Ages before this Harmonic Convergence, Vaatu broke through the divide that separates the physical and spiritual worlds, allowing spirits to roam it freely. Having won their previous duel, Raava kept Vaatu in check for almost ten thousand years, until Vaatu manipulated Wan into using firebending to free him from Raava's grip. When Wan realized the gravity of his mistake and after seeing the effects Vaatu had on peaceful spirits, he set out on a journey to receive all four bending arts from the lion turtles in order to help stop Vaatu. However, since no human had ever carried more than one element before, the air lion turtle decided that Raava must carry the element for him until he had mastered them, thus pairing them up. Together, they trained to master the four bending arts for nearly a y