Lurna, the Brood Mother

Lurna, the Brood Mother enters the battlefield
with a number of +1/+1 counters on it equal
to the amount of mana spent to cast it.
{1}{b}: Regenerate target Hydra creature.
{2}{g}{g}, {t}: Double the number of +1/+1
counters on each Hydra creature you control.
If two heads are better than one, seven must be great