Avatar the last airbender book 1 & 2

A century prior to the series' opening, Aang, a 12-year-old Airbender of the Air Nomad's Southern Air Temple, learned from his monk instructors that he was the Avatar. Usually, the Avatar is told of his true identity only after turning sixteen; however, the head monks feared that a war between the four nations was on the horizon, and that the Avatar would soon be needed to help maintain balance. Shortly thereafter, it was decided that Aang would be separated from his guardian, Monk Gyatso, and sent to the Eastern Air Temple to finish his training.

Confused, frightened, and overwhelmed by all that was happening and the incredible burden of responsibility placed upon him, Aang fled from his home on his Flying Bison Appa. While over the frigid southern ocean, a sudden storm caused Appa to plunge deep into the sea. Unknowingly entering the Avatar State, Aang used Airbending and Waterbending to put himself and Appa into an air bubble. The air bubble quickly froze into a sphere of ice, putting them both into a state of suspended animation.

When the series opens one hundred years later, the Fire Nation is on the brink of victory in its imperialist war. The Water Tribes are in crisis — the Southern Water Tribe's warriors have gone off to war, leaving their home defenseless, and the Northern Water Tribe, though largely intact, is continually on the defensive. The vast Earth Kingdom is now the only true barrier to the Fire Nation's domination, but as the Fire Nation continues to encroach on its borders and conquer its territories, hopes for victory grow bleaker with each passing year.

In the present day, two teenage siblings from the Southern Water Tribe — Katara, a Waterbender, and her brother Sokka — discover and free Aang from his iceberg. Aang soon finds out that in his absence, the war that the monks feared had started. The very year he vanished, the ruthless Fire Lord Sozin took advantage of both the Avatar's absence and the Firebending-enhancing powers of a powerful burning comet to launch a war on the three other nations. To Aang's shock and disbelief, the Fire Nation's opening gambit had been a genocidal assault on the Air Nomads. The Air Temples were stormed and the Airbenders slaughtered in an effort to break the Avatar Cycle, leaving him as the last known Airbender in existence.

As the Avatar, it is Aang's duty to restore harmony and peace to the four nations. Along with his newly discovered friends Katara and Sokka, his Flying Bison Appa and his Winged Lemur Momo, and later the blind Earthbender Toph, Aang travels the world to master all four elements, while evading capture by Fire Nation's banished Prince Zuko and later the ruthless Princess Azula.

Although it takes years of discipline and training to master any one element, Aang must master them all and defeat Fire Lord Ozai by summer's end, when the return of Sozin's Comet will grant the Firebenders the power to finish the war. If these events come to pass, not even the Avatar will be able to restore balance to the world.