Oops! All Spells is a turn-1 combo deck that wins by milling its library with Balustrade Spy or Undercity Informer, then reanimating Thassa's Oracle via Dread Return with Narcomoeba sacrifice fodder. Leyline of the Void is your best card — a free opening hand Leyline completely shuts off Dread Return and exiles Narcomoeba as they mill, gutting the combo entirely. Deafening Silence prevents them from casting multiple noncreature spells in a turn, stopping Dark Ritual and Cabal Ritual chains that power out the combo. Containment Priest exiles any creature that would enter from the graveyard, providing a redundant lock piece that also puts a body on board. Static Prison, Goblin Bombardment, and some Sand Scouts come out as they offer no interaction with a deck that doesn't attack or use permanents meaningfully — prioritize your fast disruptive pieces to race their turn-1 kill.