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.

Marisa Kirisame is a female Deep Sea dragon who enjoys certain activities that many other Deep Sea dragons don't. Though she demonstrates the exemplary traits of a typical Deep Sea dragon, she is quite brutish and tenacious, even willing to physically challenge other naval dragons. This seems to show best when she is met with a confrontation. She would never back down, even if the odds seemed to be against her, earning her many victories in fights.

Occasionally, Marisa and her companions organize an event, which involves a somewhat large gathering of marine dragons commencing in a casual brawl with one another once a year, far beneath the surface of the ocean. She seems to excel at this, and constantly brags about it whenever other dragons question her regarding her physical prowess.