In the story of "The Pit and the Pendulum" by Edgar Allan Poe, what does the "descent of the soul into Hades" mean?

This quotation occurs at the end of the first paragraph of the story, and it is a simile comparing that which the author is going through to death. In mythology, Hades is the realm of the dead in the afterlife and does not necessarily have any concept of torment or punishment associated with it. However, in Christian tradition, the term "Hades" is the equivalent of hell, a place of eternal suffering where unbelievers go when they die.

When the narrator speaks of Hades, he says this: "all sensation appeared swallowed up in that mad rushing descent as of the soul into Hades." The word "as" indicates that the expression is a simile. The narrator faints, as the following line makes clear, "I had swooned." Thus the narrator means that the act of losing consciousness felt to him like he imagined it must feel like for the soul of a person to leave this life and descend into Hades or hell. This figurative language is consistent with the descriptions that precede it in the story. In his state of half-consciousness during the inquest, he imagines the seven candles to be angels. He goes on to consider that dying must be very pleasant. Consequently, the use of this simile for fainting is in keeping with the other-worldly and morbid thoughts the narrator is having in his half-dream state.