Answer:
The pit, the pendulum with blades and then setting his chamber on fire.
Step-by-step explanation:
Edgar Allen Poe's "The Pit and The Pendulum" tells the story of the narrator who has been left in a dungeon prison. The unnamed protagonist was left in a prison when he first sensed that there was a pit through which his captors had hoped he'd fall. But he tripped on a rope which led him to discover the pit, which he realized was a fall that will eventually kill him even if not instantly. The rats in the pit will eventually kill him, which is a perfect way to torture someone.
Secondly, when he didn't fall into the pit, the captors began to swing a pendulum with a scythe that will slowly pierce and slice through his flesh, a different yet slow form of torture. The psychological pain that he had to go through, imagining the pain that will be his if he ever get hurt, hurts him more.
Lastly, when the two processes didn't work, the Inquisitors put his chamber on fire, hoping that he will be slowly burned to death. But he escaped the fire by luring the rats to bite off the rope that ties him. And then, the psychological torture of being burned to death almost led him to get mad, but he was rescued by the French under General Lasalle.