Polluted Cistern // Dim Oubliette
The Room mechanic frames self-mill as a two-stage engine, and the split here is unusually clean about which door does which job. The cheaper front half turns your own graveyard-filling into a drain clock, and it counts card types rather than cards: a self-mill trigger that dumps a creature, an instant, and a land in one motion drains three, not one, which quietly rewards a graveyard deck running a diverse spread over a monotype pile. The back half is the payoff you unlock when you can afford it, converting mill into a battlefield reanimation: three cards down, then a creature comes straight back into play. What makes the design coherent is that the two halves feed each other from the same resource. Milling to fuel the reanimation also triggers the drain on the front door, so a deck built to abuse its own library gets both the life loss and the body off a single act of self-mill. That is the tension self-mill strategies have always wrestled with: the cards you bin are cards you paid for and might have wanted, and this pair pays you back on both the mill and the retrieval. It belongs to black's tradition of treating a filled graveyard as setup rather than a wincon, where the yard is a resource to be spent; the drain-per-type counting is the wrinkle that makes assembling variety a deckbuilding priority rather than an afterthought.
