Hydroblast is excellent here, cheaply countering or destroying red spells and permanents like Kessig Flamebreather, Guttersnipe, and Fiery Temper before the madness engine gets going. Arms of Hadar sweeps away their x/1 and x/3 creatures (Voldaren Epicure, Kessig Flamebreather, Guttersnipe) for -2/-2. Giant's Boulder is too slow against a deck trying to kill you fast, and Extract a Confession is a clunky answer when Hydroblast handles their key threats more efficiently. Keep Dispel and Counterspell in to protect your life total from Fiery Temper and Fireblast.

Dimir Control runs no red spells or permanents, so Hydroblast and Blue Elemental Blast stay in the sideboard. Steel Sabotage comes in to bounce or counter their Baleful Strix, Spellstutter Sprite, Mukotai Ambusher, or Gurmag Angler, giving you tempo and card economy against their own efficient artifact creatures. Arms of Hadar sweeps their small Faerie Seer, Spellstutter Sprite, Augur of Bolas, and Ninja of the Deep Hours tokens/bodies for a one-sided blowout. Giant's Boulder is too slow and low-impact against a deck full of cheap interaction and card selection, and Union of the Third Path is too passive when you need proactive answers to their evasive threats. Keep the counterspell and card draw core intact since those plans are still strong in this control mirror.

Affinity floods the board with artifact creatures and relies on cheap artifact synergy; Steel Sabotage can counter key artifact spells like Thoughtcast, Cryogen Relic, or Utrom Monitor before they resolve, or bounce an already-placed threat to reset their tempo. Giant's Boulder is too slow and doesn't interact with their fast artifact plan. Keep Dispatch at full count since its metalcraft exile mode is excellent against their artifact creatures, and hold Baleful Strix and Refurbished Familiar as efficient blockers against their small flyers like Kor Skyfisher and Glint Hawk.