Spell Snare is weak here: it only hits mana value 2 spells like Badgermole Cub and Go for the Throat, and it can't touch Abrupt Decay, which can't be countered. Cut both copies for proactive threats and disruption. Kalitas, Traitor of Ghet is excellent against their Sheoldred, the Apocalypse and Graveyard Trespasser plan, exiling their creatures and gaining lifelink damage race equity. Go Blank makes them discard two cards from a hand full of removal and planeswalkers, then exiles their graveyard, which also blunts Takenuma, Abandoned Mire and Graveyard Trespasser. Keep Thoughtseize and Fatal Push in to fight their proactive hand disruption and removal suite.

Izzet Cauldron is a low-curve tempo-draw deck with small creatures, so Deadly Cover-Up and Languish are mediocre since their creatures like Eddymurk Crab and Hearth Elemental dodge or outscale a -4/-4 sweep, and Sheoldred's Edict gives them a choice of what to sacrifice. Change the Equation answers their cheap cantrips and burn, while Annul is a clean answer to Prismari Charm... but Prismari Charm is an instant, not an artifact or enchantment, so Annul actually whiffs on their whole deck and should stay in the sideboard; replace that plan with more interaction instead. Stormwing Entity is a strong flying body that blocks well and grows off our own spells. Keep Thoughtseize and Fatal Push as premium disruption against their proactive game plan.

UBR is a spells-heavy control/combo deck full of blue cards (Deduce, Make Disappear, Negate) making Mystical Dispute a cheap, efficient counter almost every game. Sheoldred's Edict is weak here since they run very few relevant creatures to force a sacrifice on, so it comes out for more counterspells. Negate covers their Indomitable Creativity and other noncreature threats like Fires of Victory. Keep Dig Through Time and Theorix Charm as premium value and interaction against their grindy card-advantage plan.