Mob Origins

Mob origins are to mobs what player origins are to players: a JSON-defined bundle of powers attached to a LivingEntity, with weighted spawn rules and per-origin drops.

Authored at data/<ns>/origins/mob_origins/<id>.json; loaded by MobOriginDataManager after the player-origin / layer reload pipeline. NeoOrigins-native concept: no Origins-mod legacy format.

📖 See POWER_TYPES.md for the power list shared with player origins. The neoorigins:mob_behavior power (configurable aggression) is mob-only.

ℹ️ Status: this doc is a Phase-5 outline. Full field tables + examples land alongside Phase 6 and the v2.1.0 release.

File shape 

{
  "name": {"text": "Brutal Zombie"},
  "description": {"text": "A hostile zombie variant"},
  "icon": "minecraft:zombie_head",
  "target": {"entity_type": "minecraft:zombie"},
  "powers": ["neoorigins_custom:brutal_zombie_buffs"],
  "spawn_rules": { },
  "drops": { },
  "hidden": false
}

id is injected from the file path; do not write it in the JSON. (Same convention as player origins.)

Top-level fields

  • target: exactly one of entity_type (single id), entity_tag (tag id), or entity_types (array of ids). [TODO: examples + validation rules]
  • name is required; description and icon are optional.
  • powers: list of resolved power ids; unknown ids and powers that aren’t mob-applicable are skipped silently (no log line).
  • spawn_rules: optional. When absent the origin is never rolled at natural spawn (weight 0); it can still be attached with a spawn egg or /neoorigins mob apply. Fields:
    • weight (default 0): chance from 0 to 1 that the origin attaches when every other rule passes; 1 or more always attaches, 0 or less opts out.
    • spawn_reasons: lowercase vanilla spawn-reason names (EntitySpawnReason); empty or absent means any reason.
    • y_range, light_range: {"min": .., "max": ..} or a single int. Light is the block-light level at the spawn position.
    • time_of_day: any (default), day or night.
    • location: dimension, biome, biome_tag, biomes, structure, structure_tag. The other location fields (min_y, max_y, can_see_sky, allow_water_surface, allow_ocean_floor) are parsed but ignored here; use y_range for height.
    • mutex_group: recorded on the mob when the origin attaches, and a candidate is skipped if its group is already recorded. Because the roll stops at the first origin that attaches, this has no visible effect today.
    • replace (default false): parsed, but the spawn roll does not read it.

    Candidates whose target matches are tried in id order and the first one that passes attaches; a mob gets at most one origin.

  • drops: optional. Drop table layered onto vanilla loot by the neoorigins:mob_origin_drops global loot modifier. mode: additive (default) or replace (vanilla drops cleared). strategy: independent_chance (default: each entry rolls rolls times, default 1, at chance, default 1.0) or weighted_pool (pool_rolls picks, default 0, weighted by each entry’s weight, default 1). entries: [{item, count, chance, rolls, weight}], where item is required and count (default 1) takes the same int-or-range form as y_range. The modifier only runs when its carrier files are present in a loaded datapack; the Mob Origin Creator writes them into the world’s neoorigins_custom pack on save, and on server start they are written there if any loaded mob origin has drops (active after the next reload).
  • hidden (default false): parsed and stored, but nothing reads it yet.

The neoorigins:mob_behavior power

Configurable, piglin-style aggression. Three modes: NEUTRAL (no targeting), HOSTILE (always targets), CONDITIONAL (targets only while every hostile_when condition holds for the candidate player).

Config fields: aggression, hostile_when, retaliate, anger_linger_ticks, aggro_range, target_type, call_for_help. [TODO: full field table + examples; condition DSL reuses the existing entity-condition surface verbatim.]

Spawn-egg minting (Phase 4d)

Both surfaces target the saved origin id. Save the draft first if it’s new.

Other /neoorigins mob subcommands (permission level 2): apply <targets> <origin> attaches an origin to non-player living entities (without checking target), clear <targets> removes it, get <targets> reports it, and editor opens the Mob Origin Creator.

  • /neoorigins mob egg <origin> [entity_type] [count]: mints a vanilla <type>_spawn_egg ItemStack with the origin marker baked into ENTITY_DATA.
  • “Give Spawn Egg” button in the Mob Origin Creator’s Identity tab: same path, prompts for an entity type when the origin’s target is a tag or list.

Right-clicking the egg on the ground spawns the mob with the origin pre-attached. Right-clicking it on a Spawner reconfigures the spawner’s next-spawn data so its natural firings also carry the origin.

Live Mode (Phase 6: pending)

[TODO: looked-at apply / spawn here / active template. Section drafted when Phase 6 lands.]

Power compatibility

Not every power type works on mobs (HUD / keybind / food / starting-equipment / edible-item / orb-related types are player-only). Powers a mob origin lists are filtered through PowerType.appliesToMobs(config); ineligible powers are skipped without a log line and the rest are applied via MobOriginService.applyMobOriginPowers.

[TODO: full appliesToMobs() table, which power types fire on mobs and which are filtered out.]