Mono-Blue Faeries is entirely blue, so Pyroblast is a premium sideboard card that counters their Counterspell, Snap, or Of One Mind, or destroys a resolved threat like Spellstutter Sprite or Moon-Circuit Hacker. Skred is weak here since their creatures are mostly small evasive fliers and our snow-permanent count is often too low early to reliably kill them, so cut three copies for Pyroblast. Keep Counterspell and Dispel to fight through their Counterspell and Snap disruption package, and lean on Murmuring Mystic to build a blocking army of Bird tokens against their fliers. Ephemerate is especially valuable here to dodge Snap and re-trigger Augur of Bolas or Mulldrifter for extra card advantage in the grind.