Oketra's Avenger is a common Creature — Human Warrior card from Hour of Devastation (HOU), collector number 17. Current market price: $0.04 (foil $0.26), TCGplayer market prices via Scryfall.
You may exert this creature as it attacks. When you do, prevent all combat damage that would be dealt to it this turn. (An exerted creature won't untap during your next untap step.)