Note that we’ve only gone a few hundred words into the story, but I’ve written a few thousand looking at its technique. You may quibble here and there, but I hope I’ve impressed you with how much is going on here.
General: Confident of his game with Fortunato, Montresor puts on an act, toying with the reader by proxy. The devices introduced early on in the story are re-employed, with a few special flourishes.
The alliteration of “white web-work which gleams from these cavern walls” makes that line a declamation, hammy and theatrical. This is no accident. Nor is the “web” imagery. The spider plays with the fly.
The “filmy orbs distilling the rheum of intoxication” are a mirror trick, compounding the web imagery. These webs are presumably within Fortunato, but we can’t help but see the nitre reflected in them. Montresor has Fortunato in his webby lair and intoxicated, in similar condition to a spider’s prey. And though Poe doesn’t say as much, the context and imagery point strongly to Fortunato being under Monstresor’s spell. It only requires a nudge to communicate the idea without coming right out and saying it, and Poe gives us that nudge. “How long have you had that cough?” Montresor asks, and only after he asks does Fortunato start coughing, as if the suggestion triggered it through some hypnotist’s trick.
After the lengthy cough, Montresor tests his influence and offers to take Montresor back to the carnival, though he lets his resentment show: “…you are happy as once I was” is obviously petulant. “You are a man to be missed. For me it is no matter. We will go back; you will be ill, and I cannot be responsible.” He makes a concession to Fortunato’s pride, building it up, only to use it against him with the interrupted line: “Besides,” he says, “there is Luchesi–” That Fortunato interrupts him reveals how thoroughly he’s played Fortunato: Montresor has set the score, and Fortunato doesn’t miss a beat.
Next, Montresor serves him wine, advertantly to ward off the chill, but of course the the added effect of further impairing Fortunato’s judgment. He draws out a bottle from a row of its “fellows lying on the mould” and knocks off its “neck.” He is compounding the imagery of a predator in its lair: these are not “bottles”; they are “fellows,” and they drink one from its shattered neck, vampire- or spiderlike.
The following lines are pointed ironies and foreshadowing. Fortunato drinks to the dead around them; Montresor to his “long life.” The vaults are extensive, and therefore ominous. The Montresors were great and numerous, implying that they no longer are. They have become unfortunate. Fortunato has forgotten Montresor’s family arms, which is telling for two reasons. Those who forget history are doomed to repeat it, and the arms contain a dire warning: “No one attacks me with impunity.” To which Fortunato replies fatuously: “Good.”
Playing with the reader by proxy — this is a consequence of any tale of suspense, but there’s more than just dramatic irony here; there’s the question of what is going on, and therefore Poe has more scope to play with our emotions: with foreboding, misgiving, apprehension, and even hope.
Mirror trick: without saying that this is a spider’s lair, Poe compounds the imagery to slip that suggestion into the backdoor of your mind. The rheumy eyes do no literally reflect the nitre on the walls, but they sure do reflect it figuratively, and the bottles personified as fellows help sustain the metaphor and conjure the space.
Implicit metaphor: Poe manages implicit metaphors so carefully, so consistently, that you register first on an emotional rather than intellectual level. A direct, clear metaphor is better than an unfocused one, but what Poe manages here seems much more powerful still.
"The pipe," said he.
"It is farther on," said I; "but observe the white web-work which gleams from these cavern walls."
He turned towards me, and looked into my eyes with two filmy orbs that distilled the rheum of intoxication.
"Nitre?" he asked, at length.
"Nitre," I replied. "How long have you had that cough?"
"Ugh! ugh! ugh!—ugh! ugh! ugh!—ugh! ugh! ugh!—ugh! ugh! ugh!—ugh! ugh! ugh!"
My poor friend found it impossible to reply for many minutes.
"It is nothing," he said, at last.
"Come," I said, with decision, "we will go back; your health is precious. You are rich, respected, admired, beloved; you are happy, as once I was. You are a man to be missed. For me it is no matter. We will go back; you will be ill, and I cannot be responsible. Besides, there is Luchesi—"
"Enough," he said; "the cough is a mere nothing; it will not kill me. I shall not die of a cough."
"True—true," I replied; "and, indeed, I had no intention of alarming you unnecessarily—but you should use all proper caution. A draught of this Medoc will defend us from the damps."
Here I knocked off the neck of a bottle which I drew from a long row of its fellows that lay upon the mould.
"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."
"And I to your long life."
He again took my arm, and we proceeded.
"These vaults," he said, "are extensive."
"The Montresors," I replied, "were a great and numerous family."
"I forget your arms."
"A huge human foot d'or, in a field azure; the foot crushes a serpent rampant whose fangs are imbedded in the heel."
"And the motto?"
"Nemo me impune lacessit."
"Good!" he said.