Missing sideboard cards? The full 15-card sideboard runs about $346.
Buy sideboard on ManapoolNull Rod shuts off their Mishra's Bauble, since its ability is an activated ability of an artifact. It also shuts off our own Lotus Petals, because Petal's mana ability is an activated artifact ability and Null Rod has no exception for mana abilities. That is a real cost, so we trim Lotus Petal to make room for the disruption package. Any Petals left in the deck are blanked while Null Rod is out, so we accept that. Thorn of Amethyst taxes their noncreature spells, including Brainstorm, Ponder, Thoughtseize, Daze and Fatal Push, and it stacks with Chalice of the Void to make their mana awkward. Thorn also taxes our own noncreature spells, such as Chalice, Kozilek's Command and Eldrazi Confluence, so we lean on our creature-heavy plan against a deck that is trying to grind. Eldrazi Linebreaker is the weakest body here. It is a colorless 3/3, so Snuff Out can target it and Fatal Push can kill it once revolt is on, which their fetchlands turn on easily. A couple come out for the disruption package.
Dismember is premium removal here, cheaply killing Ocelot Pride, Guide of Souls, Ajani's Cat Warrior tokens, or Amped Raptor before they generate value, and the life payment is manageable since this matchup isn't about racing damage as much as board control. The extra Eldrazi Confluence gives us a flexible answer that can shrink multiple small Cats with its +3/-3 mode while also exiling and resetting a problematic permanent like Ajani, Nacatl Pariah. Sire of Seven Deaths is too slow and clunky against a deck that goes wide with cheap threats and has Swords to Plowshares to answer our one big body, so we trim it for more efficient interaction. A couple Eldrazi Linebreakers come out since their buff doesn't matter if our board gets picked apart by Swords and Static Prison before combat.
Null Rod shuts off their Lotus Petals, one of their few ways to accelerate into Show and Tell or Aluren. It does nothing to City of Traitors or Ancient Tomb, since those are lands, not artifacts. It is a narrow card here. It also turns off our own remaining two Lotus Petals, but Chalice of the Void is unaffected because its counter effect is a triggered ability, not an activated one. Thorn of Amethyst taxes their noncreature spells, including Brainstorm, Ponder, Stock Up, Veil of Summer, Aluren and Show and Tell. It stacks with Chalice of the Void at various counts to hamper their ability to assemble Aluren or Show and Tell into Atraxa on curve. Thorn does not tax creature spells like Atraxa or Acererak, and it also makes our own noncreature spells cost more. We bring these disruptive artifacts in over two Lotus Petals and a couple of Eldrazi Linebreakers, since this matchup is about denying their engine rather than racing and we want the taxing effects online early.