100 Years after the Death of Avatar Aang, the new Avatar is a Waterbender. Peace has returned to the world, and all is well. The large threat of the Fire Nation had been eradicated many years ago, and every last known Energybender has died.
At least, that's what people think.
However, when the legendary battle was going on, there was another Energybender... This Energybender, Kain, saw the fall of the Firenation as a perfect opportunity to take over the world.
And so, the Energybending began his plot. He captured Fire Lord Ozai, and broke Fire Princess Azula out of the Asylum. Then, he told them of his plot for world domination. However, not even these two know his real intentions. Kain used his Energybending to keep Ozai and Azula at their current age for 100 years.
Meanwhile, deep in the legendary Lion-Turtle's homeland, the giant creature sensed what was going on, and using the last of his power, he did to Toph Be Fing what Kain had done to Ozai and Azula: Granted her eternal youth. The Lion-Turtle's goal: To keep Toph alive so that she could lead the legion that would stop these two power hungry Firebenders and their master.
And now it is time to choose. Will you help Toph stop Kain, Ozai, and Azula, or will you help Kain with his evil plot for world domination? It's all up to you, my friend.