Cheapest priced copy (Dragons of Tarkir): $0.35 at Card Kingdom, near mint, their price list as of .
Acid-Spewer Dragon 
Creature — Dragon · 3/3 · Uncommon · Dragons of Tarkir · #86
Flying, deathtouch
Megamorph {5}{B}{B} (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, put a +1/+1 counter on each other Dragon creature you control.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragons of Tarkir | 86 | Uncommon | $0.35 | $0.99 |
3 rulings from Wizards of the Coast
- 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.
- 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.