Izzet Cauldron is nearly all blue and red noncreature spells, so Mystical Dispute is extremely efficient here at just {U}. Their Agatha's Soul Cauldron plan and Vivi Ornitier want a long game, so extra Beza, the Bounding Spring copies add life gain and card advantage to grind them out. Spell Snare has few clean two-drop targets and Temporary Lockdown whiffs on most of their permanents, so both come out. Keep Supreme Verdict and Dovin's Veto as key answers to their engine pieces.