Lurking Predators is a rare Enchantment card from Magic 2010 (M10), collector number 190. Current market price: $18.45 (foil $57.58), TCGplayer market prices via Scryfall.
Whenever an opponent casts a spell, reveal the top card of your library. If it's a creature card, put it onto the battlefield. Otherwise, you may put that card on the bottom of your library.