Crypt Ghast

Mana doubling stapled to a body, attached to a lineage of mono-black scaling that runs back to Cabal Coffers. Where Coffers asks for a dedicated land slot and a tax to activate, this folds the same compounding into a creature that taps no resource of its own: every Swamp you already tap for simply yields two, no fee, no activation. That changes the math of a mono-black deck more than a 2/2 has any right to, because the doubling rides on the basic count you were going to run anyway rather than competing with it. What it pays for the privilege is fragility: a four-mana enchantment-on-legs that any removal spell switches off, and the ramp evaporates the instant the body dies. Extort is the half people undersell. Each spell becomes a one-mana drain, and a deck swimming in doubled black mana is precisely the deck that can afford to pay the again and again across a turn, draining an opponent a point at a time while it fills its own life total. The two abilities work the same problem from opposite ends: the Swamp trigger manufactures a surplus, and extort hands you a place to spend it that bleeds the table out slowly. A ramp engine that doubles as a clock, which is a rarer pairing than the rate suggests.