Leyline of the Void exiles anything that would go to an opponent's graveyard, so it shuts off the self-mill from Malevolent Rumble and keeps their graveyard empty, which holds down Emrakul's cost reduction (it scales with card types in their graveyard) and Shifting Woodland's delirium. It only affects opponents' graveyards, so our own Unearth, Psychic Frog and Abhorrent Oculus still work off our graveyard as normal. Harbinger of the Seas turns Eldrazi Temple, Urza's Saga, and Ugin's Labyrinth into plain Islands, crippling their colorless ramp. Spell Pierce and Force of Negation can only hit noncreature spells, and their key threats (Emrakul, Devourer of Destiny, Sowing Mycospawn, Basking Broodscale) are all creature spells, so these two are weak here. Keep Fatal Push and Counterspell in to answer Basking Broodscale and Emrakul respectively.

Leyline of the Void is excellent here, cutting off Nethergoyf's growth, its Escape cast, Moonshadow's counter removal, Street Wraith cycling fuel, and Detective's Phoenix's Collect evidence/bestow-from-graveyard line. Toxic Deluge gives a sweeper against their small creature suite (Stitcher's Supplier, Fear of Missing Out, Nethergoyf) when they go wide. Spell Pierce is poor against a deck full of cheap creatures and removal that doesn't mind paying 2. Theorix Charm's counter mode is weak against their low curve, though we keep enough interaction via Fatal Push and Counterspell.

Consign to Memory counters triggered abilities and colorless spells for cheap. Most of their threats are colored spells, and it can't touch Narset's or Teferi's static abilities, so weight it mainly against Solitude's enter-the-battlefield exile trigger, Isochron Scepter's imprint trigger, and Isochron Scepter itself, their only colorless spell. It can't answer the Scepter's activated copy ability, so don't count on it there. Mystical Dispute is cheap, efficient interaction against their blue spells (Teferi, Day's Undoing, Consign to Memory, Jace). Unearth is weak since Solitude and Orim's Chant disrupt our tempo and our 3-or-less creatures aren't the priority reanimation targets against control's removal-light board. Fatal Push struggles vs their lack of early creatures, but Counterspell and Thoughtseize remain premium against their planeswalkers and Wrath of the Skies (Supreme Verdict can't be countered, so Thoughtseize is the better answer there).