When mortals die, their souls must cross the Rivers That Ring the World to reach the Underworld. The shrouded god Athreos is their guide, ferrying the dead to their ultimate rest. Silent, bent, and tattered, he patiently fulfills his role. Athreos cares little for the other gods' conflict with mortals. He is concerned only with safe passage for the dead.
Athreos is never without his signature staff, a gnarled length of dark wood. When the dead arrive on the shores of the Rivers, he lays it across the water to transform it into a barge. His role is the easing the passage from life to death.
The custom on Theros is to craft a funerary mask of clay for the newly dead. In this way, the identities of the deceased are "framed" for Athreos, so that he can mark their proper passage. Such masks are broken into shards called ostraka and used as barter in the Underworld.
She asks pointed questions of the dead who wait for Athreos, learning of life from those who are about to leave it. (Scholar of Athreos)
When Athreos gathers the newly dead to be ferried across the Five Rivers That Ring the World, he sends skeletal griffins to fetch those who stray.
Occasionally the living wander to the Rivers, but the wardens of Athreos ensure that only the dead pass. (Grim Guardian)