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.

Rei is a dragon with dual personality who are pretty much polar opposite to each other despite having the same name. One of the personality is a very silent, cold and prefer to be left alone as much as possible which makes people think she is emotionless while the other personality is very outgoing, boisterous and prideful, a switch between both personality can easily determined by seeing the color of her eyes as while the first personality possess a pair of blood red eyes, the other possess a pair of cool blue eyes. Funnily, despite the opposing personality, both of them have a crush on the same dragon: Jigokuen. In battle, Rei in able to breath special light blue colored fire which can burn the target without creating any smoke but also extremely hot that there won't even be any ash left.