Creatures with power less than Den Protector's power can't block it.
Megamorph {1}{G}
(You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)
When Den Protector is turned face up, return target card from your graveyard to your hand.