Sorin, the Eternal Thirst

+2: You gain 1 life for each vampire you control, your opponent loses 1 life
-4: Sacrifice two creatures, you gain life equal to their combined power, your opponent loses life equal to life gained this way
-7: create 7 1/1 vampire creature tokens with lifelink, vigilance, and flying, then, if you control 20 or more vampires, your opponent loses the game