Wildcall is a rare Sorcery card from Fate Reforged Promos (PFRF), collector number 146s. Current market price: — (foil $0.50), TCGplayer market prices via Scryfall.
Manifest the top card of your library, then put X +1/+1 counters on it. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)