Affinity is nearly all blue with Metallic Rebuke, Preordain, and Sink into Stupor, so Mystical Dispute costs just {U} against their interaction and card draw. Hurkyl's Recall resets their artifact board (Mox Opal, Urza's Saga Constructs, Kappa Cannoneer support pieces) back to hand, disrupting their mana and tempo. Nature's Claim is tempting against Mox Opal or Urza's Saga but is outclassed by the blanket reset of Hurkyl's Recall, so cut it for this plan. Veil of Summer has some value versus their blue removal/counters but we prioritize the cheaper, more impactful Dispute copies instead.