Blood Moon is strong in this matchup, so it stays in: their Eldrazi Temple, Ugin's Labyrinth, Urza's Saga, Boseiju, Shifting Woodland and Gemstone Caverns are all nonbasic and become Mountains, which cuts off most of the {C} they need for Kozilek's Command, Devourer of Destiny and Sowing Mycospawn's kicker (only their 6 Forests are unaffected). Cut Goblin Bombardment, which is too slow against their big creatures and mana ramp. Wear/Tear gives us answers to artifacts like Blade of the Bloodchief, Haywire Mite and Urza's Saga's Construct tokens, and the Tear half can destroy Urza's Saga itself since it is an enchantment. Damping Sphere slows their Eldrazi Temple/Ugin's Labyrinth ramp, because lands tapped for two or more mana produce only {C}, and it taxes their multi-spell turns. Vexing Bauble and Celestial Purge stay in the sideboard: they have no zero-mana spells for Bauble to counter, and their deck has no black or red permanents for Purge to exile. Focus on racing with Ragavan and Ocelot Pride, and don't count on instant-speed removal like Galvanic Discharge for Emrakul, which has protection from instants; pressure them before they assemble their ramp into a game-ending threat.

This combo deck wins through Blade of the Bloodchief plus Basking Broodscale looping Eldrazi Spawn tokens, so artifact and token disruption is key. Vexing Bauble counters their many free-cost activations is not relevant to this combo loop specifically since those are activated abilities, but it does stop zero-mana spells like Ancient Stirrings is wrong (that costs {G}); its real value here is disrupting their one-mana artifact answers and taxing their deck generally, so treat it as a mild value include rather than a silver bullet. Surgical Extraction can strip Blade of the Bloodchief from their deck entirely once you see a copy, which is the single most impactful disruption against the loop. Damping Sphere slows Eldrazi Temple and Ugin's Labyrinth ramp, buying time. Goblin Bombardment and Thraben Charm are cut since they don't interact meaningfully with the combo itself; prioritize fast clock pressure and removal on Basking Broodscale before the loop turns on.

Blood Moon is weak here since Izzet Prowess runs mostly basics and fetches that can grab basic Mountains, so cut both copies. High Noon is excellent, restricting them to one spell per turn, which cripples their low-to-the-ground, multi-spell-per-turn plan built around Expressive Iteration and cheap cantrips. Surgical Extraction can strip a key cheap spell like Lightning Bolt or Monastery Swiftspear after it resolves once, disrupting their curve. Static Prison comes out since their threats are mostly small, cheap creatures that are easy to race rather than needing a one-for-one exile effect; prioritize applying pressure with Ragavan, Guide of Souls, and Ocelot Pride while using Galvanic Discharge to stay ahead on board.