Biomes are one of the main concepts of Reus. Each one of the four Giants can create a unique biome, with the exception of the Rock Giant, which creates both mountains and deserts. There is also a sixth biome, the wasteland, which covers the entire planet at the beginning of every era.
Wasteland tiles cover the planet at the start of each game. It is the only biome which cannot support any natural sources, and only Mountains and Oceans may be created on a Wasteland tile.
Oceans are created by the Ocean Giant on any tile. Once placed, they water Wasteland tiles on either side, allowing Forests and Swamps to be created. Desert in the watered range is converted to Forest.
Mountains are created by the Rock Giant on any tile. Mountains rise and create Deserts on surrounding non-watered Wasteland tiles. They can also be used to cancel out oceans.
Forests are created by the Forest Giant on tiles watered by a nearby ocean. Villages may be founded on Forest tiles near natural sources.
Swamps are created by the Swamp Giant on tiles watered by a nearby ocean. Villages may be founded on Swamp tiles near natural sources.
Deserts occur on non-watered Wasteland spaces when the Rock Giant raises a mountain nearby. Villages may be founded on Desert tiles near natural sources.