Entity Random Spawn

Requires ItemsAdder 4.0.11 or greater!

You can make custom entities randomly spawn in your world, exactly how vanilla mobs do.

This is an example to make an example red_zombie spawn.

It will spawn only with a 20% chance of when a vanilla zombie spawns. It will replace the vanilla zombie with the custom one.

It will spawn only in worlds of which name starts by world, between world height 0 and 150 during weather RAIN and with light level from 0 to 10.

info:
  namespace: test
entities:
  red_zombie:
    model_folder: entity/red_zombie
    can_sun_burn: false
    type: ZOMBIE
entities_populators:
  red_zombie_1:
    entity: test:red_zombie
    spawn_logic:
      method: REPLACE # or SPAWN_NEAR
      types:
      - ZOMBIE
    chance: 20.0
    amount: 1
    worlds:
    - world*
    # you can also use x and z as location_range parameters, for example
    # to make edge of the worlds harder with more dangerous mobs
    location_range:
      y:
        min: 0
        max: 150
    weather:
    - RAIN
    light_level:
      min: 0
      max: 10

All properties

entities_populators:
  red_zombie:
    entity: test:red_zombie
    # This sets how to actually spawn the entity. 
    # You can replace a vanilla mob when it's spawned or spawn your mob near it.
    # Note: This uses the Minecraft spawn logic, so gemerule `doMobSpawning false` 
    # will make this stop working.
    spawn_logic:
      method: REPLACE # or SPAWN_NEAR
      types:
      - ZOMBIE
    chance: 20.0
    amount: 1
    # Optional
    biomes:
    - FOREST
    - JUNGLE
    worlds:
    - world
    - "!banned_other_world"
    - "test_world_*"
    # you can also use x and z as location_range parameters, for example
    # to make edge of the worlds harder with more dangerous mobs
    # Optional
    location_range:
      y:
        min: 25
        max: 45
    # Optional
    weather:
    - CLEAR
    - RAIN
    - THUNDER
    - SNOW
    # you can create more intervals, this is useful 
    # to introduce dynamicity to your gameplay
    # Optional
    time:
      interval_1:
        min: 12000 # sunset. also supports the 'sunset' word directly
        max: 23000 # sunrise. also supports the 'sunrise' word directly
    # Optional
    light_level:
      min: 0
      max: 5

Example pack

https://www.spigotmc.org/resources/vanillaex-custom-mobs-pack.125684/www.spigotmc.org