Stiflenought wins by resolving a 1-mana 12/12 Phyrexian Dreadnought and protecting it, so the second Annul helps stop the Dreadnought itself or a key artifact like Powder Keg before it locks the game. Circle of Protection: Red is dead weight here since the opponent is mono-blue, so skip it; instead prioritize Standstill, Prohibit, and Counterspell to control the tempo. Mana Leak is excellent since they run almost no fast mana to pay the tax. Swords to Plowshares remains your best single answer to a landed Dreadnought, so keep all four.