Data.java b/src/main/java/net/minestom/server/data/Data.java
index db06a817f..330647a6c 100644
--- a/src/main/java/net/minestom/server/data/Data.java
+++ b/src/main/java/net/minestom/server/data/Data.java
@@ -11,9 +11,13 @@ public class Data {
     protected ConcurrentHashMap<String, Object> data = new ConcurrentHashMap();
 
     public <T> void set(String key, T value, Class<T> type) {
-        if (DATA_MANAGER.getDataType(type) == null) {
-            throw new UnsupportedOperationException("Type " + type.getName() + " hasn't been registered in DataManager#registerType");
+        // Type registering is only relevant if data should be serialized
+        if (this instanceof SerializableData) {
+            if (DATA_MANAGER.getDataType(type) == null) {
+                throw new UnsupportedOperationException("Type " + type.getName() + " hasn't been registered in DataManager#registerType");
+            }
         }
+
         this.data.put(key, value);
     }
 
diff --git a/src/main/java/net/minestom/server/data/DataManager.java b/src/main/java/net/minestom/server/data/DataManager.java
index 65f52393e..fb536504e 100644
--- a/src/main/java/net/minestom/server/data/DataManager.java
+++ b/src/main/java/net/minestom/server/data/DataManager.java
@@ -2,6 +2,7 @@ package net.minestom.server.data;
 
 import net.minestom.server.data.type.CharacterData;
 import net.minestom.server.data.type.*;
+import net.minestom.server.data.type.array.ItemStackArrayData;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.utils.PrimitiveConversion;
 
@@ -27,6 +28,7 @@ public class DataManager {
         registerType(SerializableData.class, new SerializableDataData());
 
         registerType(ItemStack.class, new ItemStackData());
+        registerType(ItemStack[].class, new ItemStackArrayData());
     }
 
     public <T> void registerType(Class<T> clazz, DataType<T> dataType) {
diff --git a/src/main/java/net/minestom/server/data/DataType.java b/src/main/java/net/minestom/server/data/DataType.java
index 173776ddd..7051f1a02 100644
--- a/src/main/java/net/minestom/server/data/DataType.java
+++ b/src/main/java/net/minestom/server/data/DataType.java
@@ -1,9 +1,12 @@
 package net.minestom.server.data;
 
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
+
 public abstract class DataType<T> {
 
-    public abstract byte[] encode(T value);
+    public abstract void encode(PacketWriter packetWriter, T value);
 
-    public abstract T decode(byte[] value);
+    public abstract T decode(PacketReader packetReader, byte[] value);
 
 }
\ No newline at end of file
diff --git a/src/main/java/net/minestom/server/data/SerializableData.java b/src/main/java/net/minestom/server/data/SerializableData.java
index 93ec4cb26..66c84db24 100644
--- a/src/main/java/net/minestom/server/data/SerializableData.java
+++ b/src/main/java/net/minestom/server/data/SerializableData.java
@@ -1,5 +1,6 @@
 package net.minestom.server.data;
 
+import net.minestom.server.network.packet.PacketWriter;
 import net.minestom.server.utils.PrimitiveConversion;
 
 import java.io.ByteArrayOutputStream;
@@ -43,7 +44,9 @@ public class SerializableData extends Data {
             dos.writeShort(encodedName.length);
             dos.write(encodedName);
 
-            byte[] encodedValue = dataType.encode(value); // Data
+            PacketWriter packetWriter = new PacketWriter();
+            dataType.encode(packetWriter, value); // Encode
+            byte[] encodedValue = packetWriter.toByteArray(); // Retrieve bytes
             dos.writeInt(encodedValue.length);
             dos.write(encodedValue);
         }
diff --git a/src/main/java/net/minestom/server/data/type/BooleanData.java b/src/main/java/net/minestom/server/data/type/BooleanData.java
index 8826fa9be..e28bd41ef 100644
--- a/src/main/java/net/minestom/server/data/type/BooleanData.java
+++ b/src/main/java/net/minestom/server/data/type/BooleanData.java
@@ -1,15 +1,17 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class BooleanData extends DataType<Boolean> {
     @Override
-    public byte[] encode(Boolean value) {
-        return new byte[]{(byte) (value.booleanValue() ? 1 : 0)};
+    public void encode(PacketWriter packetWriter, Boolean value) {
+        packetWriter.writeBoolean(value);
     }
 
