Answer:
A bard. Aegisthus basically killed the bard.
Explanation:
"There was a bard with her, to whom Agamemnon had given strict orders on setting out for Troy, that he was to keep guard over his wife;". Agamemnon gave orders to a serving person, probably a storyteller or singer.
Aegisthus carried this bard off to a desert island and left him there for crows and seagulls to batten upon
