Edgar Allan Poe, the author behind the eerily vengeful short story, "The Cask of Amontillado," uses carefully constructed irony to solidify the intended deeper meaning to his somewhat twisted tale. Instead of having the character simply lure his victim threw his plan he has the character basically taunt the poor character of Fortunato. Be it something the character says or an action he commits irony is a big part of this story, almost as big a part as the theme of revenge. To start off, while Montresor is dragging Fortunato down to the vaults through the catacombs he takes notice that Fortunato is not in good health and he repeatedly says to Fortunado, "are you sure you want to continue your health is precious" which is a show of dramatic irony because we know that Montresor is taking Fortunato down there to kill him. Also, this is verbal irony because even though Montresor hates Fortunato he is showing a facade that he cares and it is a bit of a dare to Fortunado saying that Montresor can go back and get someone else to do what he was asked to do. Along with that when Montresor and Fortunato take a break and grab some wine that was already there in the catacombs and they both toast to Fortunato's long life. This is another case of verbal irony because Montresor is toasting to his long life while carrying out a plot to kill him. The plot to kill Fortunato brings the next point of irony into range.
In addition, while the two are walking Fortunato stops and makes a grotesque notion and asks if Montresor is in line with The Masons, to which Montresor replies by showing him a trowel. This is a case of dramatic irony because later down the line of events in the story Montresor eventually kills Fortunado with the trowel. Not directly though, Montresor uses the trowel to brick up Fortunato while he is chained against the wall. So, in the scene in which Montresor shows Fortunado the trowel Montresor is probably thinking, "oklook at the trowel I'm going to kill you with it later, but for now pay no mind to it.