diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000000..adb7fb8632
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+default: help
+
+.PHONY: help
+help:
+	@echo "  * gen-biomes version=<version> - Generate biomes for the given version"
+
+.PHONY: gen-biomes
+gen-biomes:
+	@echo "Generating biomes for $(version)"
+	@curl "https://raw.githubusercontent.com/MockBukkit/MockBukkit/refs/heads/v$(version)/src/main/resources/keyed/worldgen/biome.json" -s \
+		| jq '[ .values[].key]' \
+		> "src/test/resources/biomes/$(version).x.json"
diff --git a/pom.xml b/pom.xml
index 5bc0d0d651..be95bc63b9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -14,7 +14,7 @@
     <packaging>jar</packaging>
 
     <!-- Project Info -->
-    <description>Slimefun is a Spigot/Paper plugin that simulates a modpack-like atmosphere by adding over 500 new items and recipes to your Minecraft Server.</description>
+    <description>Slimefun is a Paper plugin that simulates a modpack-like atmosphere by adding over 500 new items and recipes to your Minecraft Server.</description>
     <url>https://github.com/Slimefun/Slimefun4</url>
 
     <properties>
@@ -29,8 +29,8 @@
         <maven.compiler.testTarget>21</maven.compiler.testTarget>
 
         <!-- Spigot properties -->
-        <spigot.version>1.20.6</spigot.version>
-        <spigot.javadocs>https://hub.spigotmc.org/javadocs/spigot/</spigot.javadocs>
+        <paper.version>1.21.1</paper.version>
+        <paper.javadocs>https://hub.spigotmc.org/javadocs/spigot/</paper.javadocs>
 
         <!-- Default settings for sonarcloud.io -->
         <sonar.projectKey>Slimefun_Slimefun4</sonar.projectKey>
@@ -238,7 +238,7 @@
                 <!-- Javadocs -->
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
-                <version>3.7.0</version>
+                <version>3.10.0</version>
 
                 <configuration>
                     <reportOutputDirectory>${project.basedir}</reportOutputDirectory>
@@ -251,7 +251,7 @@
 
                     <links>
                         <!-- We can reference the Spigot API in our Javadocs -->
-                        <link>${spigot.javadocs}</link>
+                        <link>${paper.javadocs}</link>
                     </links>
 
                     <!-- We can group packages together in our Javadocs -->
@@ -367,6 +367,14 @@
             <scope>compile</scope>
         </dependency>
 
+        <!-- Paper -->
+        <dependency>
+            <groupId>io.papermc.paper</groupId>
+            <artifactId>paper-api</artifactId>
+            <version>${paper.version}-R0.1-SNAPSHOT</version>
+            <scope>provided</scope>
+        </dependency>
+
         <!-- Testing dependencies -->
         <dependency>
             <groupId>org.junit.jupiter</groupId>
@@ -389,7 +397,7 @@
         <dependency>
             <groupId>com.github.MockBukkit</groupId>
             <artifactId>MockBukkit</artifactId>
-            <version>c7cc678834</version>
+            <version>v3.130.2</version>
             <scope>test</scope>
 
             <exclusions>
@@ -401,13 +409,6 @@
                 </exclusion>
             </exclusions>
         </dependency>
-        <!-- Override Spigot with Paper tests as a CommandMap ctor which MockBukkit uses only exists on Paper but not in Spigot -->
-        <dependency>
-            <groupId>io.papermc.paper</groupId>
-            <artifactId>paper-api</artifactId>
-            <version>1.20.6-R0.1-SNAPSHOT</version>
-            <scope>test</scope>
-        </dependency>
 
         <!-- Third party plugin integrations / soft dependencies -->
         <dependency>
@@ -515,12 +516,6 @@
             <version>2.6</version>
             <scope>compile</scope>
         </dependency>
-        <dependency>
-            <groupId>org.spigotmc</groupId>
-            <artifactId>spigot-api</artifactId>
-            <version>${spigot.version}-R0.1-SNAPSHOT</version>
-            <scope>provided</scope>
-        </dependency>
         <dependency>
             <groupId>com.mojang</groupId>
             <artifactId>authlib</artifactId>
diff --git a/src/main/java/io/github/thebusybiscuit/slimefun4/api/MinecraftVersion.java b/src/main/java/io/github/thebusybiscuit/slimefun4/api/MinecraftVersion.java
index 4fc0160ac6..afad06e3bc 100644
--- a/src/main/java/io/github/thebusybiscuit/slimefun4/api/MinecraftVersion.java
+++ b/src/main/java/io/github/thebusybiscuit/slimefun4/api/MinecraftVersion.java
@@ -55,6 +55,12 @@ public enum MinecraftVersion {
      */
     MINECRAFT_1_20_5(20, 5, "1.20.5+"),
 
