The author specifically chose the setting of the crypt in “The Cask of Amontillado” to go with an ironic, spooky and sophisticated tone to create an ominous and disturbing mood.

Setting is the time and place of the action of the story.  The story is set in Montresor’s family crypt, where wine is stored.  Crypts have plenty of bones and are dark and ominous.  The fact that the story takes place during carnival, which is important because it leads to the irony because you don’t expect a murder during a time of merriment.

Tone is the author’s attitude toward a subject.  The tone of this story can be described as ironic, spooky and sophisticated.  Consider the author’s word choice in the first line.  You can hear the sophistication, but there is definitely a spookiness to it.

THE THOUSAND INJURIES of Fortunato I had borne as I best could, but when he ventured upon insult I vowed revenge.

There is also a lot of irony in the tone.  The tone is ironic because the irony is clear from the word choice.  For example, Fortunado toasting the dead and Montresor resting in peace are backed up with the overall feeling from the author’s word choice that we know something that the characters don’t, and there are contradictions everywhere.

Consider also how the setting and word choice create the mood, or the reader’s feelings when reading the passage.

I passed down a long and winding staircase, requesting him to be cautious as he followed. We came at length to the foot of the descent, and stood together upon the damp ground of the catacombs of the Montresors.

The choice if words like “winding,” “cautious,” “descent,” “damp,” and “catacombs” were carefully chosen to create the ominous and disturbing mood.