Hidden Dragonslayer [Dragons of Tarkir Pre-Release]
:
Lifelink
Megamorph {2}{W}
(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 Hidden Dragonslayer is turned face up, destroy target creature with power 4 or greater an opponent controls.