Waterhorse Dragons received their name due to their horse-like physique and endearing behavior. They are capable of surviving out of water, and when on land their skin secretes a gelatinous goo to retain moisture. However, their large paddle feet are better suited for swimming, and waterhorse dragons tend to move very awkwardly when on land. Waterhorses are very friendly dragons and enjoy playing with humans.

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.

Cayoi is seen as a jovial and calm dragon, someone who would rather help out someone in need than be the cause of the problem. But really the waterhorse is a very sarcastic and brash being who enjoys confusing and manipulating others. He keeps his darker personality hidden because his tricks and manipulations work best when absolutely no one suspects him. Though Cayoi likes large-scale fun such as subtly instigating wars between dragon clans, he is also content to spread rumors and watch the drama unfold. Cayoi is a favored member of his clan and no one would ever think of getting rid of him; the chirpy waterhorse is always willing to lend a paw and is a good friend to many. If only his clan knew that if they exiled Cayoi, most of their problems would vanish. Cayoi's latest trick is showing Rilliu, a small waterhorse, his true personality and laughing as the terrified hatchling tries to convince everyone that the kindest, sweetest dragon they know is really a just a filthy deceiver.