Revealing mistake: In the raid scene where we first meet Malagant, a four-sided wooden tower is shown on fire, and then it collapses from the damage. However, the tower's front legs don't buckle and as it falls, the burning tower appears to be completely intact -- it has simply been pulled down by ropes that are partially visible from the front.
Continuity mistake: In the scene at the end when King Arthur's funeral raft is floating away, you see white smoke coming from the wood at the foot of the raft. Cut to the shore, and the flaming arrow is lit and shot. Cut to the raft, and the flaming arrow hits the now smokeless raft in the spot where the smoke was. Cut to the shore, then back to the raft, where the fire begins to grow on both sides of the raft, nowhere near the now smokeless and flame-less spot where the flaming arrow hit in the previous shot.