Mono-Black Demon Annex

A grindy mono-black midrange deck built around the Unholy Annex // Ritual Chamber value engine, using Demons to draw cards while the Bloodletter of Aclazotz + Unstoppable Slasher combo threatens a one-turn kill.

Unholy Annex // Ritual Chamber rewards you for controlling a Demon by drawing cards at end of turn, and Bloodletter of Aclazotz is itself a Demon that also doubles the life your opponent loses during your turn. The deck's signature line is Unstoppable Slasher connecting in combat: it makes the opponent lose half their life (rounded up), and Bloodletter doubles that loss so a single hit can bring them to zero. Deep-Cavern Bat and cheap removal clear the path while Lord Skitter, Sewer King and Vein Ripper provide resilient bodies, lifegain, and graveyard pressure. Deadly Cover-Up pulls double duty as a sweeper that also strips the opponent's best threat.

Keep hands with at least two to three Swamps plus a real play, ideally a turn-one/two interaction spell (Shoot the Sheriff, Bitter Triumph, Nowhere to Run) and a threat like Deep-Cavern Bat or Unstoppable Slasher. Snap-keep any hand containing Unholy Annex plus a Demon. Mulligan hands that are all lands, all expensive spells, or that lack a source of black mana. Do not keep a one-land hand even with strong cards.

Early game: deploy Deep-Cavern Bat to strip a key card and start chipping in the air, and use cheap removal to stay alive. Mid game: resolve Unholy Annex // Ritual Chamber and establish a Demon so you begin drawing every turn, then use that card advantage to trade efficiently. Late game: close with Bloodletter of Aclazotz plus Unstoppable Slasher for a near-one-shot, or grind them out with Demon tokens from Ritual Chamber and repeated Annex draw; Vein Ripper and Massacre Girl, Known Killer help stabilize against go-wide boards.

Watch out for graveyard hate, which shuts off Unstoppable Slasher recursion and Vein Ripper triggers, and for enchantment removal aimed at Unholy Annex before it pays off. Fast red/aggro starts can race you if you miss early removal, and heavy counterspell decks can answer your key Demons. Because the deck is mono-black and colorless-light on utility, guard your life total carefully and sequence removal so your combo pieces survive.