Montresor, Poe's unreliable and hyperbolic narrator, claims that he seeks revenge after Fortunato has added insult to injury.
In the exposition of Poe's Gothic tale, Montresor claims that he has endured "the thousand injuries" that Fortunato has committed against him; however, when his enemy has "ventured upon insult," he states that he can bear no more, and must be avenged. Having decided upon revenge, Montresor commences his intricate plan to approach Fortunato during the Carnival season when Fortunato's disappearance should not soon be noticed. Also, Fortunato, who should be at least somewhat inebriated from celebrating, will be more susceptible to Montresor's luring him into the catacombs on the pretext of tasting the Amontillado.
Montresor's plan is effective as he succeeds in tempting his enemy Fortunato into the damp "vaults." Further, Montresor exploits Fortunato's desire to outdo his rival Luchesi by tasting the Amontillado. Montresor also feigns concern for Fortunato's health because of the dampness of the cavern walls and repeatedly suggests that they turn back. But Fortunato, who will not be outdone later by Luchesi or anyone else, insists that they keep going forward. As Montresor knows, Fortunato is a rapacious man who wishes to taste the Amontillado and judge it before his foe Luchesi has any chance to do so.