What are the literary elements being used in these quotes from Edgar Allan Poe's "The Raven"? Please explain the quotations. "...Night's Plutonian shore!" "While I nodded, nearly napping, suddenly there came a tapping..." "But the Raven still beguiling my sad fancy into smiling..." "What this grim, ungainly, ghastly, gaunt..."

"...Night's Plutonian shore!" 
The main literary techniques here are allusion and metaphor. Pluto is the god of the dead in Roman mythology. The allusion to Pluto evokes both a sense of deep night and also the fact that the narrator is mourning for the dead Lenore. In terms of metaphor, shore makes one think of a dark ocean at night, something vast and mysterious. 
"While I nodded, nearly napping, suddenly there came a tapping..." 
The devices here are mainly of sound. The phrase "nodded, nearly napping" is an example of alliteration, with repetition of initial "n" sounds. The pair of words "tapping/napping" is an internal rhyme. In the line, the narrator is dozing off and awakened by "a tapping"; the phrasing lets us know that he has not identified the source of the noise yet.
"But the Raven still beguiling my sad fancy into smiling..." 
Again, we see an example of internal rhyme here in "beguiling/smiling." Although the narrator is mourning, he is also enchanted or even obsessed by the raven. By the end of the stanza, though, he begins to take a strong dislike to it.
"What this grim, ungainly, ghastly, gaunt..."
First, this phrase is an example of alliteration, with the repetition of the "g" sounds in "grim, ungainly, ghastly, gaunt." Next, it is an example of hyperbole, or overstatement. It is also to a degree personifying the raven. The narrator is projecting his own misery onto the raven here.