Entity Spawners Guide

Entity spawners control how mobs and creatures populate your Iris worlds. Unlike vanilla spawning, Iris spawners are persistent and continually replenish entities.

What is an Entity Spawner?

An Iris spawner defines:

What entities spawn
Where they spawn (biome types, light levels, time)
How often they spawn (rates, cooldowns)
Initial spawns vs. continuous spawning

Spawners can be referenced by dimensions, regions, and biomes.

Creating a Spawner

Create the JSON file

Create a file in spawners/ folder:

{
  "spawns": [
    {
      "entity": "zombie",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.5
    },
    {
      "entity": "skeleton",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.3
    }
  ],
  "maxEntitiesPerChunk": 8,
  "allowedLightLevels": {
    "min": 0,
    "max": 7
  }
}

Reference in configs

Add to dimension, region, or biome:

{
  "entitySpawners": ["hostile-mobs", "passive-animals"]
}

Test in-game

Explore your world and observe entity spawning behavior.

Spawner Configuration

Basic Properties

Field	Type	Default	Description
`spawns`	Spawn[]	-	List of entity spawns (required)
`initialSpawns`	Spawn[]	[]	Spawns that happen once per chunk
`maxEntitiesPerChunk`	Integer	1	Max entities before spawner pauses
`energyMultiplier`	Double	1.0	Energy cost multiplier

Spawn Groups

Control where spawners activate:

{
  "group": "NORMAL"
}

Options:

NORMAL: Land biomes only
UNDERWATER: Ocean biomes only
BEACH: Shore biomes only
CAVE: Cave areas

Time Restrictions

{
  "timeBlock": {
    "minTime": 13000,
    "maxTime": 23000
  }
}

Only spawn during these Minecraft times (0-24000):

Day: 0-12000
Sunset: 12000-13000
Night: 13000-23000
Sunrise: 23000-24000

Weather Restrictions

{
  "weather": "RAIN"
}

Options:

ANY: Any weather
CLEAR: Clear weather only
RAIN: Rain/snow only
THUNDER: Thunderstorm only

Light Level Restrictions

{
  "allowedLightLevels": {
    "min": 0,
    "max": 7
  }
}

Only spawn in light levels 0-15 (0 = dark, 15 = bright).

Spawn Rates

Global rate limit:

{
  "maximumRate": {
    "interval": 200,
    "count": 5
  }
}

interval: Ticks between spawn attempts
count: Max spawns per interval

Per-chunk rate limit:

{
  "maximumRatePerChunk": {
    "interval": 600,
    "count": 2
  }
}

Entity Spawn Configuration

Basic Entity Spawn

{
  "entity": "cow",
  "minAmount": 2,
  "maxAmount": 4,
  "chance": 0.5
}

Field	Type	Description
`entity`	String	Entity type (required)
`minAmount`	Integer	Minimum entities to spawn
`maxAmount`	Integer	Maximum entities to spawn
`chance`	Double	Spawn probability (0-1)

Entity Types

Use Minecraft entity IDs: Passive:

cow, sheep, pig, chicken
horse, donkey, mule, llama
cat, ocelot, parrot, wolf
rabbit, fox, bee, turtle
villager, wandering_trader

Hostile:

zombie, skeleton, creeper, spider
enderman, witch, slime
phantom, drowned, husk, stray
pillager, vindicator, evoker

Nether:

zombified_piglin, piglin, hoglin
blaze, ghast, magma_cube
wither_skeleton, strider

Aquatic:

cod, salmon, tropical_fish, pufferfish
squid, glow_squid, dolphin
guardian, elder_guardian

Custom Entity Data

Baby entities:

{
  "entity": "zombie",
  "baby": true
}

Named entities:

{
  "entity": "sheep",
  "customName": "Fluffy"
}

Villager professions:

{
  "entity": "villager",
  "profession": "farmer"
}

Example Spawners

Passive Animals

{
  "spawns": [
    {
      "entity": "cow",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 0.4
    },
    {
      "entity": "sheep",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 0.4
    },
    {
      "entity": "pig",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.3
    },
    {
      "entity": "chicken",
      "minAmount": 2,
      "maxAmount": 6,
      "chance": 0.5
    }
  ],
  "initialSpawns": [
    {
      "entity": "cow",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 1.0
    },
    {
      "entity": "sheep",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 1.0
    }
  ],
  "group": "NORMAL",
  "maxEntitiesPerChunk": 12,
  "allowedLightLevels": {
    "min": 0,
    "max": 15
  },
  "maximumRate": {
    "interval": 400,
    "count": 3
  }
}

