Affinity's list is loaded with free spells — 4 Mox Opal, 4 Mishra's Bauble, 4 Tormod's Crypt, 2 Welding Jar, and Engineered Explosives cast for X=0 — all of which Vexing Bauble counters outright since it triggers on any spell cast with no mana spent; it does not stop Kappa Cannoneer's improvise (which pays generic mana) or Metallic Rebuke (which still costs {U}), but there are plenty of legal targets to make it strong here. Bring in all three sideboard copies alongside the two maindeck copies you already run. Trim the single Emrakul, the Promised End and two Sowing Mycospawn, since this matchup is a race decided by the combo rather than grindy top-end, and Emrakul's high cost is too slow against Affinity's explosive curve.