Mystery
You can always count on Edgar Allan Poe to be mysterious, that's for sure. Many of his famous stories feature bizarre events that are, ultimately, unexplained. In "The Fall of the House of Usher", for example, a mansion spontaneously implodes, while "The Black Cat" features a mysteriously death-defying black cat. Even Poe's biography is plagued by mystery. His death, for example, is one of the most notorious literary puzzles of all time. He was found dying in an alley, with clothes that weren't his. The exact causes of his death are still, to this day, unknown.
Which brings us to "Alone," a poem that—while not as off-the-wall and gnarly as some of Poe's other works—still has its fair share of mystery. Not only is the word "mystery" a big part of the second half of the poem, we are also left with a bunch of unanswered questions. What is so different about the speaker, for example? What exactly does he mean when he says the mystery was "drawn" from the mountains, fountains, torrents, and everything else under the sun? Poe was the original international man of mystery, but that mystery doesn't always need to involve guys getting buried alive.