Amulet Titan relies on cheap enablers (Arboreal Grazer, Amulet of Vigor, Summoner's Pact at zero mana) and wants to chain many spells per turn, so Trinisphere taxes every one of those cheap plays up to three mana while our Tron lands and colorless-costed spells are barely affected. Chalice of the Void set to zero shuts off Summoner's Pact and other free spells, and Karn, the Great Creator can wish for the second Trinisphere from the sideboard once the first resolves since we have two copies here. We trim Dismember, since their early creatures (Arboreal Grazer) are low-impact targets and we'd rather tax their whole gameplan than spot-remove a single body, and one Giant's Boulder for being a slower mana rock in a matchup we want to win through disruption, not a long grind.