After a series of misadventures, Aang meets his previous incarnation, Roku, who informs him that he must master all four bending arts and end the war before the coming of Sozin's Comet at the end of summer.After helping the Water Tribe drive off a Fire Nation invasion headed by Admiral Zhao, with Katara as his teacher, Aang and his group journey to the Earth Kingdom to find an Earthbending teacher.But upon learning that he was actually on the back of a Lion Turtle, one of four that made the first benders by manipulating humans' chi, Aang receives the Lion Turtles' Energybending ability.With this ability, as he regained his Avatar State, Aang removes Ozai's bending ability, rendering him harmless and ending the Hundred Year War.The group learns about the Day of Black Sun in a secret underground library, and they attempt to reveal the information to the Earth King at Ba Sing Se.However, their flying bison, Appa, is captured by Sandbenders.
During the finale, finding himself on a strange island, Aang is reluctant to actually kill Fire Lord Ozai, despite his four previous past lives (Roku, Kyoshi, Kuruk, and Yangchen) convincing him it is the only way.
Aang was survived by his wife, Katara, and his three children, but he did not live to see his grandchildren, all of whom would become powerful Airbenders.
Prior to his death, Aang tasked the Order of the White Lotus with finding and guiding the new Avatar after him.
Meanwhile, Fire Lord Ozai is angered that Iroh betrayed the Fire Nation.
So he sent Princess Azula to hunt down Zuko and Iroh.