Cheapest priced copy (Modern Horizons): $0.35 at Card Kingdom, near mint, their price list as of .
Zhalfirin Decoy 
Creature — Human Soldier · 1/3 · Uncommon · Modern Horizons · #39
{T}: Tap target creature. Activate only if you had a creature enter the battlefield under your control this turn.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Horizons | 39 | Uncommon | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 14 June 2019Zhalfirin Decoy’s ability can be activated even if a creature entered the battlefield under your control only before Zhalfirin Decoy entered the battlefield, and even if that creature has left the battlefield.