Mushroom Fields

The Mushroom Fields biome is the rarest main biome. It is a lush biome. It is meant to be found fully encompassed by oceans, however sometimes it can generate touching other land biomes. It has only one variant.

Description
Mushroom fields biomes consist of a mixture of flat landscape and steep hills and have mycelium instead of grass on the surface. A large amount of brown and red mushrooms cover the mycelium. It is one of the only biomes where huge mushrooms generate naturally, generating as trees, with a density high enough to be a reliable source of huge mushroom blocks, but low enough not to significantly obstruct vision. Here, mushrooms can grow in full sunlight.

No mobs other than mooshrooms spawn naturally in this biome, including the usual night-time hostile mobs. This also applies to caves, abandoned mineshafts, and other dark structures, meaning exploring underground is supposedly safe. Spawners will still spawn mobs however, and the player will still be able to breed animals and spawn mobs using eggs.

This biome is one of the toughest for survival, especially because of the extreme rarity and non-renewability of wood, abandoned mineshafts which also contain poisonous spider spawners being the only source. Once the first seven wooden planks blocks are gathered however, food is relatively easy to collect, as mooshrooms will produce mushroom stew anytime the player right-clicks them with a bowl.

Lack of mobs also means lack of any mob-related resources, such as wool, string, bones, gunpowder, feathers, spider eyes and ender pearls, some of which have various crucial uses for survival, such as crafting beds, arrows or ender eyes. As an unprepared player cannot make a bed to sleep or bows and arrows to fight, phantoms will likely terminate such a player if they attempt to leave the biome after an extended stay.

Variants
Mushroom fields have only one variant, for a total of two different mushroom fields biomes.

Mushroom Field Shore
Mushroom Field Shore (known as MushroomIslandShore before 1.13) is a technical biome, that represents both the shores and the rivers of the Mushroom Fields biome. It generates when a river cuts through a mushroom fields biome as well as when the mushroom fields biome borders an ocean biome, unless the ocean is a deep variant, in which case a steep cliff will generate instead. The terrain of this biome is much flatter and shallower in elevation than the main mushroom fields biome, though it is equal to the main mushroom fields biome in every other way.