The Apostate Mushroom can be found only in the Deep Biome. When approached by a player, this mushroom will explode, spewing a puff of deadly gas.
How to Obtain
This gassy 'shroom can be used as decoration, just be sure to enclose it in a box or to keep it out of reach of other players. They will eventually be able usable in Mushroom Wine but that may be a little while off.