Hostile Mobs

{
  "spawns": [
    {
      "entity": "zombie",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.5
    },
    {
      "entity": "skeleton",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.4
    },
    {
      "entity": "creeper",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.3
    },
    {
      "entity": "spider",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.3
    },
    {
      "entity": "enderman",
      "minAmount": 1,
      "maxAmount": 1,
      "chance": 0.1
    }
  ],
  "group": "NORMAL",
  "maxEntitiesPerChunk": 8,
  "allowedLightLevels": {
    "min": 0,
    "max": 7
  },
  "timeBlock": {
    "minTime": 13000,
    "maxTime": 23000
  },
  "maximumRate": {
    "interval": 300,
    "count": 2
  }
}

Ocean Life

{
  "spawns": [
    {
      "entity": "cod",
      "minAmount": 3,
      "maxAmount": 8,
      "chance": 0.6
    },
    {
      "entity": "salmon",
      "minAmount": 2,
      "maxAmount": 5,
      "chance": 0.4
    },
    {
      "entity": "tropical_fish",
      "minAmount": 4,
      "maxAmount": 12,
      "chance": 0.3
    },
    {
      "entity": "squid",
      "minAmount": 1,
      "maxAmount": 4,
      "chance": 0.4
    },
    {
      "entity": "dolphin",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.1
    }
  ],
  "group": "UNDERWATER",
  "maxEntitiesPerChunk": 15,
  "allowedLightLevels": {
    "min": 0,
    "max": 15
  },
  "maximumRatePerChunk": {
    "interval": 600,
    "count": 5
  }
}

Desert Creatures

{
  "spawns": [
    {
      "entity": "rabbit",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.3
    },
    {
      "entity": "husk",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.4
    }
  ],
  "initialSpawns": [
    {
      "entity": "rabbit",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 1.0
    }
  ],
  "group": "NORMAL",
  "maxEntitiesPerChunk": 6,
  "allowedLightLevels": {
    "min": 0,
    "max": 15
  }
}

Cave Dwellers

{
  "spawns": [
    {
      "entity": "zombie",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.5
    },
    {
      "entity": "skeleton",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.4
    },
    {
      "entity": "spider",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.3
    },
    {
      "entity": "bat",
      "minAmount": 2,
      "maxAmount": 5,
      "chance": 0.4
    }
  ],
  "group": "CAVE",
  "maxEntitiesPerChunk": 10,
  "allowedLightLevels": {
    "min": 0,
    "max": 7
  },
  "maximumRate": {
    "interval": 400,
    "count": 3
  }
}

Nether Spawner

{
  "spawns": [
    {
      "entity": "zombified_piglin",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 0.5
    },
    {
      "entity": "piglin",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.3
    },
    {
      "entity": "hoglin",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.2
    },
    {
      "entity": "magma_cube",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.3
    },
    {
      "entity": "blaze",
      "minAmount": 1,
      "maxAmount": 1,
      "chance": 0.1
    }
  ],
  "maxEntitiesPerChunk": 10,
  "allowedLightLevels": {
    "min": 0,
    "max": 15
  },
  "maximumRate": {
    "interval": 300,
    "count": 3
  }
}

Jungle Wildlife

{
  "spawns": [
    {
      "entity": "parrot",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.4
    },
    {
      "entity": "ocelot",
      "minAmount": 1,
      "maxAmount": 1,
      "chance": 0.2
    },
    {
      "entity": "panda",
      "minAmount": 1,
      "maxAmount": 2,
      "chance": 0.15
    },
    {
      "entity": "chicken",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 0.3
    }
  ],
  "initialSpawns": [
    {
      "entity": "parrot",
      "minAmount": 2,
      "maxAmount": 4,
      "chance": 1.0
    }
  ],
  "group": "NORMAL",
  "maxEntitiesPerChunk": 8,
  "allowedLightLevels": {
    "min": 0,
    "max": 15
  }
}

