Mono-Blue Faeries is an all-blue tempo/counter deck, so Pyroblast is excellent here, countering their Counterspell, Snap, Spellstutter Sprite, Steel Sabotage, or Hydroblast, or destroying a resolved Moon-Circuit Hacker or Harrier Strix. Envelop counters any of their sorcery-speed card draw like Of One Mind. Annul is a marginal include mainly for Unable to Scream if they bring it in post-board, but it is otherwise weak here. Union of the Third Path and Ethereal Haze are cut since they don't meaningfully answer a deck full of small evasive fliers and counterspells; Fanged Flames, Thraben Charm, and Lightning Bolt are trimmed since their small flying creatures and Faerie Miscreant/Faerie Seer are better answered by cheap blue-hate than by single-target removal that trades down on mana. Keep Skred and Counterspell as the core removal/interaction suite since they scale well against their 1/1s and their spells.