Well that plot took it's sweet time kicking in. Honestly, I was starting to wonder if this show had totally lost focus.
Part of me hopes that Korra's irrational behaviour of late will turn out to be the result of some kind of resonance with Vaatu. Maybe he and Raava are still somewhat connected and the Avatar spirit can sense when his influence is growing. I really hope it's not just poor writing.
Hey, I just realized -- Wan gained his elements in the same order as the Avatar cycle. After fire comes air, then water, then earth. That must be why the cycle goes in that order.
It's also the order in which Rokku, Aang and Korra mastered them. I wonder if it's just a tradition or something more fundamental to the way an Avatar works. Meaning, is it even possible for an avatar to learn them out of sequence? Could easily be just a coincidence, but Aang did try using fire before he'd mastered either water or earth and was unable to control it.
Or at least, could we see a "dark avatar" if someone merges with Vaatu?
I have a feeling that this is what is going to happen with Unalaaq during the Harmonic Convergence.
Here's a scary thought; maybe that's exactly what need to happen to restore balance? Maybe from here on out there will be two Avatars acting as yin and yang? I think it's either that or Vaatu and Raava will be reunited, ending the line of Avatars forever....OR they will both become merged with the Avatar spirit?
However it plays out, I'd be a little disappointed if all they end of doing is shoving him back in his cage for another ten millennia.