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.

Herulus was the first alternative-form Black dragon to be housed at the Hilltop Mews.  Like many of the dragons in the Hilltop cave complex, he was abandoned as an egg and rescued.  Herulus is unfortunately not the brightest dragon, and this combined with his natural anger makes him difficult to deal with.  He is not permitted out of his cave with the other dragons, and he is kept from breeding with the Hilltop females due to the severe amount of inbreeding in his lineage.