+     /**
+     * This constant represents Minecraft (Java Edition) Version 1.21
+     * ("Tricky Trials")
+     */
+    MINECRAFT_1_21(21, 0, "1.21.x"),
+
     /**
      * This constant represents an exceptional state in which we were unable
      * to identify the Minecraft Version we are using
diff --git a/src/main/java/io/github/thebusybiscuit/slimefun4/api/items/SlimefunItemStack.java b/src/main/java/io/github/thebusybiscuit/slimefun4/api/items/SlimefunItemStack.java
index 611e85df6d..8ae4a86baa 100644
--- a/src/main/java/io/github/thebusybiscuit/slimefun4/api/items/SlimefunItemStack.java
+++ b/src/main/java/io/github/thebusybiscuit/slimefun4/api/items/SlimefunItemStack.java
@@ -307,7 +307,7 @@ public void lock() {
 
     @Override
     public ItemStack clone() {
-        return new SlimefunItemStack(id, this);
+        return new SlimefunItemStack(id, super.clone());
     }
 
     @Override
diff --git a/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/magical/runes/EnchantmentRune.java b/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/magical/runes/EnchantmentRune.java
index 33e54e7544..d7a2f03c08 100644
--- a/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/magical/runes/EnchantmentRune.java
+++ b/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/magical/runes/EnchantmentRune.java
@@ -50,7 +50,7 @@ public EnchantmentRune(ItemGroup itemGroup, SlimefunItemStack item, RecipeType r
         super(itemGroup, item, recipeType, recipe);
 
         for (Material mat : Material.values()) {
-            if (Slimefun.instance().isUnitTest() && mat.isLegacy()) continue;
+            if (mat.isLegacy() || !mat.isItem()) continue;
 
             List<Enchantment> enchantments = new ArrayList<>();
 
diff --git a/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/tools/ExplosiveTool.java b/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/tools/ExplosiveTool.java
index 6fe1174e4f..59fcd86d00 100644
--- a/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/tools/ExplosiveTool.java
+++ b/src/main/java/io/github/thebusybiscuit/slimefun4/implementation/items/tools/ExplosiveTool.java
@@ -1,7 +1,9 @@
 package io.github.thebusybiscuit.slimefun4.implementation.items.tools;
 
+import java.lang.reflect.Constructor;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.logging.Level;
 
 import javax.annotation.Nonnull;
 import javax.annotation.ParametersAreNonnullByDefault;
@@ -9,6 +11,7 @@
 import dev.lone.itemsadder.api.CustomBlock;
 import org.bukkit.Bukkit;
 import org.bukkit.Effect;
+import org.bukkit.ExplosionResult;
 import org.bukkit.Material;
 import org.bukkit.block.Block;
 import org.bukkit.entity.Player;
@@ -17,6 +20,7 @@
 import org.bukkit.inventory.ItemStack;
 
 import io.github.bakedlibs.dough.protection.Interaction;
+import io.github.thebusybiscuit.slimefun4.api.MinecraftVersion;
 import io.github.thebusybiscuit.slimefun4.api.events.ExplosiveToolBreakBlocksEvent;
 import io.github.thebusybiscuit.slimefun4.api.items.ItemGroup;
 import io.github.thebusybiscuit.slimefun4.api.items.ItemSetting;
@@ -48,6 +52,17 @@ public class ExplosiveTool extends SimpleSlimefunItem<ToolUseHandler> implements
     private final ItemSetting<Boolean> damageOnUse = new ItemSetting<>(this, "damage-on-use", true);
     private final ItemSetting<Boolean> callExplosionEvent = new ItemSetting<>(this, "call-explosion-event", false);
 
+    private static Constructor<?> pre21ExplodeEventConstructor;
+    static {
+        if (Slimefun.getMinecraftVersion().isBefore(MinecraftVersion.MINECRAFT_1_21)) {
+            try {
+                pre21ExplodeEventConstructor = BlockExplodeEvent.class.getConstructor(Block.class, List.class, float.class);
+            } catch (Exception e) {
+                Slimefun.logger().log(Level.SEVERE, "Could not find constructor for BlockExplodeEvent", e);
+            }
+        }
+    }
+
     @ParametersAreNonnullByDefault
     public ExplosiveTool(ItemGroup itemGroup, SlimefunItemStack item, RecipeType recipeType, ItemStack[] recipe) {
         super(itemGroup, item, recipeType, recipe);
@@ -78,7 +93,7 @@ private void breakBlocks(BlockBreakEvent e, Player p, ItemStack item, Block b, L
         List<Block> blocksToDestroy = new ArrayList<>();
 
         if (callExplosionEvent.getValue()) {
-            BlockExplodeEvent blockExplodeEvent = new BlockExplodeEvent(b, blocks, 0);
+            BlockExplodeEvent blockExplodeEvent = createNewBlockExplodeEvent(b, blocks, 0);
             Bukkit.getServer().getPluginManager().callEvent(blockExplodeEvent);
 
             if (!blockExplodeEvent.isCancelled()) {
@@ -186,4 +201,24 @@ private void breakBlock(BlockBreakEvent e, Player p, ItemStack item, Block b, Li
         damageItem(p, item);
     }
 
