Black Marrows are named for their dark colored hides which are encased in a distinct exoskeleton. Their skull and the top edges of their spine push out from under the skin as they age. As such, their young need excessive amounts of calcium for this armor to develop. The older a Black Marrow dragon is, the more skeletal their appearance. They often use their skeletal looks to lure in foolish scavengers or terrify predators. These vicious dragons love nothing more than to crack open bones with their stony beaks and eat the marrow inside. Voracious scavengers, Black Marrows will swarm and devour corpses both old and fresh, sometimes even dragging larger finds to the water to allow them to “ripen.” Despite their dreadful demeanour and often horrid stench, Black Marrows are devoted mates and parents.

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.

Thanatos' love of corpses gives him a rather distinct, decaying odor about him. Even his tamer has trouble stomaching the smell, but she still treats him as one of her beloved dragons. Very much like Violet Sage of Forest, Thanatos likes to hoard things, though usually his collection consists of exclusively skulls and bones of dead animals. Thanatos helps his tamer by extracting all decaying tissue from skulls and bones so that she can clean them and use them for anatomical studies. He seems to be very proud of his role as her assistant and happily accepts a dead vole or ferret in exchange for his services.