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.

Keiko is the oldest dragon in her cave and therefore nobody knows her actual age. Having lived for such a long time, she acquired knowledge most dragons dream of. The dragons in her cave sometimes ask her for advice, but only in emergencies, since she lives a hermit's life in the darkest depths of the sea and does not appreciate any intrusion into her placid life.

Mostly, she slumbers at the bottom of the sea, as she is old, even for a dragon. Keiko is not interested in the noisy cave life anymore, believing it is tiring. She rather likes to communicate with small fish who live in the abyss, as she does, since their view of life, as it is short, is far different from a dragon's, since their lifespan is near eternity. They approach her, knowing that she has learnt to live on plankton in order to converse with them.