Assault Formation is a rare Enchantment card from Dragons of Tarkir (DTK), collector number 173. Current market price: $0.42 (foil $2.20), TCGplayer market prices via Scryfall.
Each creature you control assigns combat damage equal to its toughness rather than its power. {G}: Target creature with defender can attack this turn as though it didn't have defender. {2}{G}: Creatures you control get +0/+1 until end of turn.