Sivriss, Nightmare Speaker

The engine hidden inside this Snake Cleric is a symmetrical hostage negotiation, but the hostage is your own graveyard. Sacrifice another creature or an artifact, mill yourself one card for each opponent, then return each of those milled cards to your hand unless the corresponding opponent pays three life to keep it buried. It reads like self-mill, but the strategic axis is the tax: every activation asks a table of opponents to individually decide whether stopping your card advantage is worth three life, and against multiple opponents that arithmetic compounds. The elegance is in the resource conversion: Sivriss turns two of black's cheapest inputs (expendable bodies and disposable artifacts) into repeatable card refill plus a slow group-slug drain, all fueled by your own library rather than a draw step. Pair it with tokens, Treasure, or an aristocrats shell and the sacrifice cost becomes free upkeep for a grind engine that also fills your graveyard toward whatever payoffs you have loaded. The Background slot then dictates the archetype: the same 3/3 can anchor a sacrifice-value build, a life-loss plan, or an artifact-loop line depending on which second commander you pin to it. Its ceiling is set less by its own numbers than by how reliably you can feed the tap ability and how much your opponents value keeping those milled cards out of your hand.