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.

Ryoichi has an extraordinary talent. Because of his great strength and the pressure his stone lined talons can exert, he can force lumps of coal into diamonds the size of tangerines. The process takes a long time, as he has to let the heat and pressure grow until the conditions are just right. Should he try too soon the coal will crumble into dust, too long and the diamond will melt from the heat.

His talent is kept secret, lest treasure hunters invade the territory in order to obtain these massive jewels and injure members of the family in their greed.

Though beautiful, the diamonds themselves have no practical use, aside from being added to the hoard, so they are mainly used as toys by the hatchlings, who enjoy using them as giant marbles.