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 a different type of mana, making them powerful magic users. Thalassas are a unique variety of Xenowyrm in that they are the only subspecies known to dwell in marine environments. Their porous skin and slender build are perfectly suited for the aquatic terrain, but they can only survive for short periods of time on land. Powerful users of water magic, they can create large waves and alter currents with a simple thought.

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.

Nereus Alexander's duty, like the other Thalassas in his clan, is to ensure that enemies cannot invade through the oceans, seas or rivers to his clan's territory while making sure that his clan can easily travel to enemy territory for raids and battles. Nereus, being highly intelligent, has invented a complex labyrinth system with strong currents that ensures that his clan can easily travel through the waters while keeping strangers out. Nereus has taught this system to his clan, so anyone not familiar with the labyrinth will be lead to deadly currents and forced to drown. Nereus in general is gentle and honest, he tends to be down-to-earth for everything. Nereus rigorous careful work attitude wins him the trust from his clan. Nereus unfortunately can be a workaholic. The other Thalassas that share his duty often force him to relax as they care for his well-being. Nereus has a dry sense of humor and loves to banter. Nereus isn't creative in the artistic sense but highly inventive.