One hundred years before the story begins, a twelve-year-old Airbender named Aang learns that he is the new Avatar. He is not happy when he learns this, because he knows that being the Avatar is a big responsibility, and he does not think he is ready for it. He is also scared of having to leave his mentor, Monk Gyatso, whom he loves very much. Aang flees from home on his animal guide, a flying bison named Appa. But they fly into a big storm and crash into the ocean, and Aang goes into the Avatar State and freezes himself and Appa inside an iceberg. They are frozen in a state of suspended animation—they cannot move, grow older, or die. While this is happening, the Fire Nation is beginning a war against the other three nations. Fire Lord Sozin, the leader of the Fire Nation, knows that the new Avatar is an Air Nomad (because of the Avatar Cycle's pattern), so he kills all of the Air Nomads in a genocide. This is because he wants to make sure that the Avatar, who is very powerful, will not be able to defeat the Fire Nation in the war. The FIre Nation army is able to kill all of the Air Nomads because a comet called "Sozin's Comet" made their bending much more powerful. But because the actual Avatar, Aang, is frozen in an iceberg, he is not killed. He is the only Airbender to survive the attack. For one hundred years, everybody in the world believes that the Avatar does not exist anymore.