XFACTOR
Set to 4 different clues across 5 published puzzles, most often “Unknown element” — The New York Times, Sunday, 28 May 2006.
7 letters
Every clue on record, most used first
- Unknown element2 times
The New York Times — Sunday, 28 May 2006
- Mystery quality ... or what 18- and 55-Across and 3- and 32-Down have?once
The New York Times — Monday, 26 October 2009
- Hard-to-define influenceonce
The New York Times — Friday, 13 March 2009
- Unknownonce
The New York Times — Sunday, 1 October 2006