Respuesta :
B) Digression
Digression is a stylistic device used in narratives. They are defined as sudden interruptions in the main action or subject of the story to temporary focus on providing background details and/or some character's motivation, to then come back to the main subject of the story.
This is what happens in the excerpt, the narrator starts out describing a "prophet, sprung of Melampus' line of seers", but then they interrupt this description to provide background information about who is Melampus.