The Crimson Avenger is a rare Legendary Creature — Human Wizard card from Unknown Event (UNK), collector number RR10. Current market price: $45.00, TCGplayer market prices via Scryfall.
Flash When The Crimson Avenger enters the battlefield, choose target spell an opponent controls. Reveal cards from the top of your library until you reveal a card that shares a mana value with it. Cast that card without paying its mana cost. Then shuffle your library.