+    private BlockExplodeEvent createNewBlockExplodeEvent(
+        Block block,
+        List<Block> blocks,
+        float yield
+    ) {
+        var version = Slimefun.getMinecraftVersion();
+        if (version.isAtLeast(MinecraftVersion.MINECRAFT_1_21)) {
+            return new BlockExplodeEvent(block, block.getState(), blocks, yield, ExplosionResult.DESTROY);
+        } else if (pre21ExplodeEventConstructor != null) {
+            try {
+                return (BlockExplodeEvent) pre21ExplodeEventConstructor.newInstance(block, blocks, yield);
+            } catch (Exception e) {
+                Slimefun.logger().log(Level.SEVERE, "Could not find constructor for BlockExplodeEvent", e);
+            }
+
+            return null;
+        } else {
+            throw new IllegalStateException("BlockExplodeEvent constructor not found");
+        }
+    }
 }
diff --git a/src/test/java/io/github/thebusybiscuit/slimefun4/implementation/items/TestSlimefunItem.java b/src/test/java/io/github/thebusybiscuit/slimefun4/implementation/items/TestSlimefunItem.java
index 1bd21a0d3f..c2f07b5b99 100644
--- a/src/test/java/io/github/thebusybiscuit/slimefun4/implementation/items/TestSlimefunItem.java
+++ b/src/test/java/io/github/thebusybiscuit/slimefun4/implementation/items/TestSlimefunItem.java
@@ -9,8 +9,6 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.ValueSource;
 
 import io.github.bakedlibs.dough.items.CustomItemStack;
 import io.github.thebusybiscuit.slimefun4.api.exceptions.UnregisteredItemException;
@@ -110,7 +108,7 @@ void testRecipeType() {
     void testIsItem() {
         ItemStack item = new CustomItemStack(Material.BEACON, "&cItem Test");
         String id = "IS_ITEM_TEST";
-        SlimefunItem sfItem = TestUtilities.mockSlimefunItem(plugin, id, item);
+        SlimefunItem sfItem = TestUtilities.mockSlimefunItem(plugin, id, new CustomItemStack(Material.BEACON, "&cItem Test"));
         sfItem.register(plugin);
 
         Assertions.assertTrue(sfItem.isItem(sfItem.getItem()));
diff --git a/src/test/java/io/github/thebusybiscuit/slimefun4/utils/biomes/TestBiomeMapCompatibility.java b/src/test/java/io/github/thebusybiscuit/slimefun4/utils/biomes/TestBiomeMapCompatibility.java
index 99f7c6100f..d7ffca7d79 100644
--- a/src/test/java/io/github/thebusybiscuit/slimefun4/utils/biomes/TestBiomeMapCompatibility.java
+++ b/src/test/java/io/github/thebusybiscuit/slimefun4/utils/biomes/TestBiomeMapCompatibility.java
@@ -106,7 +106,8 @@ void testCompatibilities(String name, MinecraftVersion version) {
             MinecraftVersion.MINECRAFT_1_17,
             MinecraftVersion.MINECRAFT_1_18,
             MinecraftVersion.MINECRAFT_1_19,
-            MinecraftVersion.MINECRAFT_1_20
+            MinecraftVersion.MINECRAFT_1_20,
+            MinecraftVersion.MINECRAFT_1_21
         });
 
         testCases.put("oil_v1.16", new MinecraftVersion[] {
@@ -117,7 +118,8 @@ void testCompatibilities(String name, MinecraftVersion version) {
         testCases.put("oil_v1.18", new MinecraftVersion[] {
             MinecraftVersion.MINECRAFT_1_18,
             MinecraftVersion.MINECRAFT_1_19,
-            MinecraftVersion.MINECRAFT_1_20
+            MinecraftVersion.MINECRAFT_1_20,
+            MinecraftVersion.MINECRAFT_1_21
         });
 
         testCases.put("salt_v1.16", new MinecraftVersion[] {
@@ -128,7 +130,8 @@ void testCompatibilities(String name, MinecraftVersion version) {
         testCases.put("salt_v1.18", new MinecraftVersion[] {
             MinecraftVersion.MINECRAFT_1_18,
             MinecraftVersion.MINECRAFT_1_19,
-            MinecraftVersion.MINECRAFT_1_20
+            MinecraftVersion.MINECRAFT_1_20,
+            MinecraftVersion.MINECRAFT_1_21
         });
 
