Mushroom Islands are very rare biomes added in the Beta 1.9 update to Minecraft. They are home to Huge Mushrooms, Mycelium and Mushroom growths. Mushrooms spread more quickly on Mushroom Biomes and can grow in broad daylight. The island (or very rarely attached to land) biome can have ore, generated structures, and other spawned things that can be in the rest of the world. These are safe places to spend the night (unless close to another biome) because hostile mobs (aside from spawners, spawn eggs, and sieges) cannot spawn in Mushroom Biomes. Sieges are the only natural method of hostile mob spawning. Though Endermen can teleport here and Withers/Bats/Ghasts can fly here, they cannot spawn here.