Luchesi isn’t really a character. He’s more of a plot device. He helps drive the action. Luchesi is Fortunato’s rival in wine tasting. Montresor doesn’t really need to bring up Luchesi to lure Fortunato to his dire fate. The prospect of Amontillado is enough. Luchesi is a kind of insurance for Montresor. He brings Luchesi up whenever he wants to keep Fortunato distracted – like right before he “fetter[s] him to the granite.” But again, Montresor doesn’t really need to evoke the name of Luchesi. Fortunato is not only drunk, but also willing to do anything to get to the Amontillado. Montresor is just playing with him, exploiting Fortunato’s “weak point[s],” with a little help from Luchesi.