Dragon's Fire

Two spells hide inside one instant, and the additional cost decides which you get. Cast it with an empty hand and no Dragons on board and you have a strictly worse burn spell, a two-mana instant that answers small threats and stalls out against anything bigger. Reveal a Dragon from hand or point at one you already control and the number scales to that creature's power, which in a deck built to field them turns a modest removal spell into an assassination tool that clears almost anything walking the ground. What makes the enabler nearly free is that it asks for nothing you were not already doing: a Dragon deck is holding or playing Dragons regardless, so the reveal is card information at worst and a kill at best. The design belongs to a long line of removal that pays off a tribal commitment, but it is stingier than most of them, refusing to reward you for merely wanting Dragons. You have to actually have one, in hand or on the battlefield, in the moment you cast. That gate is what keeps the floor honest: the payoff is enormous, so the cost of accessing it is that you built the deck to earn it.