Protean Hydra

This creature enters with X +1/+1 counters on it. If damage would be dealt to this creature, prevent that damage and remove that many +1/+1 counters from it. Whenever a +1/+1 counter is removed from this creature, put two +1/+1 counters on it at the beginning of the next end step.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6og7u2bmz1pb1h9a5vsa8q.