Mythos of Vadrok is a rare Sorcery card from Ikoria: Lair of Behemoths Promos (PIKO), collector number 127s. Current market price: — (foil $0.45), TCGplayer market prices via Scryfall.
Mythos of Vadrok deals 5 damage divided as you choose among any number of target creatures and/or planeswalkers. If {W}{U} was spent to cast this spell, until your next turn, those permanents can't attack or block and their activated abilities can't be activated.