Beatrix, Cloud Rider

+3: Take the top two cards of your library. Put any instants or creatures into your hand. Put the remaining in your graveyard.
-X: Give X amount of creatures flying until end of turn. Untap all creatures with flying and give them haste and vigilance.
-7: Exile target creature you control. Place a 10/10 Beatrix's Roc onto the battlefield with flying and trample. Tap one enemy creature.