Manifest the top card of your library, then put two +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.)
Target creature gains double strike until end of turn. (It deals both first-strike and regular combat damage.)
Ferocious — That creature also gains trample until end of turn if you control a creature with power 4 or greater.