This is a mono-black Rat tribal swarm deck built around Marrow-Gnawer. The commander gives every Rat fear and turns a single sacrificed Rat into a wave of tokens equal to the Rat count, so the board grows explosively each time it taps. The rest of the deck feeds that loop: token makers and cheap Rats to sacrifice, death triggers that pay off every sacrifice, and lords and scaling Rats that turn a wide board into lethal evasive attacks. How it wins: It floods the board with Rat tokens through Marrow-Gnawer, pumps them with tribal anthems and Rat-count scaling, and swings with fear and menace for lethal damage or poison, backed by life drain from creature casts, token creation and mass-creature payoffs. Key roles: - Rat swarm generation: steady token producers and cheap Rats keep sacrifice fodder on the table and multiply Marrow-Gnawer's output, while Haunted One gives the commander undying and a power boost to Rats whenever it taps (Lord Skitter, Sewer King, Piper of the Swarm, Pack Rat). - Scaling and anthems: Rats whose power counts other Rats, plus type-sharing and chosen-type pumps, make a huge token board into overwhelming damage, often unblockable through fear and menace (Coat of Arms, Ashcoat of the Shadow Swarm, Rat Colony, Swarm of Rats). - Sacrifice payoffs: each Rat sacrificed or killed punishes opponents through forced edicts, draws cards, or banks mana, so the commander's activation and the sac outlets double as removal and card advantage (Grave Pact, Skullclamp, Species Specialist, Black Market). - Drain and alternate damage: creature casts, token creation and creature counts bleed opponents out, and Karumonix spreads toxic for a poison angle, giving reach when combat stalls (Mirkwood Bats, Gruesome Fate, Karumonix, the Rat King, Valley Rotcaller). - Tribal tutoring and recursion: repeatable Rat searches, cost reducers and graveyard returns keep the creature density high, and Rat Colony multiples can be returned all at once (Ratcatcher, Herald's Horn, Rat King, Verminister, Echoing Return). - Mass black mana: Swamp-count lands with Urborg and Three Tree City produce huge amounts of black mana for Crypt Rats board wipes and big turns (Cabal Coffers, Crypt Rats, Three Tree City).

Marrow-Gnawer decklist

• Arcane Signet
• Bontu's Monument
• Coat of Arms
• Herald's Horn
• Jet Medallion
• Lightning Greaves
• Patchwork Banner
• Skullclamp
• Sol Ring
• Thornbite Staff
• Thrumming Stone
• Vanquisher's Banner
• Bojuka Bog
• Cabal Coffers
• Cabal Stronghold
• Mudflat Village
• 27× Swamp
• Swarmyard
• Three Tree City
• Urborg, Tomb of Yawgmoth
• Ashcoat of the Shadow Swarm
• Ayara, First of Locthwain
• Crypt Rats
• Ink-Eyes, Servant of Oni
• Karumonix, the Rat King
• Lord Skitter, Sewer King
• Mirkwood Bats
• Ogre Slumlord
• Pack Rat
• Persistent Marshstalker
• Piper of the Swarm
• 17× Rat Colony
• Rat King, Verminister
• Ratcatcher
• Species Specialist
• Swarm of Rats
• Tangled Colony
• Typhoid Rats
• Valley Rotcaller
• Black Market
• Grave Pact
• Haunted One
• Phyrexian Arena
• Dark Ritual
• Deadly Dispute
• Defile
• Foul-Tongue Shriek
• Go for the Throat
• Vampiric Tutor
• Village Rites
• Demonic Tutor
• Echoing Return
• Feed the Swarm
• Gruesome Fate
• Swamp
• Swamp
• Swamp