Avatar: The Last Airbender

Long ago, the four nations based on each of the four primary elements--water, air, fire, and earth--lived in harmony. Then one day, the fire nation attacked all the other nations. Only the Avatar, the master of all four elements, could bring back the balance. But just when the world needed him most, he mysteriously vanished. One hundred years later, a waterbender named Katara and her brother Sokka found a strange 12-year-old boy encased in ice. He is Aang, the reincarnation of the Avatar. Unfortunately in his immature, youthful state, he has a lot to learn about his powers and his destiny to save the world.