Morinfen

For five mana you get a 5/4 flier with no entry tax and no fragile body, which for its era reads as a flat steal until the meter starts running. Cumulative upkeep is the self-correcting bill: one life the first turn, two the second, three the third, the arithmetic compounding until the creature sacrifices itself or drains you faster than it closes. That structure is what lets the rate exist at all. Most fatties of the period paid up front, with a steeper cost or a body that folded to a single removal spell; this one front-loads the threat and back-loads the payment, billing you on installment for power you already have on the board. The strategic read is tempo, not value: a closer you deploy when the game is nearly over, not a permanent you settle in behind. Paying in life rather than mana sharpens the bargain, since black has always spent life like a currency, which puts the clock partly in your hands and partly in your opponent's to outlast. The legendary tag and Phyrexian Horror typing slot it among the Weatherlight saga's named threats, but the mechanical identity is older than the story: it is the classic black trade rendered as a creature, power now and a price that only worsens the longer you let it tick.