Cheapest priced copy (Rivals of Ixalan): $0.35 at Card Kingdom, near mint, their price list as of .
Swift Warden 
Creature — Merfolk Warrior · 3/3 · Uncommon · Rivals of Ixalan · #146
Flash
When this creature enters, target Merfolk you control gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rivals of Ixalan | 146 | Uncommon | $0.35 | $0.49 |