Complex sentence: Sneering, Castor gleefully informs Archer that every time he looks at the mirror, he will see him, and begins to mutilate his face with a jagged piece of shrapnel.Archer finally kills the madman by ramming the harpoon through his body, pinning him to the wall.
Split into simpler sentences: Sneering, Castor gleefully informs Archer that when every time he looks at the mirror, he will see him. The obviously insane Troy then begins to actually mutilate his face with a jagged piece of shrapnel until Archer finally kills the madman by ramming the harpoon through his body, pinning him to the wall.