In "The Cask of Amontillado", is it ironic that for Montresor to enjoy his own life, he has to take Fortunato’s?
(By the way, the story is called "The Cask of Amontillado." A cask is like a small barrel that contains liquid; in this case, Montresor says there is cask of very exotic and expensive wine--amontillado--that he wants Fortunato to taste; this is a trick to lure Fortunato into the tunnels beneath his palazzo/house in order to kill him.)
There is certainly irony in the sense that Montresor must kill Fortunato in order to feel as if he has been avenged for his perceived insult at the hands of Fortunato, and therefore feel happy and at ease about his own life.
Montresor is enough of a sociopath that he sees absolutely nothing wrong with having taken Fortunato's life. He toys with the man, who is already befuddled with wine, like a cat toying with a mouse before it kills the mouse.
The fact that he takes such pleasure in punishing Fortunato for an insult he never even identifies to the reader makes the story that much more macabre. And because he is a sociopath, he feels none of the remorse that the main character feels in "The Telltale Heart," also written by Poe. In fact, it is with great satisfaction that Montresor seals the last brick in place of what becomes Fortunato's tomb, and though the reader is repelled by what he has done, Montresor doesn't blink an eye. The problem has been solved and he is happy.
(It is also ironic that "Fortunato" sounds like "fortunate," and Fortunato is anything but fortunate. You might also want to note that this story is based upon a true story that Poe heard while he was in military service. That just makes the story a little creepier!)