Mardu Energy comes out fast with Ragavan, Guide of Souls, and Ocelot Pride, so Pyroclasm is the key sideboard card — it clears their early board in one shot and invalidates much of their damage plan. Post-board they bring in Thoughtseize and Nihil Spellbomb to attack our graveyard synergies; Consign to Memory can counter the Spellbomb's triggered ability to protect a key Persist or Unearth target. Molten Collapse is flexible removal that can cleanly answer a Ragavan or Goblin Bombardment, the latter being particularly dangerous since it lets them sacrifice creatures in response to our removal. Spell Pierce is at its weakest here since most of their threats are creatures and they're the beatdown player, so we cut it along with the more situational one-ofs. Our core plan of landing Archon of Cruelty or Abhorrent Oculus goes well over the top of anything they can present, so protect the graveyard and stabilize early.