How ore essential & nonessential clauses different?

Read the excerpt from "annabel lee," by edgar allan poe. and this was the reason that, long ago, in this kingdom by the sea, a wind blew out of a cloud, chilling my beautiful annabel lee; so that her highborn kinsmen came and bore her away from me, to shut her up in a sepulchre in this kingdom by the sea. how does the rhythm of the excerpt support the theme of the poem? the rhythm changes on the phrase “a kingdom by the sea,” emphasizing poe’s distrust of a monarchy. the rhythm changes on the phrase “bore her away from me,” emphasizing poe’s desire to be reunited the rhythm changes on the words “chilling” and “sepulchre,” emphasizing poe’s complaint about unexpected death. the rhythm changes on the words “lee” and “me,” emphasizing poe’s fear that his bond with his love is fragile.