Gibbering Barricade

A blocking body with a repeatable outlet stapled to it: the four toughness holds the ground against early aggression while the sacrifice ability turns whatever else has stopped mattering into a card and a life point. That combination is the reason a defensive creature earns a slot it would not otherwise get. A pure wall trades once and then sits there; this one keeps working after the board stalls, chewing through tokens, spent attackers, or a dying creature's last bit of value on its way to a fresh card. The three-mana activation cost is the brake, and it is a real one: you are paying nearly the wall's own cost each time you fire it, so it is a slow drip rather than an engine, and it competes with everything else you want to do on a given turn. What it wants around it is a supply of creatures worth losing, whether that is disposable chaff, aristocrat-style death triggers, or bodies about to be removed anyway. The design sits in a familiar black tradition of turning attrition into cards, but it does the work from behind a defender's body rather than from a dedicated engine slot, which is a quieter and more forgiving place for that effect to live.