Lifegain's plan hinges on resolving engine pieces like Case of the Uneaten Feast, Ajani Resolute, and Lunar Convocation to chain life gain triggers, so Spell Pierce is valuable here: it counters the noncreature engine spells (Case, Ajani, Lunar Convocation, and Erode) while they are cheap enough that they often tap out for them. Spell Pierce cannot hit their creatures like Haliya, Amalia Benavides Aguirre, or Liliana the Faultless, so the Spell Snares stay in to catch their many two-mana plays such as Amalia, Enlightened Confidant, Ajani Resolute, and Lunar Convocation, and Get Out covers creature and enchantment spells. Disdainful Stroke stays on the bench because their mainboard has essentially nothing with mana value 4 or greater. Impractical Joke is a sorcery-speed answer to cheap bodies whose value is mostly in their triggers, so one copy is trimmed, and a copy of the slow Sunderflock goes as well, since the matchup is decided by cheap interaction against a deck of 1-3 mana plays.