Brown mold

Brown mold was a variety of fungus that grew in response to warmth. So extremely did it absorb heat that it produced an area of cold around it.

Description
Brown mold often grew in subterranean or dungeon environments in large patches of about in diameter. A patch of this size absorbed enough heat to cool the temperature of the air within a radius. Within of the patch of mold, it was cold enough to cause non-lethal injury to some creatures.

Brown mold grew extremely quickly when exposed to great sources of heat such as a nearby flame, doubling in size in only a matter of seconds. In contrast, the mold could be annihilated almost immediately by the effects of a spell dealing cold damage They were also known to be vulnerable to high concentrations of sunlight or ultra-violet light.

Usage
Besides its natural existence as a dungeon hazard, some found practical uses for brown mold, such as using it to cool food pantries, as was done in the Cathedral of Emerald Scales in Hlondeth. In the House of the Moon in Waterdeep, a small brown mold colony was carefully maintained in a sealed barrel in a small pit in the center of a pantry, kept safely under a locked grate to keep people more than  way. A sign on the door forbade anyone taking fire or any other heat source inside.

Brown mold was also created by the spell mold touch, which was a unique spell available to followers of nature deities Eldath, Mielikki, and Silvanus.

Rumors
The mind flayers were rumored to have developed varieties of brown mold that continued to cool the vicinity around them without harming other life. These varieties were said to grow on illithid homeworlds.

Appearances

 * Adventures
 * Nightmare Keep • The Ruins of Undermountain II: The Deep Levels • Undermountain: Maddgoth's Castle • Curse of Strahd • Waterdeep: Dungeon of the Mad Mage
 * Magazines
 * Dungeon #21, "Jammin" • Dungeon #67, "Training Ground"
 * Card Games
 * AD&D Trading Cards