Cheapest priced copy (Innistrad: Crimson Vow): $0.35 at Card Kingdom, near mint, their price list as of .
Courier Bat 
Creature — Bat · 2/2 · Common · Innistrad: Crimson Vow · #102
Flying
When this creature enters, if you gained life this turn, return up to one target creature card from your graveyard to your hand.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Innistrad: Double Feature | 369 | Common | $0.59 | $0.99 |
| Innistrad: Crimson Vow | 102 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 19 November 2021Courier Bat's ability will trigger if you gained any amount of life this turn. It doesn't matter if you also lost that much life or more.