Artasskil, The hydra king

Treat the power and toughness of all your creatures as if they were +1 counters instead of normal power and toughness, and are hydra creature in addition to their other types.
{3}{g}{g}{x}{t}: Put {x} +1/+1 counters on all creatures you control that are hydra creatures.
Why fear hydras when you can become one?