Mage of ice ember

Coldblood {1}{u}{u} (you may play this card for it's coldblood cost if it is the first spell you cast this turn and no spells were cast last turn.)
When Mage of ice ember enters the battlefield, if you paid it's coldblood cost, tap target creature an opponent controls. that creature does not untap for as long as you control Mage of ice ember.
{2}{u}{u}: tap target creature.