Montresor wants to gain Fortunato's trust so that he can lure him into the catacombs and exact his revenge for the perceived insult he believes Fortunato has committed against him. By pretending to be a concerned friend, Montresor is able to manipulate Fortunato into following him to his demise.
Fortunato's crime against Montresor is not explicitly stated in Edgar Allan Poe's "The Cask of Amontillado." However, it is suggested that Fortunato may have insulted or wronged Montresor in some way, prompting Montresor's desire for revenge.
It is ironic because Montresor is actually planning to kill Fortunato. By toasting to Fortunato’s long life, Montresor is being hypocritical or insincere since he intends to end Fortunato’s life.
Montresor's response to Fortunato's screams adds to the mood of the story by showing that Montresor feels some guilt and compassion for what he is doing. This mood quickly passes and he goes back to being filled with hatred.
This shared interest in wine foreshadows that Montresor might use this to lure Fortunato to come with him to get the Amontillado, so his plan to kill him can succeed.
Montresor drinks to show casualness and to keep up appearances while leading Fortunato into his trap. It helps him maintain his façade of friendship and trust until he can exact his revenge. Drinking also allows him to maintain a sense of control and cunning over Fortunato.
The nature of Fortunato's insult is not explained in detail in Edgar Allan Poe's "The Cask of Amontillado" because the story is a first-person narrative told by Montresor, and he chooses not to disclose the specific insult. This lack of detail adds to the story's ambiguity and creates a sense of mystery and intrigue.
He was thinking about Fortunato's death. Mostly because he wants revenge and wants to kill him
Fortunato seems not to trust Montresor and asks whether he is one of the masons.
The main conflict is that fortunato had done something to montresor and now montresor wants to get back at him by killing him.
They don't have a conversation about "brotherhood" per se. The conversation is about the brotherhood of the Freemasons. Fortunato makes some strange gestures that perplex Montresor. Fortunato states that is because Montresor is not of the Brotherhood of masons, meaning the Brotherhood of the secret group the Freemasons. Montresor says that he is and Fortunatos says it is impossible and asks for the sign. Here Montresor produces a trowel to prove he is a mason. This gets a laugh out of Fortunato, because it is a play on the word 'mason'. Fortunato means it in the Freemason sense, while Montresor means it in the bricklayer sense. A very nice pun. A very ironic pun considering that Montresor is about to use the trowel as a mason would to build a brick wall to seal Fortunato in the cellar till his death.
Montresor wants Fortunato to drink the Medoc wine to keep him warm and toasting to the success of their endeavor. It helps to loosen Fortunato's inhibitions and lead him deeper into Montresor's trap.
In "The Cask of Amontillado," the main character Montresor seeks revenge against Fortunato for an insult. Montresor manipulates Fortunato's pride and ultimately leads him to his death in the catacombs. The conflict between the two characters is driven by Montresor's deception and betrayal of Fortunato's trust.