Maester Seymour

At the beginning of combat on your turn, put a number of +1/+1 counters equal to Maester Seymour power on another target creature you control.

{3}{g}{g}: Monstrosity X, where X is the number of counters among creatures you control. (If this creature isn't monstrous, put X+1/+1 counters on it and it becomes monstrous.)