When they arrive underground, Fortunato asks about Montresor's coat of arms and Montresor, the first-person narrator of the story, tells him it is "A huge human foot d'or, in a field azure; the foot crushes a serpent rampant whose fangs are inbedded in the heel." Fortunato asks: "And the motto?" Montresor replies: "Nemo me impune lacessit," which means "No one injures me with impunity." This may or may not be Montresor's coat of arms and Latin motto. He might be inventing the whole thing for his secret amusement. After all, he has not been telling Fortunato the truth since he encountered him in the street. The cask of Amontillado is undoubtedly a sheer fiction. It is quite possible that Montresor does not have a coat of arms at all. It is possible that Fortunato suspects Montresor's family is of humble origins and is only trying to embarrass him, thinking he might force Montresor to confess that his family doesn't have a coat of arms. The coat of arms that Montresor describes is an extravagant one--a huge golden human foot crushing a snake with its fangs embedded in the heel! This may actually be Montresor's coat of arms, but it seems not only fantastic but too appropriate for the occasion. It almost seems as if Montresor is warning Fortunato--in Latin!--of what is about to happen to him down there in the underground vaults.
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