Annul is excellent here, countering Enchantress's Presence, Solitary Confinement, Sterling Grove, or any of the other enchantments that feed Serra's Sanctum before they lock in their engine. Thwart is awkward in this matchup: you either pay four mana or return three Islands, which is a steep cost for a deck that out-values you on card advantage once its engine starts, so prioritize cheap proactive answers. Hydroblast stays in the sideboard because the opponent has no red cards for it to target. Stasis remains your trump card, since players skip their untap steps and their lands, including Serra's Sanctum, stay tapped once used.