Feat of Resistance is a common Instant card from Core Set 2021 (M21), collector number 19. Current market price: $0.27 (foil $0.17), 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.)