Unholy Heat is efficient removal against Basking Broodscale and Glaring Fleshraker, dealing with their colorless creature engine before it snowballs Eldrazi Spawn tokens. Meltdown can blow up their artifacts at low X, though note it won't hit Devourer of Destiny since that's a creature, not an artifact; still, Meltdown is best used on Vexing Bauble or Blade of the Bloodchief. Combat tricks are weak here since their creatures often have high toughness (Devourer of Destiny is 6/6, Emrakul 13/13), so trading Mutagenic Growth and Violent Urge for real removal and disruption is correct. This matchup is a race where you need to close fast before they assemble their ramp into giant threats.

This is the mirror, so cheap efficient interaction is king. Unholy Heat kills their Dragon's Rage Channeler, Monastery Swiftspear, and Slickshot Show-Off for one mana, scaling to 6 damage with delirium. Spell Pierce protects your key spells or stops their Expressive Iteration/Cori-Steel Cutter on the play. Mutagenic Growth and Violent Urge are combat tricks that don't help you win a race decided by removal efficiency and card quality, so they come out. Keep Lava Dart and Mishra's Bauble as they're excellent in every mirror.

Their deck is full of small, high-value creatures like Orcish Bowmasters, Phelia, and Flickerwisp that Unholy Heat cleanly answers, and delirium makes it a 6-damage answer to Overlord of the Balemurk or Emperor of Bones later in the game. Consign to Memory stops key triggered abilities such as Solitude's ETB exile trigger or Phelia's attack trigger, giving you a way to protect your board or blank their value engines. Mutagenic Growth and Violent Urge are cut because their deck has efficient removal (Fatal Push, Solitude) that punishes overcommitting to combat tricks over card advantage and interaction.