         testCases.put("uranium_v1.16", new MinecraftVersion[] {
@@ -142,7 +145,8 @@ void testCompatibilities(String name, MinecraftVersion version) {
         testCases.put("uranium_v1.18", new MinecraftVersion[] {
             MinecraftVersion.MINECRAFT_1_18,
             MinecraftVersion.MINECRAFT_1_19,
-            MinecraftVersion.MINECRAFT_1_20
+            MinecraftVersion.MINECRAFT_1_20,
+            MinecraftVersion.MINECRAFT_1_21
         });
         // @formatter:on
 
diff --git a/src/test/resources/biomes/1.20.5+.json b/src/test/resources/biomes/1.20.5+.json
index dfe92f1834..d6b3e4ece5 100644
--- a/src/test/resources/biomes/1.20.5+.json
+++ b/src/test/resources/biomes/1.20.5+.json
@@ -63,5 +63,5 @@
   "minecraft:jagged_peaks",
   "minecraft:stony_peaks",
   "minecraft:cherry_grove",
-  "minecraft:custom",
+  "minecraft:custom"
 ]
\ No newline at end of file
diff --git a/src/test/resources/biomes/1.20.x.json b/src/test/resources/biomes/1.20.x.json
index dfe92f1834..d6b3e4ece5 100644
--- a/src/test/resources/biomes/1.20.x.json
+++ b/src/test/resources/biomes/1.20.x.json
@@ -63,5 +63,5 @@
   "minecraft:jagged_peaks",
   "minecraft:stony_peaks",
   "minecraft:cherry_grove",
-  "minecraft:custom",
+  "minecraft:custom"
 ]
\ No newline at end of file
diff --git a/src/test/resources/biomes/1.21.x.json b/src/test/resources/biomes/1.21.x.json
new file mode 100644
index 0000000000..4a954bbbba
--- /dev/null
+++ b/src/test/resources/biomes/1.21.x.json
@@ -0,0 +1,67 @@
+[
+  "minecraft:badlands",
+  "minecraft:bamboo_jungle",
+  "minecraft:basalt_deltas",
+  "minecraft:beach",
+  "minecraft:birch_forest",
+  "minecraft:cherry_grove",
+  "minecraft:cold_ocean",
+  "minecraft:crimson_forest",
+  "minecraft:custom",
+  "minecraft:dark_forest",
+  "minecraft:deep_cold_ocean",
+  "minecraft:deep_dark",
+  "minecraft:deep_frozen_ocean",
+  "minecraft:deep_lukewarm_ocean",
+  "minecraft:deep_ocean",
+  "minecraft:desert",
+  "minecraft:dripstone_caves",
+  "minecraft:end_barrens",
+  "minecraft:end_highlands",
+  "minecraft:end_midlands",
+  "minecraft:eroded_badlands",
+  "minecraft:flower_forest",
+  "minecraft:forest",
+  "minecraft:frozen_ocean",
+  "minecraft:frozen_peaks",
+  "minecraft:frozen_river",
+  "minecraft:grove",
+  "minecraft:ice_spikes",
+  "minecraft:jagged_peaks",
+  "minecraft:jungle",
+  "minecraft:lukewarm_ocean",
+  "minecraft:lush_caves",
+  "minecraft:mangrove_swamp",
+  "minecraft:meadow",
+  "minecraft:mushroom_fields",
+  "minecraft:nether_wastes",
+  "minecraft:ocean",
+  "minecraft:old_growth_birch_forest",
+  "minecraft:old_growth_pine_taiga",
+  "minecraft:old_growth_spruce_taiga",
+  "minecraft:plains",
+  "minecraft:river",
+  "minecraft:savanna",
+  "minecraft:savanna_plateau",
+  "minecraft:small_end_islands",
+  "minecraft:snowy_beach",
+  "minecraft:snowy_plains",
+  "minecraft:snowy_slopes",
+  "minecraft:snowy_taiga",
+  "minecraft:soul_sand_valley",
+  "minecraft:sparse_jungle",
+  "minecraft:stony_peaks",
+  "minecraft:stony_shore",
+  "minecraft:sunflower_plains",
+  "minecraft:swamp",
+  "minecraft:taiga",
+  "minecraft:the_end",
+  "minecraft:the_void",
+  "minecraft:warm_ocean",
+  "minecraft:warped_forest",
+  "minecraft:windswept_forest",
+  "minecraft:windswept_gravelly_hills",
+  "minecraft:windswept_hills",
+  "minecraft:windswept_savanna",
+  "minecraft:wooded_badlands"
+]