Relentless Reveler

Riot (This creature enters the battlefield with your
choice of a +1/+1 counter or haste.)
When Relentless Reveler enters the battlefield,
it deals damage equal to its power to target
creature.
Undying (When this creature dies, if it had no
+1/+1 counters on it, return it to the battlefield under
its owner's control with a +1/+1 counter on it.)