Loathsome Curator

Exploit turns a sacrifice into a payment, and this design spends that payment on a targeted kill: destroy a creature you don't control with mana value three or less. Black already trades cheaply in this kind of removal, so the interesting part isn't the effect but the wrapper. The sacrifice is the cost, the destroy is the reward, and the mana-value cap is what keeps the exchange in check; it will not touch the fatties, but it clears mana dorks, hatebears, small utility creatures, and the two- and three-drops that fair decks live on. What makes the card cohere is that both halves feed the same graveyard-value plan you were already building: the creature you sacrifice is rarely wasted (a token, a spent dork, something with a death trigger of its own), and the gorgon body it leaves behind is a 5/4 with menace, hard to chump and hard to gang-block. The tidy read is a removal spell stapled to a threat, but the more precise one is that it is a value converter, laundering board presence you no longer need into a dead enemy blocker and a swinging clock in a single trigger. Because exploit is optional, an empty board is no dead draw: with nothing worth sacrificing it is still a 5/4 menace that keeps its distance, so the card never rots in hand the way sacrifice-locked designs sometimes do.