Montresor is a complex and intriguing character whose desire for revenge drives the story. Given that his family motto is Nemo me impune lacessit, which means "no one insults me with impunity," Poe seems to suggest that this drive is one that defines his existence. His noble lineage seems to be at least part of what makes him murderous. He says he has cause for seeking revenge—that Fortunato has insulted and injured him—but he never gives any specifics. The cause of his injured pride, then, is unknown and may be imaginary. Montresor shows his skill at deception by how he tricks Fortunato, and his skill at planning how he sets up the final resting spot in the catacomb and guides Fortunato to it. While there is one moment that seems to give him pause (when Fortunato screams), he is ultimately cold, calculating, and relentless.
Fortunato first appears in the story through Montresor's discussion of how Fortunato has hurt him. When he appears in the story in person, he's wearing a costume—specifically, motley—clothes a jester or fool would wear. These two factors largely frame Fortunato's role throughout the story. Readers experience Fortunato through Montresor's narrative, which is clearly biased and likely insane—and Fortunato himself plays the fool at many turns, missing clues and making choices that make his fate worse. Fortunato's ego, greed, and competitiveness cloud his judgment. Montresor tells readers Fortunato thinks he is an expert on wine but he certainly doesn't act like it. He acts like an enthusiast but also like the opposite of an expert: he guzzles wine in quantity, with no care or respect. (This may be part of what offends Montresor.) Montresor notes that he regularly overindulges in such a way. Throughout the story—until the very end—Fortunato seems to think he and Montresor are friends and that their fondness for wine creates a connection between them. It isn't until Montresor locks him in a crypt and begins to brick him in that Fortunato finally realizes he's been tricked.
Luchesi is another wine expert. He does not appear in the story in person, but Montresor repeatedly mentions him to Fortunato. Montresor pretends he is on his way to see Luchesi to ask about the value of the Amontillado he supposedly has found, but really he is just using Luchesi as a foil to goad Fortunato into descending into his vaults.
Montresor's servants do not appear in this story in person. Judging by Montresor's references to them he does not have a high opinion of their work ethic or honesty. He says he explicitly ordered them not to leave the house, fully expecting they would leave as soon as his back was turned to join in the carnival festivities.