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.
Magi dragons are, as their name suggests, primarily magic users. They rarely use physical forms of attack. They eat anything they can kill, which is almost everything. They won’t kill unprovoked except when hunting, although they may kill humans if in danger. Their strong magic makes them one of the most feared breeds of dragons.
Gandalf was sent by the same order of magi dragons as Saruman to study with Delirium. At first he didn't want to go, because he loved his home and was a bit afraid to move to a new and alien place. But he is no coward and soon he embraced his new life. He isn't the greatest of mages, his only real talent being fireworks and associated spells - like sparking a flame or summoning a light - but he is a good, well-meaning dragon and it's good to have him around.
He spends lots of his day wandering through the lands his new clan inhabits, talking to the pygmies and hatchlings and on his wanderings he met his now-best-friend Radagast. Radagast introduced him to his own mate Galadriel and a young dragoness named Gilraen and now Gandalf couldn't be happier that he is one of Delirium's circle.