Polukranos, World Eater
{2}{G}{G}
Legendary Creature -- Hydra
5/5
{X}{X}{G}: Monstrosity X. (If ~this~ isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When ~this~ becomes monstrous, it deals X damage divided as you choose among any number of target creatures your opponents control. Each of those creatures deals damage equal to its power to ~this~.