Firestorm

A single red mana buys a scaling X-spell whose whole cost is paid in cardboard: the mana value never moves off one, but the discard clause is the real meter, tying together two numbers that most burn keeps apart. The cards you throw away set both the damage and the number of targets, and the two scale in lockstep: discard three, and you deal three damage to each of three separate targets. That coupling is what stops the spell from becoming a one-card kill. You cannot dump your hand to bury a single creature, because every card pitched demands another body to point at, so the math always spreads the damage across a board rather than concentrating it on a player. The friction lives in the hand, not the manabase, which inverts the usual cost structure of red removal: the limiter is how much you are willing to empty your grip, not how much mana you can untap into. That makes it a deterrent in most decks and an enabler in the ones built to want a stocked graveyard, where discarding a fistful is fuel for recursion, reanimation, or flashback rather than a pure loss. A burn spell that asks for your cards instead of your mana is a rare design knob, and Firestorm uses it about as cleanly as the era ever managed.