When thinking of titans I think of large godlike/demonlike entities, maybe that's the problem. I don't mind the Sky part, but Titans sounds large in shape.

I also dislike the use of portals. Don't get me wrong, I love portals and I really like how you implemented it, but from a developers kind of view it looks so much like copying portal. And as long as you can't see through them you might as well make them teleporters or something.

Other than that, great effort, and as I said on facebook: Ender's game for the win!