7 cards where the card is tagged “face-down-peek”

Aven Soulgazer (Onslaught #8)
Keeper of the Lens (Dragons of Tarkir #240)
Lens of Clarity (Khans of Tarkir #223)
Lumbering Laundry (Murders at Karlov Manor #253)
Revealing Wind (Dragons of Tarkir #197)
Smoke Teller (Khans of Tarkir #151)
Spy Network (Onslaught #115)

This search is finished. Now the real work can begin.