Elegy Acolyte

Two mechanics that both key off attrition, stapled to a body that fuels one of them itself. The card-draw trigger fires when your creatures connect, so a 4/4 lifelink attacker is already priced to pay its own upkeep: swing, draw, gain, repeat, with the one life you lose immediately refunded by the lifelink damage. That symmetry is the quiet cleverness of the design, because the loss clause exists mostly to keep the draw honest against a naked comparison to older black card-advantage engines, and this body was built to erase it in the same combat step. The Void end-step trigger runs on a different axis entirely: it wants the turn to have been eventful, rewarding you for a nonland permanent leaving play or a warped spell with a 2/2 Robot that, conveniently, is another attacker feeding the combat-damage draw next turn. So the two abilities loop into each other without requiring you to build a dedicated sacrifice shell: the Robots you make on end step become the creatures that trigger the draw, and the removal and trades that naturally happen in a grinding black deck become the fuel for the tokens. It is an engine that assumes attrition is happening around it and simply collects rent on both ends of the exchange, without asking you to manufacture the churn yourself.