(Gain the next level as a sorcery to add its ability.)

Whenever you attack, put a +1/+1 counter on target attacking creature.

2W: Level 2

Whenever a creature you control leaves the battlefield, if it had a counter on it, you gain 2 life.

3W: Level 3

Whenever you cast a spell, put a +1/+1 counter on each creature you control.