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.

Like Slyphy and Haku, Lio lives with them within the same ocean, but for whatever reason, hasn't gotten around to visiting either of them. There are always plans to swim over to where his elder siblings are, but there was always something else more interesting to due in his area of the ocean on the day that he planned on visiting. While his elder sister prefers to just watch the phosphorescent coral glow, from time to time Lio takes the fallen pieces of coral back into his underwater cave to decorate it with. While this does make his home more visible to predators-though who would dare antagonize a dragon is anyone's guess- it also makes it more lovely to look at.