The anti-christ Wan (avatar) had stolen the elemental powers of the spirits which he used to disrupt the balance between evil and good and furthermore instigated rebellion into the frail hearts of man which led to war against the spirits. In his conquest he'd also merged with Raavu and become the light-bringer, Lucifer.
Unalaq will descend upon mankind during the harmonic convergence and defeat the anti-christ, for he is not only man but also Vaatu; half-man, half-god. Thus the anti-christ will be defeated and Vaatu will reign over this world and from his reign light will once against spring and the balance between good and evil will once again be restored.

Amen