The mechanics of oral poetic storytelling are super interesting. Stock tags like “darkness covered his eyes” are chosen by the poet because they have the correct number of syllables to finish the line. The poet would have a number of alternative phrases ready to fit the meter as needed.

There’s even a theory that this mode of extemporaneous oral composition actually requires that the poet be illiterate. The thinking is that it’s a completely different, sound-first approach to language that literacy totally breaks. In order to compose fluently (not recite, the way we understand today), the poet has to understand a phrase like “darkness covered his eyes” as a discrete unit of meaning made up of syllables, not a composition of independent words.