This is not a mirror: you are the Naya Initiative deck against an Eldrazi list, and the matchup is decided by how Chalice of the Void and Trinisphere sequencing shapes their mana-hungry spells. Keep those mainboard pillars intact and don't touch them. Pyroblast stays in the sideboard because the Eldrazi list has no blue cards, so it would have no legal targets. The extra Eldrazi Confluence is the better include: its modes are flexible, and stacking two +3/-3 modes can kill a Thought-Knot Seer, while the Eldrazi Scion tokens give you extra mana. Chrome Mox costs you a card to imprint, so trim one copy to make room. This is largely a Chalice/Trinisphere and mana-development race, so avoid over-boarding away from your core plan.