Ok, so I watched the Avatar origin episodes...
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I thought it was going to be a letdown, but it was alright. Not great, but I mostly liked everything about it. Except for the dark spirit part. It reminded me of Samurai Jack.
Long ago in a distant land, I, Vaatu, the shape-shifting Master of Darkness, unleashed an unspeakable evil! But a foolish human warrior who mastered the four elements stepped forth to oppose me. Before the final blow was struck, I tore open a portal in time and flung him into the future, where my evil is law! Now the fool seeks to return to the past, and undo the future that is Avatar: The Legend Of Korra!
Spread out all around us is a petrified world, a world of Things, where we ourselves, our gestures, and even our feelings figure in as Things. Nothing can belong to us as truly our own in such a landscape of death. Under commodity occupation the most concrete truth about everything is the truth of it's infinite replaceablity.