Reality Shift is a uncommon Instant card from Fate Reforged (FRF), collector number 46. Current market price: $0.29 (foil $1.84), TCGplayer market prices via Scryfall.
Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)