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.

Kuroki Heart is the male black dragon chosen to be a mate with Kuro Heart to make baby black dragons and freeze them as hatchlings. Kuro on the other hand feels very awkward about this because Kuroki looks so much younger than her, but goes along with it anyway. Kuroki was meant to be frozen as a hatchling along with the other grass dragon, but was chosen to be a mate for Kuro. The two do love each other, and the gray dragon Haiiro Heart is a good friend of them.

A new drama has come up in the clan, since it was found out that Mizuiro Heart, a water dragon who takes care of hatchlings, had abused Kuro's friend Guardian Heart to his death. Kuroki usually travels onto Jessica Shiro and Zakera Zero's land to get away from their home, because of Mizuiro. Kuroki has no personal issues with Mizuiro, but thinks it's ridiculous that Mizuiro wanted to raise the baby dragons, but then torture them.