Thunder Dragons are the masters of electricity. Their wings gather energy as they soar through the clouds, and when they clap their wings together they can create devastating arcs of lightning. They can stay airborne nearly indefinitely, landing only to sleep and breed; they catch their prey from the air and take moisture from the clouds. A thunder dragon’s roar is considered to be an omen of misfortune.

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.

Arwein was born with too much joy, as she was the first thunder egg her parents had produced, and was doted on by her adoring father. When she hatched, it became clear she was a daddy's girl, as she refused to have anything to do with her mother, seeing skywings as an inferior breed, although she revelled in the superior flying skills she inherited from that side of her family. When she ascended to adulthood, she joined the summoning circle in the Aquarius Clan, her trio being completed by Rhewi and Gwres. Through her father, she became introduced to Marshmallow Virgo, a descendant from some of the oldest and most prestigious dragons in the cave, and with his blessing, partnered him.