What is the theme of the cask of amontillado?

The main theme of "The Cask of Amontillado" by Edgar Allan Poe is revenge. The story revolves around Montresor's plan to exact revenge on Fortunato for unknown reasons. Montresor lures Fortunato deep into his family catacombs under the pretense of tasting a rare wine called Amontillado, and then walls him up alive as revenge for an unspecified insult.

Other themes in the story include deception and manipulation, as Montresor cunningly leads Fortunato to his demise with false promises and flattery. The theme of madness is also present, as Montresor's obsessive desire for revenge leads him to commit a heinous act without remorse or empathy.

Overall, "The Cask of Amontillado" is a chilling tale that explores the dark depths of human nature and the destructive power of revenge.