Brown Mold

Brown mold is a fungus that grows in response to heat. It absorbs heat so quickly that it creates a cold zone around it.
Brown mold grows in large patches of about 10 feet diameter in subterranean or dungeon environments. A patch of this size absorbs enough heat to cool the air within a 30 foot radius. It is cold enough within 5 feet of the mold patch to cause non-lethal injury to some creatures.
When exposed to high heat sources, such as a nearby flame, brown mold grows extremely quickly, doubling in size in a matter of seconds. The mold, on the other hand, can be annihilated almost instantly by the effects of a cold damage spell. They are also known to be sensitive to high levels of sunlight or ultraviolet light.
Aside from its natural existence as a dungeon hazard, some people use brown mold for practical purposes, such as cooling food pantries.
The Illithid are said to have developed brown mold varieties that continue to cool the environment around them without harming other life. These varieties are said to grow in the Undervale's Illithid cities.

Genetic Ancestor(s)

• Ooze