Dragons are creatures with nearly unlimited life spans. They can survive for long periods of time, and no one has found a dragon that has died of old age. Adolescence 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. Once they hit adolescence, hatchlings change quickly, maturing to their full forms in only 2 years.

Dragons don't communicate with each other verbally, but they will growl to scare off predators and frighten prey. Young dragons will emit an extremely high-pitched squeal when they are frightened. To communicate, they use telepathy with each other and to speak to other creatures.

Black dragons are warriors. They are strong and capable in battles of force, but also ample magic users, capable of devastating opponents with their spells. Their bright eyes give them excellent night vision, which is why they generally hunt during the night.

Bikou is an energetic and restless soul who is the best friend and soul-mate of the only dragon who is able to calm his spirit, Setsuna. When she is out hunting, Bikou is always either swimming with the water dragons in the Guardian Lake, excavating the tunnels beneath and inside the main caves to make room for more dragons with the vines or flying patrol with the storms and skywings. When Setsuna comes home, these two fierce fighters are nearly inseparable.