What is the doppelganger in "The Raven" by Edgar Allen Poe?

Here is an article about it:

http://www.poedecoder.com/essays/fissure鈥?/a>



Another source states:

The Doppelganger is a sinister double--a mythic creature who assumes the physical or spiritual likeness of his doomed victim. Along with other literary conventions--the dark, brooding hero, the entombed maiden, the decrepit mansion--Poe borrowed the Doppelganger from the Gothic horror tales of Europe." http://www.buy.com/prod/the-raven-and-th鈥?/a>What is the doppelganger in "The Raven" by Edgar Allen Poe?
Lenore/Raven