Edgar Allan Poe, the master of the macabre, was gifted in producing a sense of fear, death and looming insanity with the main characters is some of his best short stories, including "The Black Cat," "The Tell-tale Heart," and "The Cask of Amontillado" (which was actually based on a true story that Poe learned about while in the military). These details were highly effective in creating a mood of eeriness.
Imagery is a form of figurative language, where details are provided to create a picture, or "image" in the reader's mind. Poe's stories are particularly effective because of the vivid imagery that he employs.
One bit of imagery that becomes more effective as the story progresses (in the form of foreshadowing) uses sensory details: in this case, auditory details. Onomatopoeia is also present with the word "jingle." Here, the narrator speaks of Fortunato as they move underground, heading (allegedly) for the coveted "amontillado."
The gait of my friend was unsteady, and the bells upon his cap jingled as he strode.
This image becomes even more eerie at the end when the following lines are delivered:
No answer still. I thrust a torch through the remaining aperture and let it fall within. There came forth in return only a jingling of the bells.
In this second image, the narrator draws attention to the mineral deposits that are on the walls around them. Notice the word "web-work," alluding to a spider luring its prey, and the description of Fortunato's eyes that almost seem to describe a zombie, the undead or a monster of the deep:
"The pipe?" said he.
"It is farther on," said I; "but observe the white web-work which gleams from these cavern walls."
He turned toward me, and looked into my eyes with two filmy orbs that distilled the rheum of intoxication.
(Note - rheum: a thin discharge of the mucous membranes, especially during a cold.)
Another image is found several paragraphs later (once again including the bells) as Fortunato is recovering from a coughing fit. The narrator opens a bottle of Medoc (which is a kind of wine). Beside the bells ringing on his cap, note the leer on Fortunato's face, coupled with his toast to the dead around him—more foreshadowing.
"Drink," I said, presenting him the wine.
He raised it to his lips with a leer. He paused and nodded to me familiarly, while his bells jingled.
"I drink," he said, "to the buried that repose around us."
If that is not creepy enough, there is more foreshadowing, and a hidden threat, in the narrator's response:
And I to your long life.
In this instance, the leer of the drunken Fortunato and his reference to the bodies buried in the catacombs around them provides another example as to how effortlessly Poe seems to use few words to create a sense of danger, suspense and impending doom.