Lyzolda, the Blood Witch

The sacrifice outlet that asks you to choose your fodder by color, and reads the difference back as two distinct payoffs: a red creature converts into two damage at any target, a black one into a fresh card. That split is the whole design idea. Most repeatable sacrifice engines hand you a single effect and let you feed it anything; here the outlet sorts its inputs, which means an aristocrats deck built around her wants its expendable bodies in both colors and wants tokens that carry the right one. A red token cleaves for reach and removal; a black token loops into cards. The cost of two generic mana per activation is the friction that keeps her from machine-gunning a board in a single turn, so she rewards a wide, patient board rather than an explosive one. The 3/1 body is glass: it attacks once and dies to almost anything, which is fine, because the value lives in the activated ability, not the combat math. She predates most of the named sacrifice payoffs that fill this archetype now, and the color-coded fork remains an unusually elegant solution to a problem later designers mostly answered with two separate cards. Feed her right and she is removal, card advantage, and an inevitability engine in one slot; feed her wrong and she is a fragile body holding two mana hostage.