Doomsday is a pure combo deck trying to assemble a kill with Thassa's Oracle, so Surgical Extraction can proactively exile their Thassa's Oracle or Lion's Eye Diamond from their library once revealed via your own cantrips, crippling their only outs. Force of Negation is essential to counter their Doomsday sorcery itself for free on their turn before they pile their library. Meltdown can answer their Lotus Petal and Lion's Eye Diamond mana rocks at X=0, slowing down their ritual-fueled combo turn. Into the Flood Maw and Spell Pierce are cut since they don't interact meaningfully with the combo's core pieces, and the extra Unholy Heat/Preordain are trimmed since proactive disruption matters far more than card selection here.