Rock Wurms are massive worm-like creatures which carve out subterranean caverns. As larvae they secrete an adhesive which binds a layer of rock to them that acts like an armored shell. As they grow older the rock then bonds to their skin permanently. Periodically they creatures must shed their skin, after which the wurm must procure a new rock shell. Rock worms eat and excrete soil, living off the nutrients and biota contained within. Older adults can reach a truly massive size of 300 feet or more.