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.

Two headed dragons are a special breed of dragons. They have two necks, two brains, two mouths, but one stomach and one main body. The two heads usually work together, but there are times when they will fight each other, attacking back and forth. They use their sharp teeth and wings to hunt large animals, and rarely eat plants. It is unknown what would happen if a two headed dragon were to mate with a one headed dragon, since it has never occurred. They only mate within their breed.

Yinai likes to plan his huntings. The heads talk for a long time, discussing the best way to do what he needs to get his food. It used to happen that he ends hunting something unplanned because he's hungry and there is no other option to get food.

The main head is this left one and the right one acts as his subordinate, many times the right one is the one who fights the prey and the left one the first to be served.

Yinai is known by the other two headed dragons as the "Army" because of this, his claws are his weapons, his wings are his vehicle, his right head the Soldier and his left head the great Sergeant.