Cheapest priced copy (Jumpstart 2022): $0.35 at Card Kingdom, near mint, their price list as of .
Clockwork Hydra 
Artifact Creature — Hydra · 0/0 · Uncommon · Time Spiral · #253
This creature enters with four +1/+1 counters on it.
Whenever this creature attacks or blocks, remove a +1/+1 counter from it. If you do, it deals 1 damage to any target.
{T}: Put a +1/+1 counter on this creature.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Elspeth vs. Tezzeret | 55 | Uncommon | $0.39 | — |
| Jumpstart 2022 | 135 | Uncommon | $0.35 | — |
| Time Spiral | 253 | Uncommon | $0.35 | $1.99 |
| Time Spiral Remastered | 264 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 19 March 2021If the chosen target is an illegal target by the time Clockwork Hydra's triggered ability tries to resolve, the ability doesn't resolve. You don't remove a counter from Clockwork Hydra.
- 19 March 2021If Clockwork Hydra leaves the battlefield while its trigger is on the stack, you can't remove a +1/+1 counter from it, so it won't deal damage.