Bloodletter of Aclazotz doubles the life opponents would lose during your turn. Unlike a damage-only multiplier, it applies to life loss from drain effects as well as combat and burn. This makes the Vampire Demon a strong payoff for black decks that can produce several life-loss events or one large event before passing the turn.
Gray Merchant of Asphodel is a natural partner because its entry ability drains each opponent, and Bloodletter's three black mana symbols also contribute to devotion. Exsanguinate and Torment of Hailfire provide other ways to turn a large mana supply into increased pressure. The effect does not increase life loss during opponents' turns, so timing is a central part of evaluating a potential pairing.
Rush of Dread offers a direct finishing interaction against one opponent when cast during your turn with its half-life mode. The targeted opponent would lose half their life rounded up, and Bloodletter doubles that loss. Assuming no other relevant effects interfere, the resulting loss is enough to remove that opponent's remaining life total. The setup still needs both cards and the mana for the chosen mode.
The triple-black requirement makes the card most comfortable in black-heavy mana bases. It has flying, but its main role is amplifying other effects rather than winning through its own attacks. Plan a follow-up that uses the ability promptly, since passing the turn gives opponents a window before the multiplier becomes relevant again.
