Hagmaw, Sacrificial Brewer

Whenever you sacrifice a creature you may
pay {b}{b}. If you do, destroy target creature
an opponent controls with CMC 4 or less.
{t}, sacrifice a creature: add {b}{b}
to your mana pool.
{t}, sacrifice 2 creatures: draw 2 cards
{t}, sacrifice 3 creatures: each opponent
sacrifices 2 creatures
{t}, sacrifice X creatures: put X -1/-1
counters on each other creature