Dimir Tempo lives and dies by its cantrips (Brainstorm, Ponder) and extra card draws off Tamiyo, Inquisitive Student and Kaito, Bane of Nightmares, so Hullbreacher punishes every one of those extra draws by turning them into Treasures for us instead. Barrowgoyf comes in as a resilient deathtouch/lifelink threat that grows with graveyard fuel from both sides and dodges their Fatal Push at low card-type counts early while still being a house late. We trim Waterlogged Teachings and Expedition Map since we don't need to dig for lands as badly against a deck without much mana denial beyond Wasteland, and cut an Island since Hullbreacher and Barrowgoyf lower our overall land count needs slightly. Play around Force of Will and Daze on their turns and prioritize resolving Karn, the Great Creator or The One Ring behind protection.