Swell of Courage is a uncommon Instant card from Duel Decks: Elspeth vs. Tezzeret (DDF), collector number 31. Current market price: $0.33, TCGplayer market prices via Scryfall.
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.)