Mono-Blue Faeries relies on cheap flash tempo creatures like Spellstutter Sprite and Brinebarrow Intruder alongside Counterspell to protect its clock, so proactive disruption is valuable before their permission comes online. Duress can strip a Counterspell or Of One Mind out of hand before they set up, though it can't touch their creatures once cast. Fog remains the backbone of this matchup since Faerie Miscreant, Moon-Circuit Hacker, and Ninja of the Deep Hours all deal damage exclusively through combat, so keep the full Moment's Peace and Weather the Storm suite. This is a favorable matchup as long as you keep resolving Fog effects and grinding card advantage past their small flyers.