Each Fever Wyvern carries a unique and very deadly disease on the spines of its tail. To make up for a lack of physical strength, the dragons use this disease to their advantage by poisoning prey and fending off attackers. The illness will quickly render victims helpless before eventually killing them. A Fever will track its prey until the target can no longer move. Usually a solitary breed, these dragons will only come together during mating season, and will flare out the brightly colored sails along their wings to help attract potential mates. Although it has been observed that the wyverns are nocturnal, they will often pick an open spot of sunshine to curl up in and sleep as the day passes by.

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.

Gelyan is sometimes accused of being a coward because he doesn't like close combat. When he has to fight, he uses his crossbow—either in his talons while flying, or in his wing-claws while grounded—and a blowdart gun which never leaves his lips. Both weapons bear his tail's miasma. Usually, however, he avoids combat entirely with creative solutions and help from his friends, Neraine and Sisilly. He has a chronic case of Fool's luck that brings trouble to him as much as it saves his tail and often winds up being Hanged upside-down by one ankle. Success, news, and unsavory happenings seem to follow him wherever he goes.

When things inevitably go wrong, Gelyan and his friends work together well, and he trusts them with his life. When away from Neraine, he has called her his girlfriend, though it seems she does not share these sentiments.

There is what seems to be a flat, flying kangaroo that follows Gelyan's commands. Nobody knows what it is, where it came from, nor how(if) it exists.