Creatures with power less than Den Protector’s power can’t block it.
Megamorph (You may cast this card face down as a 2/2 creature for . 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.
You compare Den Protector's power to the power of any creature trying to block it only as blockers are assigned. Once Den Protector has been legally blocked by a creature, changing the power of either creature won't change or undo the block.
25-02-2015
wotc
Megamorph is a variant of the morph ability. You can find more information on morph on cards with morph from the Khans of Tarkir set.
25-02-2015
wotc
Turning a face-down creature with megamorph face up and putting a +1/+1 counter on it is a special action. It doesn't use the stack and can't be responded to.
25-02-2015
wotc
If a face-down creature with megamorph is turned face up some other way (for example, if you manifest a card with megamorph and then pay its mana cost to turn it face up), you won't put a +1/+1 counter on it.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.