How would you describe the persona that Poe has created for Montresor? Why might Poe have chosen someone like Montresor to tell his story?

Poe wanted to write a perfect-crime story in which the perpetrator was never caught and punished. A contemporary story in which a murderer does not get caught--as the murderers do get caught, for example, in Poe's "The Black Cat" and "The Tell-Tale Heart"--would have been impossible to publish in his day because of certain unwritten literary conventions. Editors would have regarded such a story as a incitement to commit murder and a blueprint for how to do it without being punished. But Poe felt that a story about a perfect murder committed long ago and far away would pass censorship and not be too shocking for the reading public. His story "The Cask of Amontillado" was actually first published in a ladies' magazine. Montresor killed Fortunato at last fifty years earlier and in distant Italy. Montresor himself was probably dead by the time the manuscript came into the hands of Poe and he translated it into English. So Montresor had committed the perfect crime.

I am assuming that Montresor is not speaking to someone but that he wrote his story in his own language--either Italian or French--and sent it to a confidant or confidante by mail and that it was found among that person's papers after his or her death. Or possibly Montresor wrote such a letter but decided not to send it after all, so it was found among his own papers after his death. The style of the writing does not sound like someone speaking but like someone writing.

Since the crime was committed in Italy, Poe needed a first-person narrator who was living in that country. Poe could not write the story in the third-person because Montresor was the only person in the whole world who knew he had killed Fortunato, how he did it, and where he hid the body. Montresor comes across as a very angry, vindictive, cunning, and patient man. His name is French, which suggests that he is a relative newcomer to Italy and a permanent outsider to the best society. He sounds exactly like someone who would commit such a horrible crime. That shows the great genius of Edgar Allan Poe. Since Montresor is addressing someone whom he calls "You, who so well know the nature of my soul," he can leave out a lot of exposition and focus on the dramatic elements of the tale. This leaves many readers wondering about a lot of things. Some people even question whether Montresor really suffered the injuries and insult he claims motivated him to dispose of Fortunato as he did. Some readers think he must be insane--but it seems doubtful that an insane man could plan a perfect crime so meticulously and explain it so thoroughly to a third party. 

Montresor is a character who, like most characters in fiction, was hand-crafted to fit the role the author wanted him to play. He reveals in his dialogue that he was once a wealthy and socially prominent man but has fallen on hard times. This makes him hypersensitive--and it would seem that the "injuries" he speaks of included many cruel jibes from the wealthy and comfortable Fortunato. Montresor says to him:

“Come,” I said, with decision, “we will go back; your health is precious. You are rich, respected, admired, beloved; you are happy, as once I was. You are a man to be missed. For me it is no matter." 

The fact that Montresor lives in a palazzo is not impressive. The palazzi of Venice were decaying and could be rented cheaply. All those bones in the catacombs are undoubtedly not the bones of Montresor's ancestors. They probably came with the palazzo and he had to put up with them because there was no place to move them to--and anyway, the landlord would never permit a tenant to dispose of all his ancestors' bones. Montresor is well educated and refined, but he is a poor man who lives from hand to mouth. He did not buy that "pipe" of Amontillado for personal consumption. A "pipe" of wine contains 125 gallons. He bought it because it was, as he said, a "bargain" and he could make some money by bottling and selling it by the case. The money would be important to him. If he paid, let us say, the equivalent of ten dollars a gallon and sold it for the equivalent of twenty dollars a gallon, he could make around the equivalent of twelve hundred dollars, which no doubt he badly needs. In those days he could live for a year or two on that much money. He has lazy and indifferent servants because he either pays them little or nothing at all.

Poe himself was adopted by a wealthy man and then subsequently disowned by him. Poe had to scratch out a living for himself his child-wife and her mother. He is secretly writing about himself in "The Cask of Amontillado." He made plenty of enemies as an often vitriolic literary critic, and "Fortunato" is probably a substitute for someone Poe would really like to kill. The story is like a dream. In dreams we often take real emotions and disguise them so completely that we ourselves cannot understand their real meaning. One of the functions of dreams is apparently to relieve ourselves of painful emotions through fantasy. When Montresor leaves Fortunato to die a horrible death chained to the rock wall, Montresor achieves "closure," and no doubt Poe obtained some degree of closure for himself by writing his story in the persona of Montresor.