Conundrum Sphinx is a rare Creature — Sphinx card from Magic 2011 (M11), collector number 51. Current market price: $0.25 (foil $0.41), TCGplayer market prices via Scryfall.
Flying Whenever this creature attacks, each player chooses a card name. Then each player reveals the top card of their library. If the card a player revealed has the name they chose, that player puts it into their hand. If it doesn't, that player puts it on the bottom of their library.