Hellfire Wyverns are so named for their foul tempers and fiery visages. Their social structure places all females above all males, due to superior physical characteristics and violent dispositions. Forced subservience of the males causes them to become vicious, petty, antisocial, and passive-aggressive compared to the aggressive and social females. However, orphaned hatchlings raised by foster parents of another species can develop surprisingly even tempers and mellow dispositions, proving that their defining unpleasant nature is, in fact, a learned behavior.

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.

Thermadon was one of the first dragons in Belgemine's cave. He's always been sort of cold towards Belgemine and the other Dragons; that is except for Flandragora a young, female Pygmy dragon who had been following him around ever since she was a hatchling. Thermadon and Flandragora soon became friends and he has protected her ever since then. He recently had a child with Dahaka: Mt. Gagazet, who is currently his only child she was frozen... and is not allowed out of the cave Thermadon looks after her and Flandragora since Dahaka is rarely seen on the cave.