Mushroom Fields

Mushroom fields are a very rare lush biome, and is the rarest non-variant biome in the game (the overall rarest being the modified jungle edge biome) The mushroom biome usually generates as a single island surrounded by ocean, though occasionally generates touching land, and very rarely generates completely landlocked. 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 blocks on the surface. Any grass blocks that are placed by the player in this biome, however, take on a bright green color, similarly to the grass found in jungles. A large amount of brown and red mushrooms cover the mycelium. It is one of the only biomes where huge mushrooms generate naturally, aside from dark forests and swamps $$. The mushrooms generate as trees with a density high enough to be a reliable source of huge mushroom blocks, but low enough not to significantly obstruct vision. Here, mushrooms can grow in full sunlight. Water is a light gray color $$. No mobs other than red mooshrooms spawn naturally in this biome, including the usual night-time hostile mobs; this is also the only biome where mooshrooms can spawn. This also applies to caves, mineshafts, and other dark structures, meaning exploring underground is mostly safe. However, spawners will still spawn mobs, raids still can spawn raiding illagers, wandering traders along with trader llamas can still spawn here, bats will spawn normally, and the player will still be able to breed animals and spawn mobs using spawn eggs; additionally, lightning strikes in this biome still carry the small chance of spawning skeleton traps, and will transform red mooshrooms into brown mooshrooms or vice versa. Phantoms will still spawn in the sky if the player has forgone sleeping for at least 3 in-game days, but a group of phantoms will only spawn if the player leaves the mushroom fields biome(at least one block).

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

Mushroom Field Shore
The mushroom field shore is a technical biome, that represents both the shores and the rivers of the mushroom fields. It generates when a river cuts through it as well as when it borders an ocean, 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 mushroom fields, though it is equal to it in every other way. Buried treasure can generated here and sometimes shipwrecks.