Zhang Yimou (Hero, House of Flying Daggers, Curst of the Golden Flower) directs this effects-heavy period fantasy flick. Matt Damon leads a group of mercenaries into ancient China looking for black powder and gets embroiled in a fight involving the Great Wall. Turns out it was built not to keep out Mongols, but hordes of giant monsters. It's not the director's finest hour, but it's pretty as hell and there's an epic amount lot of action. 103 minutes PG-13.