Emerson's poem "Brahma" is classified as a lyric. The literary devices he used in the poem include rhyme, imagery, alliteration, and allusion.
In each of the four stanzas, the first and third and the second and fourth lines rhyme for an ABAB rhyme scheme.
Alliteration is the repetition of initial letter sounds, either consonants vowels. Within alliteration are assonance, which is the repetition of vowel sounds that occur within a word, and consonance, which is the repetition of consonant sounds that occur within a word. The first stanza has a lot of "s" and long "a" sounds: slayer, slays, slain, ways.
From the title to the end of the poem, Emerson alludes to Hindu relgious beliefs. The speaker is Brahma himself, or the Over-Soul: "the eternal spirit of creativity and life in the universe, from which all have come and to which all will return." The "strong gods" are subordinate deities who, like mortals, seek union with Brahma. These deities include Yama, "the red slayer," or god of death. The "sacred Seven" are the highest holy persons or saints in Hinduism, who also seek union (or reunion) with Brahma. (See the eNotes commentary linked below.)