Prologe
Fire.
Air.
Water.
Earth.
Today, the Four Nations live together in a struggling peace. Though relations between these great kingdoms remains steady, ever since the Avatar, master of all four elements, mysteriously vanished, revolts and looting rampages have plagued the land.
To keep the peace until the next Avatar arrives, a secret warrior group known as The Underground Army was created. For thirteen years they have protected the Four Nations from fearsome warlords, revolts, insane tyrants, and all manner of terrible things; but for now, all is quiet.
The Earth Kingdom, with its newly formed democracy, has been on its toes excitedly looking for the next Avatar who is reincarnated every time he dies and will be born to a different element in a continuously patterned loop. The previous Avatar, Avatar Korra, was born of the Water Tribes, and it is thus that the next Avatar be born of the Earth Kingdom.
However, while this enthusiastic search continues, The Underground Army trains constantly in their cavernous fortresses beneath the soil of the Earth Kingdoms. Any day now the next Avatar could be announced, and they will be ready to welcome him with open arms. Or at least… they were.