Final answer:
The use of hyperbole in the opening line 'The thousand injuries of Fortunato...' emphasizes the narrator's grievances and sets up the central conflict of revenge in 'The Cask of Amontillado'.
Step-by-step explanation:
The use of figurative language in the opening line of Edgar Allan Poe's "The Cask of Amontillado" introduces the main conflict through the use of hyperbole. When the narrator states 'The thousand injuries of Fortunato I had borne as I best could, but when he ventured upon insult, I vowed revenge,' the hyperbole emphasizes the extent of the narrator's grievances against Fortunato and sets the stage for the dark themes of revenge and betrayal.
The phrase does not literally mean that Fortunato caused a thousand injuries, nor does it describe physical harm; rather, it exaggerates the wrongs that the narrator has suffered, which have pushed him to seek revenge.