Corosa, Protector of All

Supremacy 4 (You may pay an additional {4} when casting this spell. If you do, this creature enters the battlefield with four +1/+1 counters on it.)
At the beginning of your end step, put a +1/+1 counter on Corosa, Protector of All.
If damage would be dealt to a permanent you
control while Corosa has a +1/+1 counter on it, prevent that damage and remove a +1/+1
counter from Corosa, Protector of All.