Dreadhound

Two triggers wired to reinforce each other give this Demon Dog its identity. The enter-the-battlefield mill of three cards can immediately feed the drain, because any creature card among those three fires the second ability and each opponent loses a life. From there, every board wipe, combat trade, and later self-mill keeps the pings landing. The drain clause is broad but has firm edges: it wants a creature actually dying (going to a graveyard from the battlefield) or a creature card crossing from a library into a graveyard. Discarding a creature from hand triggers nothing, countering one on the stack triggers nothing, and shuffle effects do nothing unless they happen to deposit a creature card into a yard. That precision is deliberate: it pays out on the right kind of death, not on graveyard activity in general. One creature dying is a single point; a mutual wipe with both boards stocked becomes a haymaker. What makes the Demon Dog unusual is the repurposing of mill, a mechanic that normally reads as a slow attempt to deck an opponent, into an incremental life-drain engine, with a 6/6 body bolted on so the clock keeps ticking even when nothing is dying. Everything the card wants points the same direction: it feeds a sacrifice-heavy black shell, seeds its own mill to prime the drain, and leans on the demon's size to finish what the pings started.