Cheapest priced copy (War of the Spark): $0.49 at Card Kingdom, near mint, their price list as of .
Bioessence Hydra 
Creature — Hydra Mutant · 4/4 · Rare · War of the Spark · #186
Trample
This creature enters with a +1/+1 counter on it for each loyalty counter on planeswalkers you control.
Whenever one or more loyalty counters are put on planeswalkers you control, put that many +1/+1 counters on this creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.49 to $1.29 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| War of the Spark Promos | 186s | Rare | — | $1.29Out of stock |
| War of the Spark | 186 | Rare | $0.49 | $0.79 |
2 rulings from Wizards of the Coast
- 3 May 2019If Bioessence Hydra enters the battlefield at the same time as a planeswalker you control, the loyalty counters that planeswalker will receive won't be counted to determine how many counters Bioessence Hydra enters the battlefield with, but they will cause its last ability to trigger.
- 3 May 2019Abilities that trigger when counters are put on a permanent trigger when a permanent enters the battlefield with counters and when a player puts counters on a permanent.