Druk

Druk is Lord Zuko's dragon, serving both as the retired Fire Lord's mount and animal companion.

History
Zuko traveled with Druk to Ming-Hua's prison after hearing about the waterbender's escape, where he learned about Zaheer's recent acquirement of airbending. Visibly alarmed by this development, Zuko promptly departed on Druk to the Northern Water Tribe, where he and Chief Tonraq informed Chiefs Desna and Eska about an impending attack on P'Li's prison in the western tundras.

Trivia

 * Druk is the only known living dragon in the Avatar World apart from Ran and Shaw.