Necropolis Fiend

The 4/5 flying body carries a nine-mana price tag that almost nobody pays in full: fill the graveyard, exile it card by card, and the flyer lands for a fraction of the printed cost. What separates this Demon from other delve creatures is that the graveyard keeps working after it resolves. The same yard that cheated it onto the battlefield feeds an activated ability that shrinks a creature by X/X for X, a tap, and X more cards exiled. That shared resource is the design's real tension. Cards you spend to cheat out the body are cards no longer available to power the removal engine, so a fast cast leaves a thin yard to draw from later, and the on each activation means even a stocked graveyard never makes the removal free. Flying gives the body evasion that a single -X/-X activation on a blocker can widen, and a deep graveyard turns the ability into repeatable point removal that scales with how long the game runs. The card wants a deck that refills the yard faster than it spends it, a harder balancing act than the casting discount suggests, and the reason this Demon plays as a grindy control finisher rather than a cheap beater: every point of value it extracts, on the way in and every turn after, comes out of the same shrinking pile.