Missing sideboard cards? The full 15-card sideboard runs about $177.
Buy sideboard on ManapoolChalice of the Void is awkward here since it hits our own Ancient Tomb-fueled artifacts as much as theirs, and their curve of Thoughtseize/Brainstorm/Ponder at one mana means a Chalice for zero is symmetric at best. Consign to Memory counters their free spells (Force of Will, Daze) for one mana and stops flipped Tamiyo's abilities and Murktide Regent's delve-fueled casting cost issues indirectly by tempo, while extra Force of Negation protects our own threats and answers their Murktide or Kaito. Tormod's Crypt strips Murktide Regent's delve fuel and Nethergoyf/Barrowgoyf-style graveyard value, crippling their best late-game threat. Sink into Stupor comes out since bouncing their cheap Tamiyo or Kaito is low-impact against a deck that can just replay it, and Chalice trims because our own affinity shell is faster and more mana-hungry than the effect is worth against their low curve.
Ocelot Pride Midrange goes wide with cheap creatures (Ocelot Pride, Guide of Souls, Amped Raptor tokens) that Dismember cleanly answers at -5/-5, killing anything they're likely to play outside Voice of Victory's token shell. Pithing Needle can shut down Ocelot Pride's end-step token trigger is actually a triggered ability not activated, so Needle won't stop it directly, but it is excellent against Wasteland, Karakas returning legendary creatures, or a resolved Ajani, Nacatl Pariah's activated loyalty abilities; bring it in mainly for Wasteland/Karakas disruption. Haywire Mite answers their Static Prison or Goblin Bombardment (noncreature artifacts/enchantments) if needed, though it requires green mana we don't have, so treat it as a marginal add only if testing shows a specific need — otherwise favor Dismember count. Chalice of the Void is weak since their curve is spread from one to four mana with key one-drops like Guide of Souls and Ocelot Pride, making a low Chalice symmetric against our own Ancient Tomb-fueled artifacts, so it comes out; Krang trims slightly since it's clunky against Swords to Plowshares and Wasteland-heavy disruption.
Izzet Affinity relies on fast artifact acceleration and key noncreature spells like Force of Will and Sewer-veillance Cam, so Force of Negation is crucial to answer their key noncreature spells for free on their turn. Tormod's Crypt is a sideline tool here but still useful against their graveyard-based recursion from Emry, Lurker of the Loch and Goblin Welder. While Hydroblast has legal targets against their red cards like Pinnacle Emissary, Goblin Welder, and Twinshot Sniper, Dismember is preferred because it also handles their blue threats like Emry and Loki, God of Mischief. Chalice of the Void set at one hits their 1-mana spells like Sewer-veillance Cam and Goblin Welder, but it does not counter higher mana value cards like Pinnacle Emissary, Kappa Cannoneer, or Force of Will, so we trim it in favor of more targeted answers. Sink into Stupor is also cut to make room for lower-cost interaction. In its place, Dismember gives us cheap, efficient removal for key creatures such as Emry, Pinnacle Emissary, Goblin Welder, and Loki, God of Mischief. Overall plan: bring in Tormod's Crypt, Force of Negation, and Dismember, trimming Chalice of the Void and Sink into Stupor for a leaner, more resilient plan against their countermagic and artifact threats.