Historical clue formulations

• Largest moon of Pluto — 2018-03-16
• Styx ferryman — 2012-04-18
• Underworld figure — 2003-01-25
• Soul transporter — 2002-06-27
• Styx ferryman — 1999-12-12
• Mythical character in "The Inferno" — 1998-06-20
• Styx ferryman — 1997-12-14
• Styx ferryman — 1994-10-12