Montresor symbolizes the madness of the carnival, because just like him the carnival was full of madness and craziness
Montresor knows that Fortunado will be dead very soon.
Montresor starts coughing and has to catch his breath. Montresor offered to turn back but Fortunato refused, and mentioned how the cough will not kill him. The comment foreshadows that something more sinister is about to happen to Fortunato, even though he is completely unaware.
Poe's overall tone in The Cask of Amontillado is unsettling and ominous.
Fortunado's costume reflects his personality, because it is crazy and wicked.
Poe shows a dark and suspenseful mood throughout the story.