Originating from a single species that thrived in ancient times, Xenowyrms have become an incredibly diverse breed whose appearances vary depending on their habitats. Each Xenowyrm subspecies is heavily reliant on the power of different types of mana, making them powerful magic users. Astrapi are easily the most temperamental of all Xenowyrm subspecies. Their unpredictable behavior—coupled with their masterful control of lightning magic—has the potential for devastating results. Most of their time is spent airborne, flying through the skies or circling mountainsides for prey.

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.

Aku is pretty irritable in almost every social scenario, whether a large inter-clan festival, a quiet family dinner, or the yearly health checkup with the clan's White Dragons. He has a habit of giving off small bursts of electricity when he is particularly annoyed, but puts this to good use by patrolling the Sylvain clan's mountainous cave territory and zapping away any airborne pests that seek to nest nearby. He's become such a common sight in the sky that some of the hatchlings have taken to following him at a distance, watching him lightning-strike down predatory birds and occasionally entire swarms of insects. Whether he is flattered by the sounds of their whoops and cheers, no one will ever know, but he's never chased off any of his younger siblings.