MAGIC: THE GATHERING
Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: Aetherflux Reservoir deals 50 damage to any target.
Aetherflux Reservoir was the key component of the Blue Steel Storm deck...in Standard! Paired with cards like Foundry Inspector, Paradoxical Outcome, and a bunch of small, cheap artifacts, and you got yourself a stew. The deck, while never quite tier 1, was surprisingly consistent.