Russet mold was a dangerous fungus found only in places that were dark, warm, and wet. When spread across metal, the mold’s reddish-brown patches could be mistaken for rust, making it difficult to identify without care. Those who strayed too close often suffered as the mold released toxic spores, forcing a creature to endure waves of poison that could quickly overwhelm the unwary. If the victim died, the mold claimed the body as nourishment, and in time Vegepygmies or Thornies emerged from the remains, their entire kind tied to the fungus as both birthplace and sustenance.
Hard to destroy by ordinary means, russet mold resisted weapons and most forms of damage; only acid, necrotic, or radiant power could burn it away, each strike killing it by the foot. Salt or alcohol could scour it in larger patches, and sunlight or curative magic would eradicate it entirely. These weaknesses made the mold survivable, but even a small spread left unchecked could turn caverns or ruins into infested lairs.