Complex sentence: In the Labyrinth, the Sartan who should have been monitoring the prison realm either died or left, and the Labyrinth slowly evolved from a temporary correctional facility into a sadistic and sentient prison.
Split into simpler sentences: In the Labyrinth, the Sartan who should have been monitoring the prison realm either died or left. And without its caretakers, the Labyrinth slowly evolved from a temporary correctional facility into a sadistic and sentient prison.