How does Edgar Allan Poe create the mood of melancholy in this excerpt of his poem, "The Raven"? "Deep into the darkness peering, long I stood...

There are many devices which make this excerpt "melancholy," but I will focus on two: imagery and sound.

First, the imagery presented draws a dark and mournful picture in the reader's mind's eye. Words like darkness give the impression of grief and loss, and this diction combines with our second factor, sound, to give the reader the general indication of sadness.

Sound, as used by Poe in this excerpt, is intentionally meant to sound like a funeral dirge. Think of words like "Lenore, before, and more." All three have the drawn out sound of the short "O" combined with a hard "R."  This is done intentionally, as Poe was using the sound of language to connote grief, much like a sad piece played on a pipe organ. Had he used words like "bright, flight, sight, and might," those words would have carried a cleaner and altogether happier sound. As it is, however, Poe uses the above tools, imagery and sound, to let his readers know of his intimate sadness.