Aeithalides

Aeithalides, a mythical hero, son of Mercury and Eupolemas. was a native of Larissa, who had the liberty from his father in being sometimes with the living and sometimes with the dead, so that he was aware of all that was passing among both. He was a herald of the Argonauts, and the duties of his office gave rise to the fable; he being necessarily often present with, and often absent from, the army, and being obliged to be exactly informed of all that happened.