Molten-Core Maestro

The reward structure here pulls in two directions at once, and that split is the whole design. The counter accrues on every instant or sorcery, so a spell-dense shell grows the body regardless of how you build; that is the aggressive incentive, a 2/2 with menace that climbs while you cast. But the second clause only fires at five or more mana spent, and it pays you red equal to power, not a flat amount. That coupling is the clever part: the counters that make the creature a clock are the same counters that make each big spell refund more mana, so the ritual half of the card scales off the aggressive half. A Goblin Bard sitting at four power turns a five-mana spell into five red back, since the counter lands first, which is enough to chain into another expensive spell the same turn. The tension the card resolves is the usual problem with mana-positive engines: they want you to durdle, but a durdle plan gives an opponent time to remove a 2/2. Menace and the ever-growing body keep the creature threatening damage while the ritual engine assembles, so you are not choosing between pressuring life totals and generating mana; the design insists you do both, and rewards the deck that can spend the red it produces the same turn it appears.