Spawn Rules

Spawn rule files live in plugins/EmakiMobs/spawn_rules/*.yml. Each file can contain multiple rules under a rules: list.

File structure

rules:
  - mob_id: <mob id>
    type: <spawn type>
    # type-specific fields…

The loader accepts only two type values

The "Six spawn types" section below is outdated

The current loader only recognises type: natural and type: autonomous. Writing structure, biome, player_relative, day_interval or custom does not raise an error — it is logged as Unknown spawn type and the whole rule is skipped silently.

In the six-type sections below, everything except natural describes the old schema. The field descriptions are still useful as a reference, but the type values themselves no longer work. See autonomous — self-scheduled spawning for the current equivalents. The bundled spawn_rules/overworld.yml annotates each old type with its migration path.

Old type	Current equivalent	Migration notes
structure	autonomous + trigger: interval	interval_ticks moves up to the rule root; active_spawn and require_player_nearby are not current fields.
biome	autonomous + trigger: interval	biomes, interval_ticks and distance carry over; conditions.light_max / conditions.require_surface become root-level light_level_max / require_surface.
player_relative	autonomous + trigger: player_follow	distance, max_global, interval_ticks and count carry over; require_sky_access is not a current field.
day_interval	autonomous + trigger: day_interval	interval_days, on_day_start, max_global and count carry over; distance_from_player becomes distance.
custom	autonomous + trigger: interval	interval_ticks, distance, biomes, max_nearby and count carry over.

autonomous — self-scheduled spawning

Runs entirely outside vanilla spawn events, driven by its own scheduler. trigger selects the scheduling mode. If trigger is missing or unknown, the whole rule is skipped.

- mob_id: elite_zombie
  type: autonomous
  trigger: interval
  interval_ticks: 1200
  worlds:
    - world
  biomes:
    - plains
  distance:
    min: 16
    max: 64
  max_nearby: 4
  max_global: 10
  count:
    min: 1
    max: 2

The four triggers

trigger	Scheduling	Key fields
interval	Fixed tick interval, scans every online player	interval_ticks
player_follow	Fixed tick interval, picks one random online player each time	interval_ticks
day_interval	Counts in-game days	interval_days, on_day_start
cron	Fires on real system time via a Cron expression	cron

trigger values are case-insensitive. cron uses the 6-field Quartz format (second minute hour day-of-month month day-of-week); a blank or unparsable expression is logged as a warning and the rule never fires.

Fields

Field	Type	Default	Description
trigger	string	none (required)	Scheduling mode, see the table above.
interval_ticks	long	600	Spawn interval for interval / player_follow (ticks).
interval_days	int	1	In-game day interval for day_interval.
on_day_start	boolean	false	true = fire at sunrise; false = fire as soon as the counter is reached.
cron	string	""	Cron expression for trigger: cron.
worlds	string list	[] (any)	Restrict to these world names.
biomes	string list	[] (any)	Restrict to these biomes.
structures	string list	[] (any)	Restrict to vanilla structures, in NamespacedKey format.
y_range	int list [min, max]	[-64, 320]	Valid Y range.
light_level_max	int	15	Only spawn where the light level is at or below this value.
time_of_day	string	any	any / day (in-game time 1000–12999) / night (13000–999). Unknown values behave like any.
require_surface	boolean	false	Require full sky light at the spawn position.
distance	{min, max}	{16, 64}	Spawn distance from the player (blocks).
max_nearby	int	0	Max same-id mobs within 64 blocks; 0 = unlimited.
max_global	int	0	Global cap on same-id mobs across all worlds; 0 = unlimited.
count	{min, max}	{1, 1}	Number of mobs to spawn per trigger.
condition	section	none	Optional condition block.

---

Six spawn types

natural — intercept vanilla spawn event

Intercepts Minecraft's CreatureSpawnEvent and replaces naturally spawning mobs with a custom mob when conditions are met.

Field	Type	Default	Description
worlds	string list	[] (any)	Restrict to these world names.
biomes	string list	[] (any)	Biomes where replacement is attempted.
y_range	int list [min, max]	[-64, 320]	Valid Y coordinate range.
light_level_max	int	15	Max light level (inclusive) that allows replacement.
replacement_chance	double	1.0	Probability to replace the vanilla mob.
max_nearby	int	0	Max same-id mobs within 64 blocks; 0 = unlimited.
count	{min, max}	{1, 1}	Number of mobs to spawn per trigger.
condition	section	none	Optional condition block.

- mob_id: elite_zombie
  type: natural
  biomes: [plains, forest]
  y_range: [-64, 50]
  light_level_max: 7
  replacement_chance: 0.08
  max_nearby: 3
  count: { min: 1, max: 1 }

---

structure — timed spawn inside structures

Periodically spawns mobs inside vanilla structures when a player is nearby.

Field	Type	Default	Description
structures	string list	[]	Target structure NamespacedKeys.
max_nearby	int	0	Max same-id mobs near the structure.
active_spawn.interval_ticks	int	1200	Spawn check interval (ticks).
active_spawn.require_player_nearby	int	64	Player proximity required to trigger.

- mob_id: bone_lord
  type: structure
  structures: [minecraft:stronghold]
  max_nearby: 1
  active_spawn:
    interval_ticks: 6000
    require_player_nearby: 64
  count: { min: 1, max: 1 }

---

biome — periodic biome-filtered spawn

Every interval_ticks, searches for a surface position near each online player. Spawns if the position is in one of the listed biomes and meets conditions.

Field	Type	Default	Description
biomes	string list	[] (any)	Target biomes.
interval_ticks	long	400	Check interval per player (ticks).
distance	{min, max}	{16, 64}	Spawn distance from player (blocks).
conditions.light_max	int	15	Max light level at spawn position.
conditions.require_surface	boolean	false	Require sky access at spawn position.
max_nearby	int	0	Max same-id mobs nearby.

- mob_id: jungle_stalker
  type: biome
  biomes: [jungle, bamboo_jungle]
  interval_ticks: 600
  distance: { min: 16, max: 48 }
  conditions:
    light_max: 7
    require_surface: false
  max_nearby: 2
  count: { min: 1, max: 2 }

---

player_relative — follow-player timed spawn

Every interval_ticks, spawns at a random position near each online player. Suitable for rare escort-style mobs.

Field	Type	Default	Description
distance	{min, max}	{16, 64}	Spawn distance from player (blocks).
require_sky_access	boolean	false	Require sky access at spawn position.
max_global	int	0	Global cap on this mob type; 0 = unlimited.
interval_ticks	long	24000	Spawn interval per player (ticks).

---

day_interval — real in-game day timer

Triggers every interval_days in-game days (~20 min/day). Suitable for periodic boss events.

Field	Type	Default	Description
interval_days	int	1	Trigger every N in-game days.
on_day_start	boolean	false	true = trigger at sunrise; false = trigger when counter reaches zero.
distance_from_player	{min, max}	{16, 64}	Spawn distance from player (blocks).
max_global	int	0	Global cap on this mob type.

---

custom — flexible timed spawn

Most flexible type. Periodically spawns near each player, with an optional biome filter.

Field	Type	Default	Description
interval_ticks	long	600	Spawn interval per player (ticks).
distance	{min, max}	{16, 64}	Spawn distance from player (blocks).
biomes	string list	[] (any)	Optional biome filter.
max_nearby	int	0	Max same-id mobs nearby.