Yawgmoth, Thran Physician

A sacrifice engine and a repeatable removal outlet folded into the same activated ability, priced not in mana but in life and bodies. The pay-life sacrifice ability is the reason to build around him: feed him a creature to shrink an opposing threat and refill the hand at once, so every death both answers a board and pays for the next one. That single line collapses two of black's oldest engine pieces (the sacrifice-for-value loop and the drain-the-board removal spell) into one untapped source with no mana cost, which is what lets him convert a wide board into a lethal wall of shrinking creatures faster than most decks can respond. Proliferate closes the loop, stacking the distributed -1/-1 counters so the removal scales past its per-activation ceiling: a single Yawgmoth turn can erase multiple bodies rather than just picking one apart. Protection from Humans is pure upside on the design, and a pointed one, since he is a Human himself: it walls him off from a broad slice of the game's fair aggression while doing nothing to blunt his own killing. The name reaches back to one of the game's foundational villains, the physician-turned-god whose plots underwrote decades of story, which suits a card that treats your own creatures as ammunition and your life total as a spendable resource.