Charon's obol was a coin placed in or on the mouth of a dead person before burial.
Greek mythology explain it as a payment or bribe for Charon, the ferryman who conveyed souls across the river Styx that divided the world of the living from the world of the dead.
What happened if the ferryman didn’t get paid? Greek belief argues these souls wander the earth side of the river for hundreds or even thousands of years before they’re permitted to cross.
