Champion of Rhonas is a rare Creature — Jackal Warrior card from Amonkhet (AKH), collector number 159. Current market price: $0.23 (foil $0.58), TCGplayer market prices via Scryfall.
You may exert this creature as it attacks. When you do, you may put a creature card from your hand onto the battlefield. (An exerted creature won't untap during your next untap step.)