Recipes: mobs and entities

A mob of your own

Status: Partly. It has its template's model, texture and behaviour. Unit tests check it; it hasn't been tried much in a running game yet.

You get: my_mod:ghoul, a zombie with 40 health that walks a little faster.

File: data/my_mod/horizon/entity_type/ghoul.json

{
  "template": "minecraft:zombie",
  "attributes": { "minecraft:max_health": 40.0, "minecraft:movement_speed": 0.3 }
}

File: assets/my_mod/lang/en_us.json

{ "entity.my_mod.ghoul": "Ghoul" }

• template is the vanilla mob it copies, such as minecraft:zombie or minecraft:villager.
• attributes change its defaults, by attribute id. Only attributes the template has: naming one it lacks stops the mod from loading.
• It saves and loads as itself, with what its template's class saves.
• It is in none of vanilla's entity tags (#minecraft:undead, ...). Add it yourself in data/minecraft/tags/entity_type/.

Try it: /summon my_mod:ghoul.

Its own sounds

Status: Works today.

Add sounds to the same file:

{
  "template": "minecraft:zombie",
  "sounds": {
    "ambient": "my_mod:entity.ghoul.ambient",
    "hurt": "minecraft:entity.husk.hurt",
    "death": "minecraft:entity.husk.death",
    "step": "none"
  }
}

• A slot you leave out keeps the template's sound. "none" mutes that slot.
• Your own sound ids come from assets/my_mod/sounds.json, in vanilla's resource pack format. See Sounds and particles.

What it drops

Status: Works today.

File: data/my_mod/loot_table/entities/ghoul.json

{
  "type": "minecraft:entity",
  "pools": [
    {
      "rolls": 1,
      "entries": [
        {
          "type": "minecraft:item",
          "name": "my_mod:ruby",
          "modifier": [
            { "type": "minecraft:set_count", "count": { "type": "minecraft:uniform", "min": 0, "max": 2 } }
          ]
        }
      ]
    }
  ],
  "random_sequence": "my_mod:entities/ghoul"
}

The path gives the table: a mob my_mod:ghoul drops from my_mod:entities/ghoul, as vanilla's getDefaultLootTable does.

Spawning naturally

Status: Works today.

You get: ghouls spawn in Overworld biomes, in groups of 1 to 3.

File: data/my_mod/neoforge/biome_modifier/ghoul_spawns.json

{
  "type": "neoforge:add_spawns",
  "biomes": "#minecraft:is_overworld",
  "spawners": { "type": "my_mod:ghoul", "weight": 20, "minCount": 1, "maxCount": 3 }
}

• This is NeoForge's biome modifier format, which Sunrise reads from mods.
• biomes is an id, a #tag or a list. spawners is one object or a list.
• The mob joins its template's spawn category: a zombie copy spawns as a monster, at night or in the dark.

Where exactly it may stand (on what block, in what light) is set in code, with Registrar::declare_spawn_placement:

fn register(&self, r: &mut dyn Registrar, _: &RegistrationContext) {
    r.declare_spawn_placement("ghoul", SpawnPlacementRule {
        placement: SpawnPlacementType::OnGround,
        heightmap: Heightmap::MotionBlockingNoLeaves,
        spawnable_on: None,         // or Some("my_mod:ghoul_ground"): a block tag, no #
        light: SpawnLight::Dark,    // Any, Dark (a monster's) or Bright (an animal's)
        biome_tag: None,            // or Some("my_mod:haunted"): a biome tag
    }).unwrap();
}

Without it, the mob keeps its template's rules. More hooks to allow, stop or change spawns: Controlling spawns.

Spawning one from code

Status: Works today.

LevelRef::spawn_mob spawns a mob as /summon would, and returns its handle:

// Inside any server hook, with `host: &mut dyn ServerHost`.
let dimension = host.dimension();
if let Some(level) = host.level(dimension) {
    let ghoul = level.spawn_mob(host, "my_mod:ghoul", [0.5, 70.0, 0.5], SpawnReason::Command);
    // None: nothing spawned (not a mob, unloaded chunk, a mod cancelled it...).
}

For a complete hook to put it in, see A command that spawns a mob.

Spawn rules and limits don't apply to spawn_mob, as they don't to /summon.

A throwable entity

A snowball-like projectile with its own item: A throwable item.

Its own AI

Status: Partly. Native mods only: entity Parts don't reach the sandbox (mod.wasm) yet.

An EntityPart adds goals to a mob type, yours or vanilla's, beside the template's own:

struct GhoulGoals;

#[mod_api::horizon_part]
impl EntityPart for GhoulGoals {
    fn register_goals(&self, goals: &mut GoalRegistrar<'_>) {
        // goals.add_goal(priority, YourGoal::default());
        // goals.add_target_goal(priority, YourTargetGoal::default());
    }
}

// In register:
r.entity_part("my_mod:ghoul", GhoulGoals);

You write each goal as a type that implements Goal. How goals run, what they may read and write, and brain behaviours: Entity parts and mob goals.

Its own model and texture

Status: Not yet. A mod mob draws as its template.

• What is missing: declaring an entity model and texture in data, as a resource pack would for a new mob.
• Workaround: a client hook can draw extra geometry for a mob each frame (mob_submit), and Model drawing shows how to draw a model. Keyframe animations: Entity keyframe animations.

What isn't here yet

• A mob class of your own (Java's extends Monster). Not yet. Workaround: copy the closest vanilla mob, then change it with attributes, sounds, goals and hooks such as entity_tick_post or living_damage_pre.
• A spawn egg. Not covered by these recipes. Workaround: /summon, a command of your own, or natural spawning.
• More gaps: API gaps: entities.