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.

U is one of the most generous dragons on Ardeo's scroll. He hardly cares about himself, and seems to be devoted to others. He was named after his parents, I and O.<br/>Even with his outstanding kindness, he's very forgetful. U is often borrowing things such as pretty rocks to look at, and has been caught handing out one or two 'I owe you' notes on small slabs of stone—presumably using his claws to inscribe the rough letters. His mate is a black dragon named Nightlily, who had been hunting down and giving him pretty rocks to gain his attention.