Colorless is a prison-combo deck that accelerates into Trinisphere and Karn, the Great Creator to lock you out of the game before deploying massive threats like Emrakul, the Aeons Torn. Null Rod is your most impactful sideboard card here, shutting off Grim Monolith, Candelabra of Tawnos, Voltaic Key, and Manifold Key that power their explosive starts — resolve it early and their engine grinds to a halt. Containment Priest disrupts Urza's Saga's Construct tokens and any reanimation effects, and its flash body lets you hold up interaction. Cabal Therapy is the weakest card in this matchup since their hand is often irrelevant once they've deployed artifacts, and they can rebound through disruption with The One Ring; trimming a Hexing Squelcher rounds out the cuts since your aggressive creature pressure combined with Null Rod is your primary gameplan.