Dai Li Agents (214) - Avatar: The Last Airbender

When this creature enters, earthbend 1, then earthbend 1. (To earthbend 1, target land you control becomes a 0/0 creature with haste that's still a land. Put a +1/+1 counter on it. When it dies or is exiled, return it to the battlefield tapped.)

Whenever this creature attacks, each opponent loses X life and you gain X life, where X is the number of creatures you control with +1/+1 counters on them.