Cheapest priced copy (Commander 2016): $0.49 at Card Kingdom, near mint, their price list as of .
Den Protector 
Creature — Human Warrior · 2/1 · Rare · Dragons of Tarkir · #181
Creatures with power less than this creature'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 this creature is turned face up, return target card from your graveyard to your hand.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.49 to $1.29 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 147 | Rare | $0.49 | — |
| Commander 2019 | 161 | Rare | $0.49 | — |
| Dragons of Tarkir | 181 | Rare | $0.69 | $0.79 |
| Murders at Karlov Manor Commander | 169 | Rare | $0.49 | — |
| Dragons of Tarkir Promos | 181s | Rare | — | $1.29 |
4 rulings from Wizards of the Coast
- 25 February 2015You 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 February 2015Megamorph 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 February 2015Turning 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 February 2015If 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.