Oops, All Spells! wins by milling its entire library with Balustrade Spy or Undercity Informer—since the deck runs no lands, every card mills—then winning via Thassa's Oracle's enter-the-battlefield trigger, often on turns one or two through Duress and Thoughtseize backup. Containment Priest is your most powerful hate piece: it prevents Narcomoeba from entering the battlefield from the graveyard, denying them the free creatures needed to flashback Dread Return, which effectively locks out their primary win condition as long as the Priest stays in play. Hold up Consign to Memory as your primary counterspell, targeting the mill spell, Dread Return, or Thassa's Oracle itself; Pyroblast and Hydroblast hit Balustrade Spy and Oracle at a cheaper cost and are harder to Pact through since they can't Pact of Negation them twice. After any Oracle or Narcomoeba copy mills into the graveyard, Surgical Extraction permanently seals off their win condition before they can assemble it. Post-sideboard they can pivot to a Goblin Charbelcher plan via Lion's Eye Diamond and Beseech the Mirror, but Force of Will and Consign to Memory answer that line just as cleanly.