Missing sideboard cards? The full 15-card sideboard runs about $201.
Buy sideboard on ManapoolFatal Push kills Fanatic of Rhonas outright (mana value 2) without needing revolt, and it even handles Slumbering Trudge, since that card's mana value on the battlefield is only 1. Still, it's dead against their true heavy hitters like Ulamog and Emrakul, so it's cut for Toxic Deluge, which sweeps their smaller creatures like Fanatic of Rhonas and Disciple of Freyalise. Consign to Memory counters their colorless spells and creatures (Emrakul, Ulamog) and disrupts Kozilek's Command outright, though it can't touch green spells like Slumbering Trudge or Green Sun's Zenith since those aren't colorless. Pithing Needle can name Green Sun's Zenith-fetched utility creatures' activated abilities or shut down a problematic land like Mosswort Bridge. Basim dies too easily to their bigger creatures in combat and doesn't pressure a deck this grindy, so it's trimmed for interaction.
Their Wrath of the Skies and Avengers Disassembled punish small creatures, so we bring in Kaito, Bane of Nightmares as a more resilient planeswalker-creature threat that survives sweepers when it isn't a creature on their turn. Vexing Bauble punishes their many 0-mana-adjacent plays less, but Pithing Needle can shut down Field of Ruin or Demolition Field to protect our lands, or lock a copy of The Legend of Roku's activated ability. Harbinger of the Seas turns off their Field of Ruin, Demolition Field, and colored lands like Sacred Foundry and Cori Mountain Monastery. Erayo and Basim fold to their removal (Path to Exile, Galvanic Discharge) and sweepers, so they're cut for more durable, disruptive permanents.
Vexing Bauble counters their many 0-mana spells like Mox Opal and Mishra's Bauble outright, disrupting their explosive starts. Consign to Memory counters colorless spells like Engineered Explosives and Mishra's Bauble on the stack, and can also counter relevant triggered abilities in this matchup. Pithing Needle can shut down a repeatable activated ability like Emry, Lurker of the Loch's graveyard-casting activation, denying their artifact recursion engine. Erayo and Basim trade poorly into their efficient artifact creatures and removal (Engineered Explosives), so they make way for more targeted artifact disruption in this mirror-adjacent matchup.