Grakkthar, Bestial Menace

{5}{r}{g}: Monstrosity 4 (If this creature isn't monstrous, put 3 +1/+1 counters on it and it becomes monstrous.)
Whenever a creature you control becomes monstrous, put x +1/+1 counters on that creature, where x equals the number of creatures you control that are monstrous.