Stanza 1 has imagery of a magical kingdom, perhaps like the legendary King Arthur in England since "the sea" is mentioned. Annabel Lee is also a legendary maiden: "[one] whom you may know."
Other imagery: The winged seraph in stanza 2, wind, cloud, and sepulcher in stanza 3, and the demons down under the sea, bright eyes, nighttide, sepulcher/tomb in stanzas 5 and 6
Assonance: vowels a and o and long i in all stanzas; stanza 3 has the i sound: wind, this, highborn, kinsmen
Alliteration: stanza 1 with the repetition of the initial m in lines 2 and 3 l and b in line 6; the initial c in l. 7; l in line 8; lines 17 and 21 repeat h ; (here the h suggests wind) w is repeated in line 29; d in l. 31;s in ll. 32 and 39;s in lines 40 and 41. (You may wish to find more.)
The word child in line 7 denotes the youth of the lovers, and is a metaphor for the innocence of their love. In lines 9-12, the relationship between the husband and bride is compared to a heavenly one: "We loved with a love that was more than love..." The envy of angels, "winged seraphs" elevates this love. In stanza 6 the moon and stars are compared to messengers.
There are two allusions: "demons under the sea"-Greek myth of Andromeda threatened by a sea monster, but rescued by Perseus; "ever dissever" and "soul" -St. Paul's epistle to the Romans about nothing separating us from God's love.