Molten Man, Inferno Incarnate

The printed 0/0 body is a trap and a promise at once: this creature only sticks the landing if you already control at least one Mountain when it resolves. State-based actions check the moment it enters, before the search trigger goes on the stack, so a Mountain-less board watches it die as a 0/0 even as its trigger still resolves to fetch a Mountain. Its static ability, granting +1/+1 for each Mountain you control, is what keeps it alive off your existing lands, and the entering Mountain then compounds that size the instant the trigger resolves. From there the body is a live readout of your red mana: every Mountain you draw or fetch pushes its stats up in real time, not through +1/+1 counters that could be shrunk or removed, but through a count that recalculates with your board. The leave-the-battlefield clause is the tax on all that growth. When it leaves the battlefield, you sacrifice a land, so removal is a clean one-for-one rather than any kind of blowout: the fetched Mountain on the way in and the sacrificed land on the way out cancel to zero card advantage, with the trade playing out entirely as tempo. That symmetry defines it. It belongs to a small line of red beaters whose size is your resource count made flesh, but the death-tax rider means the payoff is conditional on keeping the creature on the battlefield rather than trading it away.