Heroic Defiance is a common Enchantment — Aura card from Planeshift (PLS), collector number 6. Current market price: $0.04 (foil $3.64), TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature gets +3/+3 unless it shares a color with the most common color among all permanents or a color tied for most common.