Deep Sea Dragons, as their name suggests, spend most of their time in the darkest depths of the sea. They have a bioluminescent dorsal spine that serves to attract prey and communicate with their own kind. As with many deep sea animals, they generally eat whatever they can manage to bait. They rarely leave the ocean floor, surfacing only during breeding season. When they do choose to travel to the shallower depths, they avoid bright lights and will only come up far away from shore.

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.

Hatched and raised by his master, Suki, and clan leader, Hevin, Fukai swims on the ocean floor, traveling alongside his land, sea, and sky-bound clan, signaled by Kagerou and his girl child, Vague, by their swimming down to him and communicating which direction the clan is traveling. A generally content dragon, he, more than most, swims mid-ocean, attracting, killing, and eating much more prey than a majority of the other deep sea dragons can scavenge.

A Japanese dragon named for his habitat, Fukai En'you means 'Deep Ocean.'