The Actualizer is a rare Legendary Creature — Human Wizard card from Unknown Event (UNK), collector number RZ03h. Current market price: $15.72, TCGplayer market prices via Scryfall.
At the beginning of your first main phase, read aloud the name, mana cost, type line, power, and toughness of a card in your hand, except lie about one of them. Each opponent simultaneously guesses which one is incorrect. Then reveal the card. Each opponent who guessed incorrectly loses 3 life. You may discard that card and draw a card. (They can't look it up or ask for help as this ability is resolving. Nice try, though.)