Cheapest priced copy (Bloomburrow): $0.35 at Card Kingdom, near mint, their price list as of .
Treeguard Duo 
Creature — Frog Rabbit · 3/4 · Common · Bloomburrow · #200
When this creature enters, until end of turn, target creature you control gains vigilance and gets +X/+X, where X is the number of creatures you control.
Legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Bloomburrow | 200 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 26 July 2024The value of X is determined only as Treeguard Duo’s triggered ability resolves, potentially including Treeguard Duo itself. It won’t change later in the turn if the number of creatures you control changes.