Adding a creature

Guide for adding a new creature to the game — from the entity definition to the spawn rules.

Files you'll touch

File	What it defines
`assets/common/entity/wild/`	RON template for the creature
`assets/common/abilities/`	Abilities it uses in combat
`world/src/layer/wildlife.rs`	Spawn rules by biome
`assets/world/wildlife/`	Spawn tables in RON

Step 1: Create the entity template

Creatures go in assets/common/entity/wild/ organized by type:

assets/common/entity/wild/aggressive/cave_troll.ron
assets/common/entity/wild/peaceful/deer.ron

Example — cave troll:

EntityConfig(
    name: Name("Trol de Cueva"),
    body: Body(
        kind: BipedLarge(BipedLargeBody(
            species: Troll,
            body_type: Male,
        )),
    ),
    alignment: Alignment::Enemy,
    loot: LootSpec::LootTable(
        "common.loot_tables.creatures.biped_large.troll",
    ),
    skillset_asset: Some("common.skillset.biped_large.troll"),
    flee_health: 0.1,
    idle_wander_factor: 0.5,
    aggro_range: 15.0,
)

Example — deer (peaceful creature):

EntityConfig(
    name: Name("Ciervo"),
    body: Body(
        kind: QuadrupedMedium(QuadrupedMediumBody(
            species: Deer,
            body_type: Male,
        )),
    ),
    alignment: Alignment::Wild,
    loot: LootSpec::LootTable(
        "common.loot_tables.creatures.quadruped_medium.deer",
    ),
    skillset_asset: None,
    flee_health: 0.5,
    idle_wander_factor: 1.0,
    aggro_range: 0.0,
)

Key fields

Field	Description
`alignment`	`Wild` (flees), `Enemy` (attacks), `Passive` (ignores)
`flee_health`	% health at which it starts fleeing (0.0 = never flees)
`aggro_range`	Radius at which it detects and attacks players
`idle_wander_factor`	How much it wanders when calm
`skillset_asset`	Combat abilities. `None` for creatures with no attack

Step 2: Create the loot table

Create the loot table in assets/common/loot_tables/creatures/:

// assets/common/loot_tables/creatures/biped_large/troll.ron
LootSpec::MultiDrop(
    drops: [
        (1.0, LootSpec::Item("common.items.crafting_ing.stone.granite")),
        (0.6, LootSpec::Item("common.items.crafting_ing.leather.tough_leather")),
        (0.2, LootSpec::Item("common.items.weapons.hammer.troll_hammer")),
    ],
)

Step 3: Define spawn rules

Add the creature to the wildlife table for the biome where it should appear. The tables are in assets/world/wildlife/:

// In the relevant biome table (e.g. mountains.ron)
SpawnEntry(
    name: "cave_troll",
    rules: [
        SpawnRule(
            // spawns near caves and in rocky areas
            min_time: NoDawn,
            max_time: NoDawn,
            threshold: 0.3,
            group_size: (1, 2),
            entity: EntityConfig(
                asset: "common.entity.wild.aggressive.cave_troll",
            ),
        ),
    ],
),

Alternatively, you can register the spawn in code in world/src/layer/wildlife.rs if you need more complex logic (spawn conditional on computed biome, variable density, etc.).

Step 4: Assign combat abilities

If the creature attacks, create or reuse a skillset in assets/common/skillset/:

// assets/common/skillset/biped_large/troll.ron
SkillSetConfig(
    guard_resist: 0.6,
    body_size_modifier: 1.5,
    primary: Some("common.abilities.biped_large.troll.basic_attack"),
    secondary: Some("common.abilities.biped_large.troll.shockwave"),
    abilities: [],
)

And the individual abilities in assets/common/abilities/biped_large/troll/:

// basic_attack.ron
BasicMelee(
    energy_cost: 0.0,
    buildup_duration: 0.6,
    swing_duration: 0.2,
    recover_duration: 0.5,
    melee_constructor: MeleeConstructor(
        kind: Bash,
        scaled: None,
        range: 4.0,
        angle: 45.0,
        damage: 28.0,
        knockback: 15.0,
        poise_damage: 50.0,
    ),
)

Step 5: Verify in-game

cargo build
cargo run --bin xindeler-server

To spawn the creature directly and test it without hunting for it in the world:

/summon common.entity.wild.aggressive.cave_troll

Verify:

Correct model and name
Combat behavior (aggro, fleeing)
Loot on death
That the server doesn't crash on death or when it leaves a player's range

Step 6: Commit

git add assets/common/entity/wild/aggressive/cave_troll.ron
git add assets/common/loot_tables/creatures/biped_large/troll.ron
git add assets/common/skillset/biped_large/troll.ron
git add assets/common/abilities/biped_large/troll/
git add assets/world/wildlife/mountains.ron  # if you modified it
git commit -m "feat: add cave troll creature with loot and spawn rules"

Files you'll touch​

Step 1: Create the entity template​

Key fields​

Step 2: Create the loot table​

Step 3: Define spawn rules​

Step 4: Assign combat abilities​

Step 5: Verify in-game​

Step 6: Commit​