In what ways is this story typical of Poe's theory of the brief prose tale? How would you describe the effect or effects of the story?
The chilling effect of the story is produced, in large part, by the dramatic irony throughout. Dramatic irony is when the audience is aware of something that one or more of the characters are not. In "The Cask of Amontillado," Montresor immediately makes it clear to the audience that he is going to seek revenge on Fortunato, and it is going to be terrible; Montresor actually says that he smiles now "at the thought of [Fortunato's] immolation." Immolate, in this context, means to kill or destroy completely. Thus, we do not know exactly what Montresor has planned for his nemesis, but we know it is going to be very bad. Fortunato, obviously, has no idea what is about to happen to him.
Fortunato will continue to be in the dark because, as Montresor divulges, he "must not only punish but punish with impunity." Therefore, Montresor will consider his revenge incomplete unless he is able to make his enemy suffer without incurring any consequences for himself. Further, the original offense "is equally unredressed when the avenger fails to make himself known to him who has done the wrong." Thus, Montresor longs to destroy Fortunato, and he has to make sure that Fortunato knows that he is responsible.
As Montresor leads Fortunato deeper and deeper into his family's catacombs, plying him with more and more with drink, we begin to understand that he means to leave Fortunato there, especially when he pulls a mason's trowel out of his cloak—why would he be carrying such a tool with him unless he meant to build a wall?! Fortunato, however, remains blissfully unaware of the impending danger. As he is led closer and closer to his doom, our tension increases, the effect of the story's dramatic irony.
Poe defined the prose tale as a story that a reader could finish in a single sitting.
The effect of the story is to establish an atmosphere of rising suspense and fear. Montresor is determined to take revenge on Fortunato for offenses that he does not tell us about, but have harmed him in a permanent way. He vows revenge.
The effect that Poe creates is that of a story of deception where Montresor plays upon Fortunato's ego to lure him down into the catacombs and subsequently to his death.
Montresor is very calm and measured as he leads Fortunato down into the damp, creepy, skeleton filled space. He even suggests that Fortunato's health will be damaged by the damp air in the catacombs. But, Fortunato is so vain, that he insists on tasting this exquisite wine that he is promised.
The ultimate effect is horror that takes the reader by surprise. When we realize that Montresor intends to wall Fortunato into his own tomb, to bury him alive, the reader feels a cold chill. Montresor is so faithful to his task, walling up Fortunato.
It totally creeps out the reader to realize that Montresor, an ordinary individual, is capable of such abject cruelty and indifference to the cries of his victim. He is a cold, cruel, killer, one that we did not see coming. This type of killer is much scarier than the straight in your face slasher murderer.