Holy shit. HOLY SHIT. This was insane. Easily one of the craziest, most imaginative films, horror or not, I've seen in a long time. Always kept me guessing, and the giant rampage...THAT RAMPAGE. Was very welcome, 'cause I had literally thought, "man, I wish we could see some of those instead of the zombies guys" when the big betting board was shown. Nice sprinkles of tongue-in-cheek too. I think one of the best parts was how you didn't know who to cheer for by the end. The protagonist who you've watched live and fight for their lives, or the antagonist who are doing a dirty deed for the good of the entire world?
Ya' know, this was almost too big for a movie. I could see this as a TV series or mini-series. Different episodes could show us successful rituals, rituals that go only a bit astray, rituals from the others cultures, show us a different monster for each one, and all while hinting and poking towards the whole ancients thing. The finale would be the crew of the movie of course, with all the creatures from previous rituals showing back up for the climatic massacre.