Avatar

"Water. Earth. Fire. Air. Long ago, the four nations lived together in harmony. Then everything changed when the Fire Nation attacked. Only the Avatar, master of all four elements, could stop them, but when the world needed him most, he vanished. A hundred years passed and my brother Sokka and I discovered the new Avatar, an airbender named Aang. Although his airbending skills were great, he had a lot to learn before he was ready to save anyone. But from the first day I met him, I believed Aang would save the world. And you know what? I was right. With the help of his friends, Aang defeated Fire Lord Ozai and ended the Hundred Year War. Zuko, Ozai's son and our ally, became the new Fire Lord. Together with Earth King Kuei, Aang and Zuko promised to return the nations to harmony." —Katara   Avatar takes place in a world that is home to humans and hybrid animals, intersecting with a Spirit World. Human civilization is divided into four mega cultures: the Water Tribes, the Earth Kingdom, the Fire Nation, and the Air Nomads. Each has a distinct society, wherein people known as "benders" can manipulate and control the element of their nation using the physical motions of martial arts. Each region has unique geographical layouts, civilizations, climates, and demography, and each one has a diverse range of land formations.   At the end of the Hundred Year War, Fire Lord Zuko and Avatar Aang transformed the Fire Nation colonies, along with land ceded by the Earth Kingdom, into a fifth independent realm: the United Republic of Nations. Decades later, in 171 AG (After Genocide), the Harmonic Convergence would occur, merging the Spirit World with the material plane. Not only have spirits been reintroduced to the world, forcing them to coexist with a society that has largely forgot about them, but the ability to airbend has been reborn among myriad random individuals throughout the world, bringing the Air Nomads back from the brink of extinction.   This is the second age of the Avatar.