In a world inhabited by humans, fantastical, hybrid animals, and spirits, there is a constant struggle for balance; balance within oneself and balance between the four nations. Each nation takes its native element for its name, and within each nation there exist certain people with the ability to “bend” or manipulate one of those elements: Water. Earth. Fire. Air. Only one person possesses the powerful ability to bend all four elements. That person is the Avatar, a reincarnated being who is charged with maintaining balance in the world. With each lifetime, they are reborn into the next nation in the cycle, for the benefit of all humanity.