What is the tone and mood of this text?

Mood refers to the emotional atmosphere of the text, or the feeling the text attempts to inspire within the reader. The mood of this particular story is rather dark and tense as a result of the dramatic irony. We know that Montresor is plotting Fortunato's "immolation," but Fortunato does not, and this knowledge makes the story feel very tense for readers. We are always waiting for what seems to be inevitable: Fortunato's horrible death.
Tone refers to the author's attitude about the text's subject. This story's tone could be described as ironic. One of Montresor's requirements for revenge is that "[he] must not only punish, but punish with impunity." It is imperative to him that he never experience any negative consequences of this murder. However, in the final paragraph he tells us that when Fortunato is finally locked away within the wall of his family vault Fortunato stops responding to Montresor, and Montresor's "heart grew sick . . . [and he] hastened to make an end of [his] labor." He attributes this feeling of sickness to the dampness underground, but that hasn't bothered him until now. One might interpret this feeling of sickness to be the effect of guilt. Further, the fact that he is confessing to this murder some "half of a century" after he commits it also makes it seem as though he feels guilty. Poe seems to realize this, though Montresor does not.