Mardu Energy floods the board with small creatures and generates value through Guide of Souls, Ocelot Pride tokens, and Goblin Bombardment, so Pyroclasm is your most impactful sideboard card — it cleans up token swarms and hits Ragavan and Guide of Souls before they snowball. End of the Hunt provides clean removal for their larger threats like Sephiroth, Fabled SOLDIER and an unanswered Ajani, Nacatl Pariah. Stubborn Denial is trimmed heavily because their gameplan resolves through the battlefield rather than the stack, and Ferocious is inconsistent when they're applying early pressure before your Shadow grows. The mainboard Consign to Memory comes out as well since there are few high-value spell targets to blank in game 1 configurations. Keep Thoughtseize active to strip Goblin Bombardment or Seasoned Pyromancer, which are their most dangerous engine pieces against your trading strategy.