The series takes place in a world divided into four nations: the Water Tribes, the Earth Kingdom, the Fire Nation, and the Air Nomads. The Fire Nation has been at war with the other three nations for 100 years, and the Air Nomads have been nearly exterminated. Aang, the reincarnation of the Avatar, a powerful being who can control the four elements, has been frozen in an iceberg for 100 years. He is discovered by Katara, a Waterbender, and her brother Sokka, a non-bender, who help him escape.