Minecraft wiki entry for The_Nether, associated text: The Nether features unique cave-like terrain with no sky. Lava and fire are common hazards everywhere in the Nether. Areas distant from the player are shrouded in fog of red or blue. Unlike the Overworld, the shape of the terrain in the Nether is independent of the biome distribution; instead, the biome alters the surface material and adds terrain features to the netherrack terrain.