Brimstone Roundup

The second-spell trigger is the axis here, and it borrows from a lineage of "cast your second spell" payoffs that ask you to sequence your turn deliberately rather than dump your hand. What separates this one from a simple prowess-style bonus is that the payoff is a permanent, not a one-turn buff: each qualifying turn banks a body onto the battlefield, and those bodies compound. The Mercenary tokens themselves are deliberately weak in isolation (a 1/1 whose tap ability is sorcery-restricted and only pumps a single point of power), which is the pressure valve that keeps the engine from snowballing at instant speed. The design intent shows in how the two halves talk to each other: plot lets you set the enchantment aside on an earlier turn and land it for free later, meaning the turn it resolves is not the turn you have to also cast two spells to profit. You spend the mana up front, then arrive already open to build the board. That timing wrinkle matters because it decouples the setup cost from the payoff turn, letting an aggressive deck front-load its investment when it has the mana and reserve its actual spells for when the enchantment is online. It rewards a low-curve, high-density shell that can reliably chain two casts a turn, and punishes nothing so much as a stalled hand.