Doomsday is a dedicated combo deck setting up a Thassa's Oracle win through Dark Ritual and Lion's Eye Diamond, so proactive disruption and free countermagic are critical. Force of Negation stops their Doomsday sorcery itself or any other noncreature combo piece even when we're tapped out, and the extra copies ensure more consistent access. Consign to Memory answers their colorless artifacts like Lotus Petal or Lion's Eye Diamond that enable the combo. Back to Basics does little against a deck that can win through a single land and doesn't rely on heavy nonbasic value; Gandalf and Forth Eorlingas! are too slow to matter against a deck trying to win outright before combat.