Doomsday wins by assembling a five-card stack via Doomsday and combo-killing with Thassa's Oracle or Lion's Eye Diamond loops, and while Leyline of the Void doesn't stop the Doomsday pile itself (cards go to exile via the spell's own effect, not the graveyard), it does shut off Street Wraith's cycling-fueled graveyard interactions and any Flashback-adjacent recursion, though its main value here is more limited than in true reanimator matchups. Chalice of the Void set to 1 is our best tool, locking out Dark Ritual, Ponder, and Brainstorm, while on 0 it locks out Lotus Petal and Doomsday's own zero-cost interactions with fast mana. We trim Chrome Mox since our own colored cards are largely unnecessary fuel and the opponent's Force of Will/Daze punishes over-extension; prioritize fast starts with Simian Spirit Guide and Ancient Tomb to close before they assemble their combo.