Frost-Touched War Mage

{u}{u}: Frost-Touched War Mage deals 1 damage to target creature an opponent controls. That creature doesn't untap during its controller's next untap step. If this is the 5th time you have used this ability this turn, put a Frost counter on Frost-Touched War Mage.
As long as there is at least one Frost counter on this creature, you may use the above ability for {2}. At the beginning of your end step, remove a Frost counter from this creature.