     @Override
-    public Boolean decode(byte[] value) {
-        return value[0] == 1;
+    public Boolean decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readBoolean();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/ByteData.java b/src/main/java/net/minestom/server/data/type/ByteData.java
index 61572927f..f50ddfb19 100644
--- a/src/main/java/net/minestom/server/data/type/ByteData.java
+++ b/src/main/java/net/minestom/server/data/type/ByteData.java
@@ -1,15 +1,17 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class ByteData extends DataType<Byte> {
     @Override
-    public byte[] encode(Byte value) {
-        return new byte[]{value};
+    public void encode(PacketWriter packetWriter, Byte value) {
+        packetWriter.writeByte(value);
     }
 
     @Override
-    public Byte decode(byte[] value) {
-        return value[0];
+    public Byte decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readByte();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/CharacterData.java b/src/main/java/net/minestom/server/data/type/CharacterData.java
index 050d3c080..68a75bd53 100644
--- a/src/main/java/net/minestom/server/data/type/CharacterData.java
+++ b/src/main/java/net/minestom/server/data/type/CharacterData.java
@@ -1,23 +1,18 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
-
-import java.nio.ByteBuffer;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class CharacterData extends DataType<Character> {
 
     @Override
-    public byte[] encode(Character value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Character.BYTES);
-        buffer.putChar(value);
-        return buffer.array();
+    public void encode(PacketWriter packetWriter, Character value) {
+        packetWriter.writeChar(value);
     }
 
     @Override
-    public Character decode(byte[] value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Character.BYTES);
-        buffer.put(value);
-        buffer.flip();
-        return buffer.getChar();
+    public Character decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readChar();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/DoubleData.java b/src/main/java/net/minestom/server/data/type/DoubleData.java
index 6fc47e291..72906de9b 100644
--- a/src/main/java/net/minestom/server/data/type/DoubleData.java
+++ b/src/main/java/net/minestom/server/data/type/DoubleData.java
@@ -1,23 +1,18 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
-
-import java.nio.ByteBuffer;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class DoubleData extends DataType<Double> {
 
     @Override
-    public byte[] encode(Double value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Double.BYTES);
-        buffer.putDouble(value);
-        return buffer.array();
+    public void encode(PacketWriter packetWriter, Double value) {
+        packetWriter.writeDouble(value);
     }
 
     @Override
-    public Double decode(byte[] value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Double.BYTES);
-        buffer.put(value);
-        buffer.flip();
-        return buffer.getDouble();
+    public Double decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readDouble();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/FloatData.java b/src/main/java/net/minestom/server/data/type/FloatData.java
index a4d370e5b..9e961d246 100644
--- a/src/main/java/net/minestom/server/data/type/FloatData.java
+++ b/src/main/java/net/minestom/server/data/type/FloatData.java
@@ -1,23 +1,18 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
-
-import java.nio.ByteBuffer;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class FloatData extends DataType<Float> {
 
     @Override
-    public byte[] encode(Float value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Float.BYTES);
-        buffer.putFloat(value);
-        return buffer.array();
+    public void encode(PacketWriter packetWriter, Float value) {
+        packetWriter.writeFloat(value);
     }
 
     @Override
-    public Float decode(byte[] value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Float.BYTES);
-        buffer.put(value);
-        buffer.flip();
-        return buffer.getFloat();
+    public Float decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readFloat();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/IntegerData.java b/src/main/java/net/minestom/server/data/type/IntegerData.java
index 01e1d859d..a55099728 100644
--- a/src/main/java/net/minestom/server/data/type/IntegerData.java
+++ b/src/main/java/net/minestom/server/data/type/IntegerData.java
@@ -1,23 +1,18 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
-
-import java.nio.ByteBuffer;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class IntegerData extends DataType<Integer> {
 
     @Override
-    public byte[] encode(Integer value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Integer.BYTES);
-        buffer.putInt(value);
-        return buffer.array();
+    public void encode(PacketWriter packetWriter, Integer value) {
+        packetWriter.writeVarInt(value);
     }
 
