Flowstone Thopter

The Flowstone mechanic bolted a single tradeoff onto a row of creatures: pay one mana to push power up and toughness down, locking in evasion as a side effect. On a seven-mana 4/4 that math is a hard ceiling. Each activation buys flight and a swing toward more damage, so the body shrinks every time you reach for the air; a 4/4 becomes a 5/3 flyer, then a 6/2, then a 7/1 one ping away from death by any chump trade. The toughness pool is the price that keeps the ability honest: it is repeatable and instant-speed, but the creature folds before you can lean on it too long. What seven mana actually buys is a finisher you can convert from ground beater to evasive threat at the moment the opponent leaves the sky open, committing the toughness for the turn whether or not the alpha strike connects. The rate never justified the cost, and the Flowstone line never produced a constructed staple, but the toughness-as-resource framing is a clean piece of late-block design, the same self-cannibalizing math that makes a creature feel powerful and fragile in the same breath.