Mono Black Attrition

A mono black midrange-control deck that strips the opponent's hand and graveyard, answers every threat with efficient removal, and eventually buries the opponent under Rune-Scarred Demon, Massacre Wurm, and Valgavoth, Terror Eater.

Deep-Cavern Bat and Greedy Freebooter give you a cheap body plus value: the Bat rips a key nonland card out of the opponent's hand, and the Freebooter leaves behind an artifact when it dies. That leftover artifact or the Bat itself fuels Fanatical Offering, which sacrifices it to draw two cards and make a Map token, so your early creatures turn into midgame card advantage instead of sitting around as 1/1s. Greedy Freebooter's token and the Map tokens also ramp you toward your expensive Demons, letting you land Valgavoth, Terror Eater and Rune-Scarred Demon a turn earlier. Rune-Scarred Demon tutors for whichever finisher or answer you need, while Phyrexian Arena keeps the cards flowing so you never run out of removal. Malicious Eclipse and Blasphemous Edict reset go-wide boards, and the flexible removal suite covers everything else: Long Goodbye, Shoot the Sheriff, Nowhere to Run, and Bitter Triumph each catch different permanents, and Gonti, Night Minister turns the opponent's own best cards against them.

Keep any hand with two to four Swamps plus at least one cheap interaction spell (Bitter Triumph, Shoot the Sheriff, Nowhere to Run) or a one-drop like Deep-Cavern Bat or Greedy Freebooter. A hand with Phyrexian Arena and a couple of removal spells is an excellent keep. Mulligan hands with fewer than two lands, no play before turn three, or multiple copies of Rune-Scarred Demon and Massacre Wurm with no way to reach five mana.

Early: Deploy Deep-Cavern Bat or Greedy Freebooter and use Bitter Triumph, Shoot the Sheriff, Long Goodbye, and Nowhere to Run to trade one-for-one with the opponent's early threats. Mid: Resolve Phyrexian Arena or Fanatical Offering to pull ahead on cards, stabilize with Malicious Eclipse against small creatures, and start pressuring with Abyssal Harvester and Gonti, Night Minister. Late: Cast Massacre Wurm to wipe out a board and drain the opponent, then finish with Rune-Scarred Demon (tutoring for the last piece you need) and Valgavoth, Terror Eater. With Phyrexian Arena and Fanatical Offering refilling your hand, you should win any long game.

The deck is slow to close and can be punished by fast aggro if it stumbles on early removal. It has very few ways to interact with opposing enchantments or planeswalkers that dodge your creature removal, and graveyard hate or exile effects can answer your recursive threats. Counterspells hurt because your best cards cost five or more, and drawing multiple expensive Demons without Phyrexian Arena can leave you with a clunky, uncastable hand.