Necrotic evolution

Whenever a creature you control dies,
put a +1/+1 counter on target creature.
Whenever a creature an opponent controls dies,
put a -1/-1 counter on target creature.
Whenever a creature with a +1/+1 counter on it
dies, draw a card.
Whenever a creature with a -1/-1 counter on it
dies, its controller loses 2 life.