Magma Mine

A storage device built entirely around patience, and a study in how slowly mana converts to damage when the rate is genuinely free of upfront commitment. Four mana buys exactly one counter, one point of stored damage, and nothing about the charging ability restricts when you do it: counters can go on at instant speed, during an opponent's end step or in response to a spell, as freely as on your own turn. That flexibility cuts both ways, because the sacrifice is also instant-speed, so the card builds at whatever pace your idle mana allows and fires whenever the table least wants it. The economics never quite work for the impatient (four mana per point is a brutal exchange rate compared to almost any burn spell), so it only makes sense as a long-game inevitability engine: a way to convert surplus mana across a stalled board into a delayed finisher an opponent has to play around for several turns before it releases. It sits in the family of slow artifact mana-sinks that defined a stretch of mid-90s design, where the answer to "what do I do with extra mana" was an artifact that hoarded value one increment at a time. The pressure counters are the whole identity: a literal gauge that ticks up while everyone watches, then unloads in a single shot at the target of your choosing.