Feat of Resistance is a common Instant card from The List (PLST), collector number KTK-10. Current market price: $0.23, TCGplayer market prices via Scryfall.
Put a +1/+1 counter on target creature you control. It gains protection from the color of your choice until end of turn. (It can't be blocked, targeted, dealt damage, enchanted, or equipped by anything of that color.)