Devoted Combo relies heavily on a glut of nonbasic lands (Verdant Catacombs, Windswept Heath, Overgrown Tomb, Godless Shrine, Temple Garden) and on Leyline of Abundance-fueled mana, so Blood Moon turning all their nonbasics into Mountains can badly strand their mana base. Galvanic Blast cleanly answers Delighted Halfling, Devoted Druid, or Birds of Paradise before they go off, so we bring in all three copies. Vexing Bauble stays in the sideboard because it only counters spells cast with no mana spent, and Devoted Combo's main deck doesn't cast spells that way. Preordain and the single copies of Emry and Sink into Stupor are cut since we need proactive disruption and mana denial rather than card selection against a combo deck that can win out of nowhere.