Shadow Walkers are a strange breed that possess the ability to slip between the planes of reality, becoming immaterial. This allows them to hide in the shadows, either hunting from the concealment of near invisibility or evading enemies. Though they become corporeal to mate or to eat, they spend most of the rest of their lives walking in the shadows. Shadow Walkers are wary creatures, though on dark autumn evenings when the leaves fall to swirl in the chill, rain damp air, they may be seen drifting out from the shadows.

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.

Maribel was raised by a clan of normal dragons who had never heard of Shadow Walkers. As a result, she is ignorant of her power to phase through planes of reality, and when she unconsciously uses it, she doesn't recognize what she's doing, instead believing herself to be dreaming. Maribel is always scared that she'll be considered insane as a result of her 'dreams', and the only dragon that she ever talks with about her strange experiences is her Black dragon mate, Renko Usami. She met him as he was wandering in search of books, and found his intelligence and enthusiasm irresistible. She clings to him for support, worried that if she ever gets too lost in a dream, she won't be able to come back and see him again.