Night Phantoms

{
  "spawns": [
    {
      "entity": "phantom",
      "minAmount": 1,
      "maxAmount": 3,
      "chance": 0.3
    }
  ],
  "maxEntitiesPerChunk": 4,
  "timeBlock": {
    "minTime": 13000,
    "maxTime": 23000
  },
  "allowedLightLevels": {
    "min": 0,
    "max": 15
  },
  "maximumRate": {
    "interval": 1200,
    "count": 1
  }
}

Energy System

How Energy Works

Spawners consume “energy” to prevent infinite spawning:

Dimension has max energy pool (default: 1000)
Each spawn attempt costs energy
Energy regenerates over time
When energy is depleted, spawning pauses

Energy Configuration

In dimensions:

{
  "infiniteEnergy": false,
  "maximumEnergy": 1000
}

In spawners:

{
  "energyMultiplier": 1.5
}

Higher multiplier = more energy cost = less frequent spawning.

Infinite Energy

{
  "infiniteEnergy": true
}

Disables energy system. Not recommended - can cause lag from excessive spawning.

Spawner References

In Dimensions

{
  "entitySpawners": ["passive-animals", "hostile-mobs"]
}

In Regions

{
  "entitySpawners": ["desert-creatures", "common-hostiles"]
}

In Biomes

{
  "entitySpawners": ["jungle-wildlife", "tropical-fish"]
}

Tips & Best Practices

Balance Entity Counts

Passive mobs: 8-15 per chunk
Hostile mobs: 5-10 per chunk
Rare creatures: 1-3 per chunk

Use Initial Spawns

Add initialSpawns for immediate population:

{
  "initialSpawns": [
    {
      "entity": "cow",
      "minAmount": 4,
      "maxAmount": 8,
      "chance": 1.0
    }
  ]
}

Layer Multiple Spawners

Combine spawners for variety:

{
  "entitySpawners": [
    "base-animals",
    "rare-wildlife",
    "ambient-creatures"
  ]
}

Match to Environment

Light levels: Dark for hostiles, any for passive
Groups: Underwater for fish, normal for land
Time: Night for hostiles, any for passive
Weather: Thunder for special events

Prevent Lag

Use reasonable maxEntitiesPerChunk
Set appropriate spawn rates
Don’t use infiniteEnergy unless testing
Consider energyMultiplier for balance

FAQ

Why aren't entities spawning?

Check:

Light levels match allowedLightLevels
Time is within timeBlock range
Weather matches weather setting
Biome type matches group
Energy isn’t depleted (check infiniteEnergy)
maxEntitiesPerChunk not exceeded

What's the difference between spawns and initialSpawns?

initialSpawns execute once when a chunk is first generated. spawns continue to replenish entities over time.

Can I spawn modded entities?

Yes, if the mod properly registers entities with Bukkit/Spigot. Use the entity’s namespaced ID.

How do I make boss mobs spawn?

Use very low chance (0.001-0.01), high energyMultiplier, and strict conditions (time, weather, light).

Why do I have too many entities?

Lower maxEntitiesPerChunk, reduce chance values, increase spawn interval, or raise energyMultiplier.

Next Steps

Configure Biomes for appropriate spawner groups
Create Loot Tables for mob drops
Design Regions with themed wildlife

Getting Started

Core Concepts

World Generation

Content Creation

Advanced Features

Commands

​What is an Entity Spawner?

​Creating a Spawner

​Spawner Configuration

​Basic Properties

​Spawn Groups

​Time Restrictions

​Weather Restrictions

​Light Level Restrictions

​Spawn Rates

​Entity Spawn Configuration

​Basic Entity Spawn

​Entity Types

​Custom Entity Data

​Example Spawners

​Passive Animals

​Hostile Mobs

​Ocean Life

​Desert Creatures

​Cave Dwellers

​Nether Spawner

​Jungle Wildlife

​Night Phantoms

​Energy System

​How Energy Works

​Energy Configuration

​Infinite Energy

​Spawner References

​In Dimensions

​In Regions

​In Biomes

​Tips & Best Practices

​Balance Entity Counts

​Use Initial Spawns

​Layer Multiple Spawners

​Match to Environment

​Prevent Lag

​Next Steps

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