Cheapest priced copy (Duel Decks: Elspeth vs. Tezzeret): $0.35 at Card Kingdom, near mint, their price list as of .
Mosquito Guard 
Creature — Kithkin Soldier · 1/1 · Common · Morningtide · #18
First strike
Reinforce 1—{1}{W} ({1}{W}, Discard this card: Put a +1/+1 counter on target creature.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Elspeth vs. Tezzeret | 6 | Common | $0.35 | — |
| Morningtide | 18 | Common | $0.35 | $0.49 |