Mono-Blue Stiflenought has no red spells or permanents, so Blue Elemental Blast and Hydroblast are dead, while Naturalize can target their Phyrexian Dreadnoughts as well as Powder Keg. This matchup is decided by the Daze and Mana Leak war over their Phyrexian Dreadnought and Stifle-based combo, so the maindeck's countermagic stays in unchanged (though Wasteland cannot target their basic lands for Gush/Foil alternate costs). Prioritize using Survival of the Fittest to find Gilded Drake as a one-sided answer to a resolved Phyrexian Dreadnought, since it exchanges itself for their 12/12. Careful Study and Frantic Search should be sequenced to hold up Daze mana whenever possible.