Mage's Attendant is a uncommon Creature — Cat Rogue card from Streets of New Capenna (SNC), collector number 21. Current market price: $0.27 (foil $0.38), TCGplayer market prices via Scryfall.
When this creature enters, create a 1/1 blue Wizard creature token with "{1}, Sacrifice this token: Counter target noncreature spell unless its controller pays {1}."