What is the mood or atmosphere of this story?

The overall mood and atmosphere of Poe's classic short story "The Cask of Amontillado" can be described as disturbing and menacing. At the beginning of the story, the narrator explains to the reader how he got revenge on Fortunato for causing him a "thousand injuries." Montresor proceeds to outline his requirements for committing the perfect crime and elaborates on how he deceived Fortunato into following him down into his family's catacombs. By utilizing dramatic irony, Poe creates an eerie, ominous mood. The reader is aware that Montresor has an evil plan for the unsuspecting Fortunato, who is visibly intoxicated and unaware that he is being deceived by a malevolent enemy. The carnival setting also adds an element of chaos and bizarre to the story's atmosphere, which heightens the suspense and contributes to the unsettling mood. As Fortunato follows Montresor into his family's vaults, the mood becomes increasingly ominous and threatening. The dingy nature of the catacombs and the skeletons surrounding the two characters also contribute to the sinister atmosphere. Once Montresor successfully clasps Fortunato to the back wall of the vaults, Poe creates an atmosphere of danger, panic, and fear as Montresor steadily builds a wall to bury his enemy alive.

The mood of this story is characterized by foreboding and danger. We know from the outset that Montresor is planning to do something terrible to Fortunato. He says, "I would be avenged" and that "I must not only punish but punish with impunity." Therefore, we know Montresor is plotting revenge for the "thousand injuries" Fortunato has done him as well as whatever "insult" Fortunato has offered him. Further, Montresor vows that he must not only exact such revenge, but he must do so without incurring personal consequence for himself. He feels both that he must go unpunished for whatever retribution he exacts as well as that he must make himself known as the author of this retribution. Several times Montresor hints about what he plans to do; the foreshadowing of his later actions lends to the foreboding atmosphere. His calculated coldness—his ability to deceive his victim up until the last moment—helps to create a mood of danger.