Mystical Dispute is excellent here since a big chunk of their deck (Deduce, Prismari Command, Spell Pierce, Spell Snare, Make Disappear) is blue, so it often costs just {U} to make them pay {3}, and it still counters their non-blue cards like Fiery Impulse, Volcanic Spite, Fable of the Mirror-Breaker and Indomitable Creativity unless they pay {3}; Change the Equation covers their cheap interaction (Fiery Impulse, Spell Pierce, Spell Snare, Volcanic Spite) and also counters a red Indomitable Creativity cast with X of 3 or less. Spell Snare is weaker since relatively few of their cards are exactly mana value 2, and Temporary Lockdown mostly only hits the Goblin Shaman token from Fable of the Mirror-Breaker, the Illusion tokens from The Theorist, Jace Beleren, and their Clue and Treasure tokens early, so trim it. Yorion is a 4/5 flyer that their burn (Fiery Impulse, Volcanic Spite, Prismari Command) can't easily kill on its own, giving you a resilient blocker and value creature to grind through their Indomitable Creativity game plan; keep Supreme Verdict in since it answers Atraxa, Grand Unifier and any creatures Indomitable Creativity puts onto the battlefield.