Possible Clues:

• Hell in the shade
• Master of Cerberus
• Centre of emphasis of the Parisian underworld
• It was guarded by a three-headed dog
• Headless ghosts in the underworld
• Charon's locale
• In Greek mythology, the underworld abode of the souls of the dead
• He is around with his father back there, and to hell with two of them (5)
• Underworld of Greek mythology
• Perhaps he'll be like this?