After Roku's death, the previous Avatar, the Avatar was reincarnated as an Airbender, named Aang. Because of the threat of a war, Aang learned of his Avatar status when he was only twelve years of age. Aang, terriefied by his new responsibilities and inexpereince was then seperated from his mentor Gyatso. So he fled his home on his flying bison, Appa. They were forced into an ocean by a storm, and with Aang entering the Avatar State he accidently enclosing them both in an iceberg, for one hundred years. The leader of the fire nation knowing the nature of the Avatar's reincarnation cycle, carried out genocide of the Air Nomads during the passing of a comet.