Complex sentence: They hypnotized him and manipulated his psyche to prevent him from dreaming; this kept him from using the Materioptikon for criminal purposes but caused him to lose his mind and shrivel to a skeletal wreck of a man.
Split into simpler sentences: They hypnotized him and manipulated his psyche to prevent him from dreaming. This kept him from using the Materioptikon for criminal purposes but caused him to lose his mind and shrivel to a skeletal wreck of a man.