The surrounding of the man in the story help you understand the mood in the story and his reaction to various levels help you understand more.
Step-by-step explanation:
The main theme and the idea of the story pit and the pendulum is that the death sentence seems better to the narrator compared to the torturous fear that the narrator has to bear and is made to bear. He has completely lost hope, will.
The mood of the Pit and the pendulum is full of terror. It has an urgent mode in it. The mood is fearful, dark and terrified.