Alliteration brings the poem's metaphors and images to life on the page, helping to conjure an eerie atmosphere.
Take, for example, the sinister episode in which the bandaged soul is accosted and fondled by "some ghastly Fright"—a soul-deep terror. The Soul is a delicate creature, and the "Goblin" that caresses her takes grotesque enjoyment in her suffering. Alliteration captures both the soul's fear and the Goblin's pleasure:
She feels some ghastly Fright come up
And stop to look at her —
Salute her, with long fingers —
Caress her freezing hair —
Sip, Goblin, from the very lips
The Lover — hovered — o'er —
The emphatic /f/ sounds in lines 3-6 draw attention to the "Fright" and its awful touch; the alliterative /h/ in line 6, meanwhile, suggests the Soul's shallow, frightened breathing. The /l/ sound has a lip-smacking quality that fits with the /p/ consonance in "Sip" and "lips," making it sound as if the Goblin is savoring every moment.
But the Soul doesn't only suffer. It also enjoys "moments of escape." These joyous, wild times are like an explosion, evoked by the alliterating /b/ sounds in stanzas 3 and 4:
The soul has moments of escape —
When bursting all the doors —
She dances like a Bomb, abroad,
And swings upon the Hours,
As do the Bee — delirious borne —
These plosive /b/ sounds are like little bursts of color and light, embodying the soul's unleashed happiness during her all-too-brief moments of release.
Before too long, though, the Soul is "retaken" by the same frightful "Horror" that accosted it in the first part of the poem. In the last two stanzas, the /s/ alliteration in "staples" and "song" recalls the sibilant consonance of the second stanza, creating an unsettling whispery hush that matches the Soul's own helpless silence. And the alliterative "Horror" and "her" in line 23 bring back that frightened gasping sound.