Perhaps the most prominent poetic device used in "The Raven" is alliteration. This use of alliteration seems to thrust the poem forward, as if hastening to a conclusion. Good examples are:
And the silken, sad, uncertain...
...filled me with fantastic terrors...
The most brilliant use of alliteration in all poetry is to be found in these lines:
Then, methought, the air grew denser, perfurmed from an unseen censer
Swung by seraphim whose foot-falls tinkled on the tufted floor.
The "s" sounds begin with "denser" and recur in "unseen," "censer," "Swung," and "seraphim." They are followed in the second line by "f" sounds in "foot-falls" and by "t" sounds in "tinkled" and "tufted."
There are many internal rhymes throughout the poem, beginning with:
Once upon a midnight dreary, while I pondered, weak and weary...
Poe uses similes and metaphors throughout "The Raven." For example:
...and his eyes have all the seeming, of a demon's that is dreaming...
Poe's major contribution to poetry was in his symbolism. The raven obviously symbolized death. The French, especially through Charles Baudelaire, were so capitivated by the innovation that "symbolisme" became a major movement in French poetry. Poe explains his theory of poetry with special attention to his composition of "The Raven" is an essay titled "The Philosophy of Composition" (see reference link below).
Further examples of alliteration—the repetition of an initial consonant sound—include "Deep into that darkness peering, long I stood there wondering, fearing, / Doubting, dreaming dreams no mortal ever dared to dream before" (these lines repeat the "d" sound, almost drumming on it, to help create the mood of ominousness and inevitability). Another example of alliteration: "And the only word there spoken was the whispered word, 'Lenore!' / This I whispered, and an echo murmured back the word, 'Lenore!'" The alliteration of the "w" sound is much softer compared to the alliteration of the "d" sound in the lines immediately preceding it. Going from the repetition of such a loud sound to the repetition of such a soft sound makes the softer sound seem a little spooky in this case.
Also, the raven is described as "ebony"—a color often symbolically associated with death, especially in Poe's stories. Given the narrator's preoccupation with death, especially that of his lover, as well as his belief that the raven has come from either the Underworld, the devil, or heaven, seem to confirm this symbolism. He also personifies the raven, insisting that he has some "lordly name" in the Underworld, and thinking that "his soul in that one word he did outpour."