Lifegain wants to chain life-gain triggers through Hinterland Sanctifier, Haliya, and Case of the Uneaten Feast to fuel Amalia Benavides Aguirre's explore ability and Lunar Convocation's drain, so we want cheap interaction and graveyard hate. Rest in Peace exiles cards instead of letting them hit the graveyard, which shuts off Case of the Uneaten Feast's solved ability (it gives creature cards in the graveyard the ability to be cast) and Moseo's infusion reanimation. Negate is strong against their noncreature spells like Lunar Convocation, Case of the Uneaten Feast, Ajani Resolute, and Erode. Seam Rip stays in at full count, because it hits much of their deck: Case of the Uneaten Feast (mana value 1), Lunar Convocation (mana value 2), Hinterland Sanctifier, Liliana the Faultless, Enlightened Confidant, Amalia Benavides Aguirre, Ajani Resolute, and Starscape Cleric are all mana value 2 or less. To make room we trim Thror's Map, The Fire Crystal, and The Enigma Jewel, which do little to interact with their lifegain engine.