What sort of narrator does the author employ in "The Fall of the House of Usher"? How does the setting create the mood?

The narrator of this story is one of Roderick Usher's old friends.   Roderick has asked him to come visit, so he obliges.  The narrator is thrown into an almost surreal world of gloom, darkness, and mystery once he arrives at the Usher estate.

The setting is Gothic in nature (Gothic meaning a setting that is usually dark, sometimes frightening, mysterious, and containing mysterious characters, old and spooky houses, etc.).  Poe was one of the kinds of Gothic, in my opinion.  The setting is clearly foreboding, as nothing happy can come out of it. The reader knows early into the story that something dark and mysterious is going on in the Usher home.  Also, the reader senses a feeling of dread reading the story, in anticipation of something bad happening.