Flowstone Hellion

The Tempest block's flowstone creatures all shared one design conceit: a free, repeatable pump that traded toughness for power, and this is the version that leans hardest into the bargain. With a cost of zero per activation, the +1/-1 boost has no ceiling except the creature's own toughness, which means a 3/3 can become a 5/1 in a single attack step or kill itself outright if you overcommit. The body's fragility is the entire balancing act: every point of power you buy comes off a toughness pool that starts at three, so the creature is always a few button-presses from suicide. Haste makes the math matter sooner, letting it attack the turn it lands and convert much of its toughness into damage before the opponent gets a turn to answer. The flowstone mechanic is essentially a manual firebreathing engine stripped of the mana tax, and the price of removing that tax is a creature that volunteers to weaken itself with every pump. It rewards the player who knows exactly how much power a given combat needs and not a point more, because the same button that wins a race can hand you a dead creature.