Stronger together, weaker without ( a Voltron au)

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 Katara and her brother, Sokka, discovered the new Avatar, an Airbender named Aang. He was the only one that could save the world. He ended the war a year later, therefore restoring peace to the three remaining nations. After ending the war, Aang and his friends, Katara, Sokka, Toph, Zuko, Suki, and Mai, went to reside in their old home in Ba Sing Se. Years passed and the cycle of Avatars continued with a waterbender named Korra. She and her friends balanced the spirit world and the physical world. Soon, the circle once again continued.

Now a new threat threatens the nations, and the Avatar needs to be found.