Lifegain decks grind through incremental advantage via Amalia Benavides Aguirre, Enlightened Confidant, and Haliya, Guided by Light, so disrupting their key pieces before they take over is critical. Duress can't take their creatures, but it can strip Ajani Resolute, Lunar Convocation, or Erode from their hand, while Negate answers Case of the Uneaten Feast, Lunar Convocation, or Ajani Resolute on the stack. Requiting Hex cheaply answers their mana-value-2-or-less creatures like Enlightened Confidant, Hinterland Sanctifier, or Amalia Benavides Aguirre, and you can blight 1 as an additional cost to gain 2 life. Cut the slower, lower-impact cards like Rapid Rescue, Deceit, and Wistfulness that don't keep pace with their lifegain-fueled card advantage.