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.

Pondfin leads a lonely life, isolated from all the other dragons for the majority of her days. To try and alleviate this loneliness, she visits the surface world frequently, turning off her bioluminescent dorsal fin as to better perceive the other dragons under Nii-Chan's care. Pondfin spends a lot of time with her equals, the other aquatic dragons. They all have a form of symbiosis: Pondfin teaches them how to swim to deeper depths, and they (particularly Aquine) help her tolerate the surface world. This does not completely remove her longing for a companion just like her, one who can share the dark ocean depths with her. Thus, Aquatail came around at the perfect time for Pondfin. She still spends time with her friends on the surface world, but any outside observer could easily say Aquatail is her life now.