Null caps are a type of fungus which grow underground in caverns such as Corpigras. Nulls caps are bioluminescent. Different species give off different colours of light. There are white, dim yellow, green, orange, pink and lavender varieties. Because of their luminescence, null caps are liked by Tzatti. In fact, Tzatti inadvertently spread null cap spores around, helping to propagate them. Some null cap varieties are poisonous or even bioelectric. The small, pink null caps are very spicy and umami, and go nicely in a stew, stock, soup, or curry.