Possible Clues:

• Imagine not one, perhaps, but many variations
• Something inscrutable
• Mysterious person
• Closing trap, this person spins a mystery
• Conundrum found in game playing
• "Sadeness (Part I)" electronic band
• and 12 Across: Pieces by 21 Down, such as 4 -- and 22?
• Contradictory character
• Elgar's '___ Variations'
• Puzzling problem