How to add a new mob in Minecraft

Minecraft is not just a game, it's a whole platform for creativity and learning programming! Today we will figure out how to create your own mob from scratch. This is a great way to get to know Java and understand the basics of game development.

What do we need?

Before you start, make sure you have:

• Java Development Kit (JDK) version 17 or higher

• IntelliJ IDEA (Community Edition is suitable)

• Minecraft Forge MDK (Mod Development Kit)

• Basic Java knowledge (variables, classes, methods)

Step 1: Setting up the environment

First, download Forge MDK from the official website files.minecraftforge.net. Unzip the archive into a separate folder and open the project in IntelliJ IDEA.

Run the command in the IDE terminal:

./gradlew genIntellijRuns

💡 Tip: This will set up the project for development. Wait for Gradle to download all dependencies — this may take a few minutes.

Step 2: Create a mob class

Let's create a simple mob — a friendly firefly that will fly and glow at night.

In the src/main/java/com/yourname/yourmod/entity folder, create the FireflyEntity.java file:

package com.yourname.yourmod.entity;

import net.minecraft.world.entity.EntityType;
import net.minecraft.world.entity.PathfinderMob;
import net.minecraft.world.entity.ai.attributes.AttributeSupplier;
import net.minecraft.world.entity.ai.attributes.Attributes;
import net.minecraft.world.entity.ai.goal.FloatGoal;
import net.minecraft.world.entity.ai.goal.WaterAvoidingRandomStrollGoal;
import net.minecraft.world.level.Level;

public class FireflyEntity extends PathfinderMob {
    
    public FireflyEntity(EntityType<? extends PathfinderMob> type, Level world) {
        super(type, world);
    }
    
    // Registering mob behavior
    @Override
    protected void registerGoals() {
        this.goalSelector.addGoal(0, new FloatGoal(this));
        this.goalSelector.addGoal(1, new WaterAvoidingRandomStrollGoal(this, 1.0D));
    }
    
    // Configure attributes (health, speed)
    public static AttributeSupplier.Builder createAttributes() {
        return PathfinderMob.createMobAttributes()
            .add(Attributes.MAX_HEALTH, 5.0D)
            .add(Attributes.MOVEMENT_SPEED, 0.25D);
    }
}

What's going on here?

• PathfinderMob — base class for mobs that can walk

• registerGoals() — a method where we determine the behavior of the mob (swimming, walking, attacking)

• createAttributes() — here we set the characteristics: health, speed, damage

Step 3: Register the mob

Now we need to "tell" the game about our mob. Create a class ModEntities.java:

package com.yourname.yourmod.entity;

import net.minecraft.world.entity.EntityType;
import net.minecraft.world.entity.MobCategory;
import net.minecraftforge.registries.DeferredRegister;
import net.minecraftforge.registries.ForgeRegistries;
import net.minecraftforge.registries.RegistryObject;

public class ModEntities {
    public static final DeferredRegister<EntityType<?>> ENTITIES = 
        DeferredRegister.create(ForgeRegistries.ENTITY_TYPES, "yourmod");
    
    public static final RegistryObject<EntityType<FireflyEntity>> FIREFLY = 
        ENTITIES.register("firefly", () -> EntityType.Builder
            .of(FireflyEntity::new, MobCategory.CREATURE)
            .sized(0.4F, 0.3F) // hitbox size
            .build("firefly"));
}

Don't forget to register ENTITIES in the main class of your mod:

@Mod("yourmod")
public class YourMod {
    public YourMod() {
        IEventBus bus = FMLJavaModLoadingContext.get().getModEventBus();
        ModEntities.ENTITIES.register(bus);
    }
}

Step 4: Create a model and texture

There is a mob, but it is invisible! You need to create a 3D model. You can use the program Blockbench - free editor for Minecraft models.

1. Create a simple model (cube for the body, small cubes for the wings)

2. Export as Java file

3. Place the model in src/main/java/com/yourname/yourmod/client/model/

4. Create a texture (16x16 pixels) and save it in src/main/resources/assets/yourmod/textures/entity/

Step 5: Mob Renderer

Create a class FireflyRenderer.java:

package com.yourname.yourmod.client.renderer;

import com.yourname.yourmod.entity.FireflyEntity;
import net.minecraft.client.renderer.entity.EntityRendererProvider;
import net.minecraft.client.renderer.entity.MobRenderer;
import net.minecraft.resources.ResourceLocation;

public class FireflyRenderer extends MobRenderer<FireflyEntity, FireflyModel> {
    
    private static final ResourceLocation TEXTURE = 
        new ResourceLocation("yourmod", "textures/entity/firefly.png");
    
    public FireflyRenderer(EntityRendererProvider.Context context) {
        super(context, new FireflyModel(context.bakeLayer(FireflyModel.LAYER)), 0.3F);
    }
    
    @Override
    public ResourceLocation getTextureLocation(FireflyEntity entity) {
        return TEXTURE;
    }
}

Step 6: Spawn the mob in the world

Let's add a mob to the natural spawn of the game. In the main mod class, add an event handler:

@SubscribeEvent
public static void onBiomeLoading(BiomeLoadingEvent event) {
    if (event.getCategory() == Biome.BiomeCategory.FOREST) {
        event.getSpawns().getSpawner(MobCategory.CREATURE)
            .add(new MobSpawnSettings.SpawnerData(
                ModEntities.FIREFLY.get(), 15, 2, 4));
    }
}

✅ Excellent! Now fireflies will appear in forest biomes!

Step 7: Testing

Run the game through IntelliJ IDEA (use the runClient configuration). Create a new world and check:

• Does the mob appear in the forest?

• Is the model displayed correctly?

• Does the behavior (walking, swimming) work?

💡 Tip: If something doesn't work, check the logs in the console. Forge describes all errors in detail.

Additional features

You can add a mob:

• Own sounds (steps, attack, death)

• Animations (wings fluttering, glowing)

• Unique behavior (attack, escape, search for food)

• Item drop in case of death

• Spawn through the summoning egg

@Override
protected void dropCustomDeathLoot(DamageSource source, int looting, boolean recentlyHit) {
    super.dropCustomDeathLoot(source, looting, recentlyHit);
    this.spawnAtLocation(Items.GLOWSTONE_DUST, 1);
}

Common mistakes of beginners

1. Forgot to register the mob — check that ENTITIES.register(bus) is called

2. Incorrect texture path — make sure that the paths in the code and the file system match

3. Did not generate a working environment — perform gradlew genIntellijRuns again

4. Outdated version of Forge - use the latest stable version for your Minecraft version

Do you want to explore this topic in more depth and create a really cool mob with unique mechanics?

In Codice we analyze in detail many other programming topics - from the basics of Java to the creation of complex projects. Each topic is accompanied by practical tasks that will help to consolidate the material.

Here you will learn:

• Work with Java on real examples

• Create mods, plugins, and games

• Understand code architecture and write clean code

• Solve problems like a real developer

And if you have any questions or need support, welcome to our active Telegram channel, where a large team of like-minded people has already gathered! We will always help you to deal with the problem, suggest the best solution and support you on the way of learning.

Join Kodik — programming can be clear and exciting! 🚀