     @Override
-    public Integer decode(byte[] value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Integer.BYTES);
-        buffer.put(value);
-        buffer.flip();
-        return buffer.getInt();
+    public Integer decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readVarInt();
     }
 }
\ No newline at end of file
diff --git a/src/main/java/net/minestom/server/data/type/ItemStackData.java b/src/main/java/net/minestom/server/data/type/ItemStackData.java
index 1d38ad4c1..2b0a628ef 100644
--- a/src/main/java/net/minestom/server/data/type/ItemStackData.java
+++ b/src/main/java/net/minestom/server/data/type/ItemStackData.java
@@ -1,25 +1,18 @@
 package net.minestom.server.data.type;
 
-import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 import net.minestom.server.data.DataType;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.network.packet.PacketReader;
 import net.minestom.server.network.packet.PacketWriter;
-import net.minestom.server.utils.Utils;
 
 public class ItemStackData extends DataType<ItemStack> {
     @Override
-    public byte[] encode(ItemStack value) {
-        PacketWriter packetWriter = new PacketWriter();
+    public void encode(PacketWriter packetWriter, ItemStack value) {
         packetWriter.writeItemStack(value);
-        return packetWriter.toByteArray();
     }
 
     @Override
-    public ItemStack decode(byte[] value) {
-        ByteBuf buffer = Unpooled.wrappedBuffer(value);
-        ItemStack itemStack = Utils.readItemStack(new PacketReader(buffer));
-        return itemStack;
+    public ItemStack decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readSlot();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/LongData.java b/src/main/java/net/minestom/server/data/type/LongData.java
index 589f6b713..74cf6806e 100644
--- a/src/main/java/net/minestom/server/data/type/LongData.java
+++ b/src/main/java/net/minestom/server/data/type/LongData.java
@@ -1,22 +1,17 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
-
-import java.nio.ByteBuffer;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class LongData extends DataType<Long> {
     @Override
-    public byte[] encode(Long value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
-        buffer.putLong(value);
-        return buffer.array();
+    public void encode(PacketWriter packetWriter, Long value) {
+        packetWriter.writeLong(value);
     }
 
     @Override
-    public Long decode(byte[] value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
-        buffer.put(value);
-        buffer.flip();
-        return buffer.getLong();
+    public Long decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readLong();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/SerializableDataData.java b/src/main/java/net/minestom/server/data/type/SerializableDataData.java
index a86151645..44ad1f8fe 100644
--- a/src/main/java/net/minestom/server/data/type/SerializableDataData.java
+++ b/src/main/java/net/minestom/server/data/type/SerializableDataData.java
@@ -3,6 +3,8 @@ package net.minestom.server.data.type;
 import net.minestom.server.data.DataType;
 import net.minestom.server.data.SerializableData;
 import net.minestom.server.io.DataReader;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 import java.io.IOException;
 
@@ -10,9 +12,9 @@ import java.io.IOException;
 public class SerializableDataData extends DataType<SerializableData> {
 
     @Override
-    public byte[] encode(SerializableData value) {
+    public void encode(PacketWriter packetWriter, SerializableData value) {
         try {
-            return value.getSerializedData();
+            packetWriter.writeBytes(value.getSerializedData());
         } catch (IOException e) {
             e.printStackTrace();
             throw new IllegalArgumentException("error while writing the data");
@@ -20,7 +22,7 @@ public class SerializableDataData extends DataType<SerializableData> {
     }
 
     @Override
-    public SerializableData decode(byte[] value) {
+    public SerializableData decode(PacketReader packetReader, byte[] value) {
         return DataReader.readData(value, false);
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/ShortData.java b/src/main/java/net/minestom/server/data/type/ShortData.java
index 6296ceddf..a99a2f9b5 100644
--- a/src/main/java/net/minestom/server/data/type/ShortData.java
+++ b/src/main/java/net/minestom/server/data/type/ShortData.java
@@ -1,23 +1,18 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
-
-import java.nio.ByteBuffer;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class ShortData extends DataType<Short> {
 
     @Override
-    public byte[] encode(Short value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Short.BYTES);
-        buffer.putShort(value);
-        return buffer.array();
+    public void encode(PacketWriter packetWriter, Short value) {
+        packetWriter.writeShort(value);
     }
 
