Quenchable Fire

Burn that bills the opponent twice, with a clause that hands them the choice of which payment to make. The first three damage lands immediately, no questions asked; the second three arrive at the start of your next upkeep unless that player or the targeted planeswalker's controller spends a single blue mana to extinguish it. That payment structure is the whole design idea: a four-mana split of six damage at face, the kind of total red rarely gets to write at sorcery rate, wrapped in an out the defender pays for out of their own pocket. Against a deck with no blue, the second jolt is unanswerable and the spell is a six-damage reach play. Against a blue deck, the is rarely a real cost: the trigger does not check until your next upkeep, so the opponent takes a full turn in between and can simply pay during their own main phase from untapped lands they were going to spend anyway. Anyone sitting on a loose blue source quenches the delayed jolt for almost nothing, leaving an overcosted three-damage sorcery behind. The targeting tells you the job: it can only point at a player or a planeswalker, never a creature, so this was never an answer to the board. It is a closer with a conditional kicker baked into the opponent's mana, best where blue is scarce and life totals are the only resource that counts.