In the poem "The Splendour Falls," Tennyson uses a variety of literary devices.
Alliteration is seen with "snowy summits," "long light," and "blow, bugle, blow" (the last which might also be repetition).
Consonance is seen with "thinner, clearer, farther" and "falls, castle walls."
"Shakes" and "lakes" has both assonance and consonance.
Assonance is evident with "far...scar" (which is also consonance).
Personification is seen in several places with examples like "long light shakes," "cataract leaps in glory," and "purple glens replying."
Repetition is also found in several places: "dying and dying and dying" (found in two places in the poem), "blow...let us blow," "blow, bugle, blow," "soul to soul," and "forever and forever." "
"O hark, O hear" may be considered repetition, but the words "hark" and "hear" also include alliteration and consonance.
All the descriptions of personification (which are specific) are examples of imagery, which is the general label for devices like personification, hyperbole, similes, metaphors, etc.
The use of Tennyson's words that create an irregular rhyming pattern give the poem a musical quality, which adds to the mood and tone of the poem: it is bright and uplifting as it praises nature.