This is a damage race where Kessig Flamebreather and Guttersnipe punish us for playing a spell-dense deck, so we need cheap interaction to keep their damage engines off the board. Cast into the Fire kills Voldaren Epicure or a Sneaky Snacker outright and can double up on two small creatures, while End the Festivities wipes their 1-toughness Epicures and Snackers for one mana (it only deals 1 damage, so it whiffs on Guttersnipe and Flamebreather). Pyroblast stays boarded since their only blue card never gets cast off an all-Mountain manabase. We trim slower value cards like Reckless Impulse and Wrenn's Resolve that don't advance our clock fast enough against their burn.

Dimir Control has no red permanents or spells, but it is loaded with blue targets: Counterspell, Dispel, Brainstorm, Lorien Revealed, Spellstutter Sprite, Faerie Seer, Ninja of the Deep Hours and Baleful Strix are all legal Pyroblast targets, letting us blow up a counterspell or kill a card-advantage engine for one mana. We cut our slower card-selection sorceries since they don't help us fight through countermagic and we'd rather hold up cheap interaction to protect our combo turn. Keep the core engine intact — the plan is still to assemble a critical mass of bodies and close with Rally at the Hornburg before they stabilize with Thorn of the Black Rose or grind us out.

Spy Combo's manabase and engine are entirely green and black with no red cards and almost no true artifacts to target with Cast into the Fire or Gorilla Shaman, and Relic of Progenitus does little since their value comes from casting Lead the Stampede and Winding Way off live cards rather than graveyard recursion. Our best angle is simply to be faster than their mana-dork ramp into Generous Ent and Troll of Khazad-dum, so we keep the full aggressive core untouched. There's no clean sideboard card that improves our matchup enough to justify cutting a core piece, so we make no changes and race on the play.