Whenever a creature you control becomes monstrous, it fights up to one target creature an opponent controls.

Megamorph {4}{B}{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.)

{5}{B}{G}: Montrosity 3 (If this creature isn’t monstrous, put three +1/+1 counters on it and it becomes monstrous.)