Executioner's Capsule

The clever bit is splitting the cost across two turns. You pay a single black mana to deploy the capsule, and it waits there as a primed, visible answer everyone at the table can read, until you spend the back half to crack it for a kill. That sequencing is what keeps it competitive where a plain destroy-target-nonblack-creature spell would feel overpriced: the removal is already in play before you need it, so the activation lives at instant speed off whatever mana you have open. You bank the commitment early and pay the discount later. The nonblack clause is the obvious tax: it folds in mono-black mirrors and never points at a black threat (yours or anyone's), though nothing stops you from cracking it on your own nonblack creature when a sacrifice or trample-through line calls for it. The artifact body is the genuine liability, since it answers to disenchant effects before it ever resolves a kill. But that same artifact typing is also why it endures: it slots into artifact-matters and graveyard recursion shells that have no use for a buried-treasure instant, and because it is a black permanent, it lines up with the recursion and tutor effects black already reaches for. Its whole proposition is patience: telegraph the threat early in exchange for flexibility on the turn it matters.