This matchup is a race to either resolve Doomsday under your counterspells or counter it, and the critical moment is always the Thassa's Oracle triggered ability — Consign to Memory answers that trigger directly and cannot be circumvented by Cavern of Souls, making it your most important sideboard card here. Null Rod shuts off Lion's Eye Diamond and Lotus Petal, taxing their fast mana and forcing them to fight through your interaction on natural mana, which heavily favors your Daze. Pyroblast is excellent in this slot, hitting Force of Will, Brainstorm, Ponder, Tamiyo, Inquisitive Student, and Thassa's Oracle as a permanent (though prefer Consign to Memory for the Oracle trigger itself). Apply early pressure with Dragon's Rage Channeler and Cori-Steel Cutter to force them to combo before they've set up optimally; Boomerang Basics and Flow State are too slow and passive for this gameplan, and Lightning Bolt is largely dead without enough relevant targets beyond Tamiyo.