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.

Kaito's Judgement Of Corruption, as his name indicates, is the servant of Kaito Lord Of Darkness. However, he is also a full member of the Vocaloids, with songs—and an intriguing backstory—of his own. Rumour has it that Judgement was once an ordinary dragon; ordinary only in breed, however, for he was the dragon responsible for judging those who had been accused of doing wrong and deciding if they were guilty. However, as time passed he grew greedy and corrupt. He began to take bribes of treasure and magic from dragons in return for falsely declaring a suspect innocent or guilty. Eventually, he set a vicious murderer free after being heavily bribed, and the dragons of his Cave rose up against him, killing him and his sick daughter. But there was no end to Judgement's deviousness, the story runs, and he bribed the Master Of Hell to let him return as a Hellfire Wyvern. Some even say that his daughter was reborn as Miku's Game Of Life; the two wyverns are certainly very close.