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.

We know very little about the Deep Sea Dragons, because they are reserved and shy creatures who prefer swimming in the dark depths of the cold seas. Usually they live in herds, but some of them instead prefer to choose a mate and then continue their lives as a couple, on their own. It is also said that they emerge on the surface only during the mating season.

Indeed, many long-time sailors' legends tell about "Neidr Dyfrol", or water snake, which can be seen only during the moonless nights, because the Deep Sea Dragons look-like remembers a lot the big snakes' one.

Goronwy met his Heledd when they were both very young hatchlings, but he immediately fell in love with hers luminescent scales. He asked her to go together forever and she accepted, now they always swim close to each other and never think of leaving.