The Pursuer

When The Pursuer deals combat damage to an opponents creature you may pay {3}. When you
do, that creature gets a -1/-1 counter on it and
you put a +1/+1 counter on The Pursuer.
At any time you may remove any number of
+1/+1 counters from the Pursuer to deal damage
equal to the number of counters removed this
way to target creature an opponent controls or to target opponent.