Water. Earth. Fire. Air. My grandmother used to tell me stories about the old days, a time of peace when the Avatar kept balance between the Water Tribes, Earth Kingdom, Fire Nation, and Air Nomads. But that all changed when the Fire Nation redistributed their land. Only the Avatar mastered all four elements. Only he could stop the ruthless firebenders from their dystopian program of social progress and the abolition of class. But when we needed him, he disappeared.

And then idk the show is about the other three nations invading the Fire Nation in order to do a Bourbon Restoration.