What is a persona of the narrator in The Cask of Amontillado?

The narrator (Montresor) is unreliable and quite possibly mad. His obsessive hatred for Fortunato is claimed to be from a succession of offenses accumulating and then topped off with an unforgivable and unspecified insult which quite possibly do not exist. He bait his victim by his pride and seals him up still alive in the walls of the catacombs of some unspecifed Italian city.