I react in a flash and deliver a blow to Greyback's right forearm, causing him to lose his wand. There's the loud clatter of wood on wood a few feet away. Before I can strike him in the face as well, which I'd really like to do, Greyback yanks us around and rolls over me. I try to shake him off, but the werewolf is at least twice my weight and therefore much stronger. He slams my head on the ground and I see stars.