Cheapest priced copy (Magic 2010): $5.99 at Card Kingdom, near mint, their price list as of .
Protean Hydra 
Creature — Hydra · 0/0 · Mythic · Magic 2010 · #200
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.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $5.99 to $13.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Magic 2010 | 200 | Mythic | $5.99 | $13.99 |
| Magic 2011 | 194 | Rare | $6.49 | $10.99 |
6 rulings from Wizards of the Coast
- 1 October 2009Protean Hydra’s last ability triggers whenever a +1/+1 counter is removed from it for any reason, not just when a +1/+1 counter is removed by its second ability.
- 1 October 2009All damage that would be dealt to Protean Hydra is prevented, even if it doesn’t have that many +1/+1 counters on it. This is true even if Protean Hydra has no +1/+1 counters on it at all (and is able to remain on the battlefield because some other effect is boosting its toughness). If the amount of damage that would be dealt to Protean Hydra is greater than the number of +1/+1 counters on it, all the +1/+1 counters on Protean Hydra are removed from it.
- 1 October 2009If any +1/+1 counters are removed from Protean Hydra during the end step, its last ability will trigger and set up a delayed triggered ability that will trigger at the beginning of the next end step (which is near the end of the following turn).
- 1 October 2009If multiple +1/+1 counters are removed from Protean Hydra at once, its last ability will trigger that many times.
- 1 October 2009If unpreventable damage is dealt to Protean Hydra, the Hydra’s second ability will try to prevent it and fail (meaning that damage has its normal results), and it will also remove that many +1/+1 counters from Protean Hydra.
- 1 October 2009If a -1/-1 counter is put on Protean Hydra while it has +1/+1 counters on it, that -1/-1 counter and a +1/+1 counter will be removed from it as a state-based action. This will cause Protean Hydra’s last ability to trigger.