Devoted Combo relies on fetchlands (Verdant Catacombs, Windswept Heath) and a handful of nonbasic duals to assemble Devoted Druid plus Vizier of Remedies for infinite mana, so Blood Moon turns their fetched lands into Mountains and can strand their mana engine, though it won't stop a Devoted Druid/Vizier combo that's already resolved with basics in play. Enter the Avatar State can push through lethal or protect our key attacker from a Fatal Push-style removal spell they bring in postboard. We cut our weakest, most situational cards to bring in proactive mana disruption against their combo-reliant manabase.