Of cypress, I roamed with my Soul— Of cypress, with Psyche, my Soul. (lines 11-12)
We don't know about you, but all this disembodied Soul stuff strikes us as pretty weird. Maybe the speaker is hallucinating, or dreaming, or just weaving an elaborate metaphor. Whatever the case might be, his soul has become her own person, and she's a fully developed character in this poem. We learn about her appearance, her feelings, and her relationship with the speaker. That sounds completely supernatural to us.
Out of which a miraculous crescent Arose with a duplicate horn— (lines 35-36)
We've already heard about ghouls and souls that walk around on their own. Now, all of a sudden, a goddess appears in the poem. She's not a character the way Psyche is, since she never talks or interacts with the speaker. It's not even quite clear, in this moment, if the speaker is really seeing something like a goddess or just looking at the planet Venus and imagining Astarte. Poe's poems are filled with guys who read too much and have hyperactive imaginations. Maybe this guy just imagining an ancient goddess.
To point us the path to the skies— To the Lethean peace of the skies— (lines 45-46)
Our speaker drops mythological references all over the place. This one is important, and kind of complicated too. On the one hand, he seems to be imagining something like the Christian heaven – a peaceful place in the sky. On the other hand, he calls that peaceful place "Lethean." That's a reference to the river in the underworld in Greek mythology.