The single effect of this story and many of Poe's stories is blatant, mind-numbing fear. In "The Pit and the Pendulum" specifically, the narrator's fear begins with the Inquisition, being found guilty, and thrown into this hellish prison. He is kept in the dark, passes out only to wake and find someone has left food and drink, then immersed in complete darkness (the fear of the unknown is horrible in itself). Blindly, he "explores" his surroundings only to stumble and fall. Upon falling, he discovers had he not fallen, he would have walked into a seemingly bottomless pit, most certainly to his death. Upon next waking, he finds he is tethered to a table where a pendulum is swinging closer and closer to slicing him in two. Faced with certain death, this time illuminated with many bright lights, he is forced to think quickly and rub meat left for him to eat on the ropes holding him. Rats chew through these ropes (having rats running all over you is enough fear for some) and the narrator again escapes death, but just barely.
With all the experiences the narrator suffers, it is truly emotional, mental, spiritual, and physical horror.
i think the single effect in *the pit and pendulum is the rescue of the narrator which means the servival of free thinking .the effect that Edgar allan poe is building from the beging of the story to acheive ,and that why edgar allan poe said that the story should be read in one sitting.
This, like all of Poe's writings, conveys a feeling of fear, depression, and hopelessness. Though it is different than some of his other stories by the fact that it has an ending full of hope and relief.