Okay, holy shit, now I get it.

See, seeing Alternia in a spiral galaxy just like ours had me thinking that that might not be Earth. 

WHICH WAS OBVIOUSLY STUPID IN RETROSPECT.

Because there is a planet, surrounded by the very constellations that surround Earth. Constellations that correspond to each of our 12 trolls. They created a universe, and were going to (I know this because I read ahead) rule over the Earth. Woah.