This is located in the Catacombs. Because the Dahaka is chasing you, consider using slow time to escape him. Get to the section where you have to pull three stones out of the wall to raise the central area. After pulling the first, go to the stairway, make a right, run on two walls and jump to the bar on the right side. Swing from the bar and follow the path and make a quick left. The fist is in a weapon rack to the left. The Rayman fist is unbreakable with a high attack rate but does little damage. If you throw it, you lose it forever.