Stone Dragons have a tough outer covering made of a stone-like material. They eat rocks, using the minerals they contain for nourishment and to keep up their stone outer shell. They rarely move, and are the heaviest of all types of dragons. Although they have wings, indicating flight ability, no one has ever seen a stone dragon flying.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

At first glance, one might mistake Obsidian Idol as one of Echidne's statues. A person would probably have to watch for some time before seeing the slight movements that indicate this is a living creature rather than a stone statue. Obsidian Idol stays a ways into the cave, around the area where it splits off into other chambers. She eats the debris that comes from when Antille makes new chambers or when Echidne dislikes how a statue turned out. Other than when eating these rocks, she almost never moves. The last time she was seen moving with any sort of speed was when she snapped at a dog that mistook her for a statue and tried to 'mark' her.