Bottle-Cap Blast

Overkill is usually wasted mana, but here it's the payoff. Five damage rarely lands cleanly on a permanent worth all five points, so the design turns the leftover into fuel: aim the blast at a two-toughness creature and the three excess damage becomes three tapped Treasures. Point it at something too small to justify it, and you invert the ordinary calculus of a big burn spell, where efficient removal means pointing the damage at a target that eats every point. Improvise softens the front-end cost by letting your existing artifacts chip in, and the Treasures it generates feed forward into whatever wants ritual-style mana next, closing a small loop where artifacts pay for the spell and the spell pays back in artifacts. The tension is between using it as clean removal (efficient, no Treasures, and a waste of half the text) and using it as a mana-positive burn spell that happens to kill something on the way. That second mode is the one the design rewards: a five-damage instant that can leave you further ahead on resources than you were before casting it, provided you're willing to fire it at a target the damage will spill past.