Guardian Shield-Bearer
Creature — Human Soldier
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 Guardian Shield-Bearer is turned face up, put a +1/+1 counter on another target creature you control.
Illustrated by
Dragons of Tarkir#189CommonEnglishLegality
Rulings
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.
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.
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.