Slayer of Worlds

When you Cast Slayer of Worlds, draw a card and
lose 1 life.
{w/b}, {p/b}: Each opponent loses 1 life and sacrifices a creature.
{w/b}{p/w}: You gain 1 life for each opponent and draw
a card.
{w/b}{w/b}{p/w}{p/b}: Each opponent sacrifices a creature.
You gain life equal to the sacrificed creatures' toughness.