Possible Clues:

• Styx ferryman
• Ferryman who brought the souls of the dead across the Styx
• Ferryman of the river Styx
• Pluto's largest moon
• Greek ferry operator casts anchor
• Mythical ferryman
• Boatman of myth
• PLUTO
• Ferryman who brought the souls of the dead across the river Styx
• Ferryman who brought the dead to Hades in Greek mythology