Poe uses a number of literary devices in "The Lake" (also called "The Lake-To--" in other texts). Poe uses metaphor in the very first line ("In the spring of my youth it was my lot"). Here, the speaker describes the beginnings of his youth as his "spring." In describing this time of youth as his spring, the reader gets the sense of a time of awakening: as the trees and natural world awake from the winter slumber.
Poe also uses alliteration to emphasize his love of the environment around and including the lake. The repetition of words beginning with "L" connect ideas of love, loneliness, and the lake.
The which I could not love the less--
So lovely was the loneliness
Of a wild lake, with black rock bound
The speaker presents an interesting combination characteristic of Poe's Gothic world of romance and dark images. The lake is wild but the scene fills the speaker with love and loneliness.
In the second stanza, the speaker personifies Night as if Night were a person who had come to change the environment around the lake, transforming it into something more striking in terms of "terror" and loneliness. Again, the speaker (Poe) combines feelings of terror and "delight" ("not fright") indicating the scene was exciting and an awakening rather than something to be feared.
The rhyming of the poem adds something as well. Just as the speaker is spellbound by the scene and experience, the poem itself could also read like a spell or an incantation about the transformative power of experiencing nature in its different manifestations. In other words, the speaker describes how he was affected/spellbound by the scene and the poem itself is an attempt to affect/cast a spell on the reader, at least in terms of making the reader think.
In the final stanza, the speaker repeats/concludes the idea that it is the loneliness (the "solitary soul") that can imagine such a "dim lake" in terms of a kind of Eden. Here the speaker makes a literary reference, an "allusion," to the Bible and the story of the Garden of Eden. A reader aware of this Biblical story is then given the opportunity to think of how the speaker's experience at the lake (in his youth) is similar/different from Adam's and Eve's experience in the Garden of Eden.