Mirror-Mad Phantasm is a mythic Creature — Spirit card from Innistrad (ISD), collector number 68. Current market price: $0.76 (foil $7.82), TCGplayer market prices via Scryfall.
Flying {1}{U}: This creature's owner shuffles it into their library. If that player does, they reveal cards from the top of that library until a card named Mirror-Mad Phantasm is revealed. The player puts that card onto the battlefield and all other cards revealed this way into their graveyard.