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.

Rasunkui's egg was laid near the shoreline of the San'ui Ocean, on a day that was foggy and cold. The Uncita clan took his egg to keep him warm, but when Rasunkui hatched, he ran away back to the beach. It took a search party sixteen days to find him, and when they found him, he was already an adult. Rasunkui claimed that he was turned into an adult by a Magi Dragon. He also said that he touched a piece of gold in the water. Rasunkui is a dragon that is smart enough to make things seem real. He didn't actually touch a piece of gold: just a yellow rock. Like most clever dragons, Rasunkui only breeds with females that believe his stories. He's not a show-off, just a bragger.