Poe's story is somewhat like Dante's Inferno. The setting is of the utmost importance because of the effect it has on the reader's imagination and on the reader's nerves. In following Montresor and Fortunato down into the catacombs and along the dark, winding tunnels lined with human bones, the reader is being taken on a trip through a place that resembles hell. This was Poe's intention. Montresor lures Fortunato underground, and Poe lures the reader underground. By describing the actual horror of the setting, Poe makes the reader experience the horror that must have been felt by Fortunato when he found himself trapped down there and realized that he was going to be left to die there. Just as Fortunato is lured by the Amontillado, the reader is lured by the nonexistent cask of wine. The reader wants to see that cask and to taste that exquisite wine in imagination. An interesting question would be: When does it become apparent to Fortunato and to the reader that there never was any cask of Amontillado?
The word impact means bearing or involvement in the case of the this story. It is asking how strong is the setting in realtion to the story?
The setting is very important. It begins on the street at a time when Christians are partying because it is almost time for the season of Lent. Lent in the Catholic tradition is a very serious, somber time when people sacrifice food and wine for their religious pennance.
The story would not work if it hadn't taken place during what is called "Carnevale" in Europe. That is where the word carnival in English got its roots. Carne = meat. It is a time when people party and eat meat and drink wine because they will give all that up during Lent. It is also a time to dress in costumes. Neither Fortunato nor Montresor can be recognized because they are wearing disguises. A perfect way to set someone up to be murdered. Just think Mardi Gras in the United States!
Impact means how does it affect you as you read the story. "The Cask of Amontillado’’ is one of those stories that relies heavily on the setting to create the sense of forboding and danger that is present from the very beginning. Although the setting in terms of time and exact location are vague, the hints of being in the catacombs of Montresor's home and being aware of his evil intentions causes increased tension on the part of the reader. The murky atmosphere of the catacombs creates fear and anxiety in the reader that increases as his evil plans of revenge become more and more obvious as the story progresses.
In this sense 'impact' means what effect or impression does the setting give the reader.
Poe's writing is considered to be in the Gothic genre, therefore his setting is similarly Gothic. The two men go deep down into the dungeon or cellar and all the words used to describe the setting give the reader a creepy feeling. The fact that they are in a crypt is scary enough but Poe continues to 'scare' the reader by describing in detail the thick stones, the dampness of the room and so on.
In this way the 'impact' on the story and the reader is very strong. The story would not be as strong if it were set in a living room. He could have just as easily chained Fortunato up in a bedroom hidden away, but he did not. He brought him into a tomb alive, which makes the story much scarier.