Magmatic Core

Cumulative upkeep usually functions as a death clock, a tax that grows until the card prices itself out of your hand and gets sacrificed. The clever turn here is that the same age counters draining your mana are also the ammunition: each counter you accumulate is another point of damage doled out at end step, so the cost and the payload escalate in lockstep. That alignment is the engine. You pay an arithmetically rising tab ( per counter, every upkeep) and in exchange the end-step trigger swells from a pinprick into something that can answer a real threat. The damage is divided as you choose among targets rather than dealt to each, which makes this scalable point removal, not a sweeper: a late trigger with several counters can dome one fat blocker or pick off a cluster of small ones, but it cannot mimic a Pyroclasm against a genuinely wide board. The split clause is both the saving grace and the catch, because targets are declared at the end step, after the opponent has already seen the exact size of the number and arranged their attack or defense around it. The cruel arithmetic is that the upkeep balloons faster than a red deck wants to commit: by the time the damage pool is large enough to matter, the per-counter payment is large enough to be ruinous, and the card you built around will eventually starve itself off the table.