The Lorekeeper's Tome

The Rock Crawler is the deep-folk's least favourite neighbour: a heavy, boulder-shelled creature of the Iron Hills and the lower caverns, so thickly armored that it can be mistaken for an outcrop of stone until it moves. It is slow and incurious, grinding through the dark on stubby legs, but its shell turns aside pick and blade alike, and breaking one open is the work of patience and a heavy hammer. The dwarves wall them off rather than fight them when they can.