Regenerative Hydra

Regenerative Hydra enters the battlefield with 3 +1/+1 counters on it.
If Regenerative Hydra would be dealt combat damage, prevent that damage and remove a +1/+1 counter and put a stump counter on Regenerative Hydra.
At the beginning of your upkeep, you may pay {g}. If you do, remove all stump counters from Regenerative Hydra and put 2 +1/+1 counters on it for each stump counter you removed from Regenerative Hydra