Both The Black Cat and The Cask offer a glimpse into the characterization of someone going mad or becoming completely evil due to revenge or obession (or both). In the Black Cat the narrator hates the black cat because it loves him. When supposedly the cat returns from the grave in the guise of a new black cat, he determines to kill it too. This obsession becomes the catalyst, the driving force, that motivates the character. Likewise, this is the same with The Cask of Amontillado in that Montressor has long planned his revenge on a wine critic whose grandiose claims insulted Montressor.
