Wizened Arbiter is a rare Creature — Human Soldier Wizard card from Mystery Booster Playtest Cards 2019 (CMB1), collector number 14. Current market price: $0.68, TCGplayer market prices via Scryfall.
When Wizened Arbiter enters, you may reveal a white card you own from outside the game. If you do, exchange that card with a card in your hand.