Toadstools (unofficial name) are obstacles placed around some Floors. Like Rocks, they occupy one square and block tears (except for Spectral Tears) or movement through them. They are only found in The Binding of Isaac:Rebirth
They can be destroyed by any kind of explosion. When destroyed, they sometimes release a skull-shaped gas cloud that can damage the player, or sometimes contain a pill, a tarot card, a suit card, Liberty Cap trinket, or a Magic Mushroom.