     @Override
-    public Short decode(byte[] value) {
-        ByteBuffer buffer = ByteBuffer.allocate(Short.BYTES);
-        buffer.put(value);
-        buffer.flip();
-        return buffer.getShort();
+    public Short decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readShort();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/StringData.java b/src/main/java/net/minestom/server/data/type/StringData.java
index 18e345193..405ed7f51 100644
--- a/src/main/java/net/minestom/server/data/type/StringData.java
+++ b/src/main/java/net/minestom/server/data/type/StringData.java
@@ -1,16 +1,18 @@
 package net.minestom.server.data.type;
 
 import net.minestom.server.data.DataType;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
 
 public class StringData extends DataType<String> {
 
     @Override
-    public byte[] encode(String value) {
-        return value.getBytes();
+    public void encode(PacketWriter packetWriter, String value) {
+        packetWriter.writeSizedString(value);
     }
 
     @Override
-    public String decode(byte[] value) {
-        return new String(value);
+    public String decode(PacketReader packetReader, byte[] value) {
+        return packetReader.readSizedString();
     }
 }
diff --git a/src/main/java/net/minestom/server/data/type/array/ItemStackArrayData.java b/src/main/java/net/minestom/server/data/type/array/ItemStackArrayData.java
new file mode 100644
index 000000000..9d4b61e34
--- /dev/null
+++ b/src/main/java/net/minestom/server/data/type/array/ItemStackArrayData.java
@@ -0,0 +1,30 @@
+package net.minestom.server.data.type.array;
+
+import net.minestom.server.data.DataType;
+import net.minestom.server.item.ItemStack;
+import net.minestom.server.network.packet.PacketReader;
+import net.minestom.server.network.packet.PacketWriter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ItemStackArrayData extends DataType<ItemStack[]> {
+    @Override
+    public void encode(PacketWriter packetWriter, ItemStack[] value) {
+        packetWriter.writeVarInt(value.length);
+        for (ItemStack itemStack : value) {
+            packetWriter.writeItemStack(itemStack);
+        }
+    }
+
+    @Override
+    public ItemStack[] decode(PacketReader packetReader, byte[] value) {
+        List<ItemStack> items = new ArrayList<>();
+        int size = packetReader.readVarInt();
+        for (int i = 0; i < size; i++) {
+            items.add(packetReader.readSlot());
+        }
+        ItemStack[] array = items.toArray(new ItemStack[items.size()]);
+        return array;
+    }
+}
diff --git a/src/main/java/net/minestom/server/io/DataReader.java b/src/main/java/net/minestom/server/io/DataReader.java
index c0ff92e4f..c5eb6516e 100644
--- a/src/main/java/net/minestom/server/io/DataReader.java
+++ b/src/main/java/net/minestom/server/io/DataReader.java
@@ -1,8 +1,11 @@
 package net.minestom.server.io;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.data.DataManager;
 import net.minestom.server.data.SerializableData;
+import net.minestom.server.network.packet.PacketReader;
 import net.minestom.server.utils.CompressionUtils;
 
 import java.io.ByteArrayInputStream;
@@ -45,7 +48,9 @@ public class DataReader {
                 Class type = Class.forName(new String(typeCache));
 
                 String name = new String(nameCache);
-                Object value = DATA_MANAGER.getDataType(type).decode(valueCache);
+                ByteBuf buffer = Unpooled.wrappedBuffer(valueCache);
+                PacketReader packetReader = new PacketReader(buffer);
+                Object value = DATA_MANAGER.getDataType(type).decode(packetReader, valueCache);
 
                 data.set(name, value, type);
             }
diff --git a/src/main/java/net/minestom/server/network/packet/PacketReader.java b/src/main/java/net/minestom/server/network/packet/PacketReader.java
index 76273117e..2c67fe377 100644
--- a/src/main/java/net/minestom/server/network/packet/PacketReader.java
+++ b/src/main/java/net/minestom/server/network/packet/PacketReader.java
@@ -30,6 +30,10 @@ public class PacketReader {
         return buffer.readShort();
     }
 
+    public char readChar() {
+        return buffer.readChar();
+    }
+
     public int readUnsignedShort() {
         return buffer.readUnsignedShort();
     }
diff --git a/src/main/java/net/minestom/server/network/packet/PacketWriter.java b/src/main/java/net/minestom/server/network/packet/PacketWriter.java
index e8204a686..6b2ffeeb6 100644
--- a/src/main/java/net/minestom/server/network/packet/PacketWriter.java
+++ b/src/main/java/net/minestom/server/network/packet/PacketWriter.java
@@ -38,6 +38,14 @@ public class PacketWriter {
         }
     }
 
+    public void writeChar(char s) {
+        try {
+            data.writeChar(s);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
     public void writeShort(short s) {
         try {
             data.writeShort(s);