Cheapest priced copy (Duel Decks: Elspeth vs. Tezzeret): $0.35 at Card Kingdom, near mint, their price list as of .
Swell of Courage 
Instant · Uncommon · Morningtide · #26
Creatures you control get +2/+2 until end of turn.
Reinforce X—{X}{W}{W} ({X}{W}{W}, Discard this card: Put X +1/+1 counters on target creature.)
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Elspeth vs. Tezzeret | 31 | Uncommon | $0.35 | — |
| Morningtide | 26 | Uncommon | $0.35 | $0.49 |
| The List | MOR-26 | Uncommon | $0.35 | — |