The Cask of Amontillado was first published in 1846. It is the story of a murder, told by the murderer. Montresor kills his "friend", Fortunato. The story starts out with a foreshadowing of what is to come, with Montresor, confessing his crime to an unknown person. Obviously this person knows him well.
The first sight of irony in the story is that Montresor waits for Fortunato at Carnival. Carnival is celebrated right before Lent starts. This is ironic, because the last day of Carnival is usually described as the last day of sin before Lent begins. Fortunato is already drunk from the party and Montresor lures him away with the promise of tasting a very expensive amontillado. As they are walking down the catacombs, Montresor pretends to act like he cares about Fortunato's ill health. This is ironic in the fact that he is going to kill Fortunato. It is also ironic that they are going down into the catacombs, which are filled with bones hanging from chains, foreshadowing the death that awaits Fortunato. The trowel that Montresor carries and explains away that he has it because he is a Freemason is also ironic, that tool will lead to the murder. The toast that Fortunato makes is also ironic. He toasts "I drink to the buried that repose around us", having no idea that he is soon to be buried there. The beginning of the story is foreshadowing what has already taken place.
One of the best uses of irony is when Montresor confesses to this person.
"It must be understood that neither by word or deed had I given Fortunato cause to doubt my goodwill. I continued, as was my wont, to smile in his face and he did not perceive that my smile now was at the thought of his immolation."
This story makes you, the reader, use your imagination on how this will end. There is no detective investigating the crime. No one knows about it. Montresor even states that for 50 years, no one has disovered what he has been doing. Leading us to believe that he has done this many times before. He never gives a clear motive for killing Fortunato, only to say he had suffered a thousand injuries by him. Just the Fortunato is ironic. Edgar Allan Poe sneaks in clever ironies all through the story. He leaves us wondering who is Montresor confessing to? How long has he been killing? Will he ever be caught?