Grave Pact

The original edict engine, and the one that turned aristocrats from a flavor of attrition into a lock. The design move is the trigger condition: it fires on every creature of yours that dies, not on a tap or an upkeep, which means it converts your own creature deaths (the resource a sacrifice deck is already spending freely) into mass edicts pointed at everyone else. Pair it with a free sacrifice outlet and a token engine and the board state stops being a negotiation: you trade one creature you were going to lose anyway for a creature from each opponent, repeatedly, until they have none and you still do. The triple-black cost is no accident; it walls off the splash and demands a heavily black shell that can keep the death triggers flowing. Crucially, the edict is sacrifice, not destroy, so it slips past indestructibility and shroud and asks opponents to give up their best creature only if it is their worst, which it rarely is when you are firing it three times a turn. Wizards has revisited the template since (Butcher of Malakir stapled it to a body, Dictate of Erebos flashed it in at instant speed), but this is the clean enchantment that defined the effect.