Regions contain all per-region settings such as biome placement, which land-, sea-, and shoreBiomes spawn, and much more. You find & create regions in the 'regions' folder.


    "name": "Plains",
    "landBiomes": ["plain"],
    "seaBiomes": ["plain"],
    "shoreBiomes": ["plain"]

Regions are mainly a gateway to / collection of biomes. This is also why they are quite simple to set-up.

name is the name of the region when it is ever displayed. This does not have to equal the name of the file, but it is recommended to be at least similar so you can find region back more easily.

land-,sea- and shorebiomes are the three parts that make up any Iris world. land biomes are all biomes that spawn above land, apart from the shore biomes that spawn next to the sea biomes. See Shore Ratio.

5 Elements

Five other settings that you will likely need when setting up a region are:

    "blockDrops": [],
    "entitySpawners": [],
    "jigsawStructures": [],
    "rivers": true,
    "riverChanceStyle": {},
    "riverRarity": 0,
    "riverStyle": {},
    "riverThickness": 0,
    "shoreRatio": 0

Block Drops

blockDrops allow you to replace blocks that are dropped with another block. This setting is also available in Biomes & Dimensions.

Entity Spawners

entitySpawners allow you to place Entities & Spawners in your worlds. This setting is also available in Biomes & Dimensions.

Jigsaw Structures

jigsawStructures allow you to place jigsaw structures in this region. You set a rarity (the 1 in x chance to spawn), and a structure which directly references a Jigsaw structure. This setting is also available in Biomes & Dimensions.


rivers, riverChanceStyle, riverRarity, riverStyle and riverThickness allow you to create rivers in your regions. You can also use fluidBodies for this, which is likely more efficient and perhaps better-looking. FluidBodies place rivers & lakes through a terrain modification, whereas Rivers do so by pulling down the terrain height abruptly in certain locations.

Shore Ratio

shoreRatio lets you define how "wide" shorelines are. If you set this to 1, only shore & sea biomes will spawn, and all land will be shoreline.

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