Savra, Queen of the Golgari

Two triggers keyed to color, and the asymmetry between them is what makes the card sing in a Golgari sacrifice deck. Sacrifice a black creature and you turn each opponent into the victim of a table-wide edict, paying two life to make everyone shed a body; sacrifice a green creature and you bank two life back. The reason this works as an engine rather than a curiosity is that the best sacrifice fodder is so often both black and green at once, so a single creature fed to an outlet fires both halves: one attrition trigger aimed outward, one life-gain trigger aimed back at the cost. Crucially, neither ability cares about death in general: milling, discarding, or a sweeper destroying your board does nothing here. The trigger is the sacrifice action itself, which is why the engine wants dedicated outlets that let you fling fodder on demand. That dual-color overlap is the hook, the thing that separates this from a Diabolic Edict stapled to a 2/2 body. The body itself does little; the value lives in chaining the triggers off a recursion engine, where every loop of a self-sacrificing creature is another edict prepaid against the whole table. None of it comes free, which is the restraint that keeps the card fair: opponents choose what they give up, so the black trigger grinds boards down rather than sniping the threat you want gone, and the life cost is a genuine resource against a fast clock.