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.

One of the first things that Kasei did after she hatched was attack the guardian of the eggs, the black dragon named Dark. However, she quickly found herself trapped between the black dragon's claws, much to her surpise. Dark let her go, but always kept a very close eye on her after that.

A unsurprising thing was that that incident made many dragons reluctant to approach her, except for two of them. Dark's mate Allain, and his child Tairgi. Those two purple dragons became Kasei's foster mother and sister, as well as her friends. Tairgi even chose Kasei's name, saying that it meant 'force of flames' according to one of the humans she'd talked to.

Kasei is extremely soft-hearted for a Hellfire Wyvern, mainly because she was raised by Allain. However, she shares the purple dragon's fearless attitude, and will face any dragon with her head held high. She oftens keeps one eye on Tairgi,  even though her little foster sister has constantly pointed out that she can take care of herself.