Thirsty Nightstalker

When Thirsty Nightstalker enters the battlefield, each opponent may sacrifice a creature. For each opponent that didn't, put two +1/+1 counters on Thirsty Nightstalker.
Lifelink, deathtouch
Madness {2}{b}{b} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)