01Cast the spell that costs mana firstFlurry counts your second spell each turn regardless of cost, so the order only matters for what you can still respond to. Spend the mana while you have it.
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02Cast the free spell secondMishra’s Bauble and Mutagenic Growth cost nothing, so they are the cheapest way to reach two spells on a turn you also developed.
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03Take the MonkA 1/1 with prowess, and the Cutter can attach to it for free.
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04Attach and attackEquipped, the Monk has trample and haste, so it attacks the turn it appears.
Rules noteThe second spell is the trigger, and the free spells exist to be it. A turn where you cast one spell is a turn the Cutter did nothing.
Strategic purposeTurn a cantrip into a hasty attacker every turn, so the board rebuilds faster than removal removes it.
Failure conditionsCori-Steel Cutter is an artifact, and Boseiju, Who Endures answers it from a land slot at 25.9% of maindecks. Force of Negation counters it for free at 25.5%, because the free mode is live when it is not the caster’s turn, which is exactly when you cast it.
Tested againstCards the field actually maindecks, played against this line rather than assumed.