There are at least five major literary devices in "The Pit and the Pendulum."
Edgar Allan Poe is the "father" of the horror story. The first device is one that he uses so masterfully in his stories:
Suspense. What is known by the narrator as he describes his experience is dark and frightening, and what he does not know further heightens the intensity of the plot development. In the "prison" in which they place him, the dark allows him to feel somethings but other details remain, literally, in the dark as he cannot see.
Another device is imagery. In describing the "lips of the black-robed judges," he describes them as white, "whiter than the sheet upon which I trace these words--and thin even to grotesqueness; thin with the intensity of their expression of firmness..."
Another literary device is the use of metaphors. "My vision fell upon the seven tall candles...seemed white slender angels who would save me...the angel forms became meaningless spectres..."
Foreshadowing occurs with the repeated references to motion and movement: "there came back to my soul motion and sound--the tumultuous motion of the heart...again sound, and motion...and a successful effort to move." This foreshadows the motion of the pendulum. "I saw it in motion..."
Hyperbole (exaggeration): "Could I have broken the fastenings above the elbow, I would have seized and attempted to arrest the pendulum. I might as well have attempted to arrest an avalanche!"
Repetition is used describing first the figures that carried him down into the dungeons: "down--down--still down...," and later describing the relentless movement of the pendulum toward the narrator "Down...Down...Down." And again, "THE PIT...THE PIT."
Poe uses literary devices artfully, not only in his stories, but also in his poetry.