The main figure of speech is ekphrasis, which is extended description. The poem tends to employ many similes, i.e. explicit comparisons signalled by the term "like", and a fair amount of hyperbole, i.e. overstatement used to give a sense of superlative. The religious symbolism functions as a series of allusion. Some of the internal speeches can be considered forms of apostrophe, or direct address.
Describing hair yellow as corn – simile.
Eyes deeper than water – hyperbole, or overstatement.
Day as 10 years – hyperbole
Souls like thin flames – simile
Strove-steps-side – alliteration
Speaking leaf: personification
spins like a midge – another simile
face … Nothing – possibly an anacolouthon