A century before the opening story of this series, Aang, a young male driver 12-year-old wind from the South Air Temple owned the Air Nomads, was told by the elders that he was "the Avatar". Usually, the Avatar was told his true identity as the Avatar when he turned 16 years old, however, the monks feared that a war will occur between the four nations is imminent and soon the Avatar would be required to maintain balance and peace of the world. This makes Aang very confused and depressed. Long story short, Aang fled from Southern Air Temple, but in the middle of the road he met a very big storm and he and Appa (giant flying bull owned) fell sunk into the sea. But Aang soon make a ball of air around the body and Appa that he did not get wet. Air ball is frozen water around so that Aang and Appa trapped in the ice.
In the episode "The Boy in the Iceberg," two teenagers from the Southern Water Tribe named Katara - a controller of water - and his brother named Sokka, find Aang in an iceberg, and then they release him. Then from their explanations, Aang knew that as long as he disappeared, the monks fear the war will have become reality. Many years during his escape, the Fire Nation into the homes of controlling the fire, a storm of war three other nations, the Earth Kingdom, Water Tribe, and the Air Nomads. The whole air of the temple was destroyed, including the Air Nomads, they were slaughtered so that Avatar could not be reincarnated. That caused Aang to be the last air controllers on earth. An obligation to study the control of four elements, in order to defeat the Fire King and bring back peace and harmony on earth. To take on the task, accompanied by Katara Aang and Sokka, along with two pets - Momo and Appa - to seek expert control elements, and learn to become an Avatar, and at the same time they must avoid capture by the efforts of State Fire .