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.

There are a number of stories about what happened to Umadrix's right horn ranging from the mundane—a rock fell and broke it—to the virtually unbelievable—that he defeated a Guardian of Nature in single combat, and there is still a burning ember of raw magic that is eating the horn as fast as it grows. Umadrix tells whatever story he thinks will most impress whatever girl he seeks to woo at any given moment, making him an unreliable source.

Despite being a marrow Umadrix is a very picky eater. He excels at preparing foods solely because if his food isn't just the way he likes it, he won't eat it.

Umadrix's third big interest is fighting. He loves a fair fight against a worthy opponent, and makes a point of offering healing salves after a battle to those whom he respects. He loathes backstabbing and poisons, which he considers to defeat the whole point of battle. The only time he will kill is when threatened by such ignoble foes.