Overview:

This mono-black deck revolves around Marrow-Gnawer, leveraging Rat tribal synergies to flood the board with tokens and exploit sacrifice outlets. The primary strategy involves generating exponential Rat tokens via Marrow-Gnawer’s ability, amplified by anthem effects like Coat of Arms and Ashcoat of the Shadow Swarm, while secondary combo lines use Thornbite Staff and Phyrexian Altar for infinite tokens/mana. The deck also incorporates a toxic subtheme with Karumonix, the Rat King and stax elements like Contamination to disrupt opponents. Marrow-Gnawer is critical as the linchpin for token generation and combo potential, though the deck includes redundancy via Rat Colony swarms and recursion tools.

Primer:

Core Strategy Execution:

1. Early Setup (Turns 1-3): Deploy fast mana (Sol Ring, Mana Vault, Grim Monolith) and card advantage engines (Necropotence, Phyrexian Arena). Cast low-cost Rats (Rat Colony) to build early pressure.
2. Mid-Game Engine (Turns 4-6): Cast Marrow-Gnawer, ideally protected by Swarmyard or haste from Sting, the Glinting Dagger. Sacrifice Rats to Marrow-Gnawer to create a critical mass of tokens. Use Skullclamp or Ayara, First of Locthwain to draw cards.
3. Win Conditions (Turns 5+):
   • Combat Overkill: Buff Rats with Eldrazi Monument, Coat of Arms, or Ashcoat of the Shadow Swarm for lethal swings.
   • Infinite Combos:
     • Tokens/Death Triggers: Equip Marrow-Gnawer with Thornbite Staff. Sacrifice a Rat to Marrow-Gnawer, creating X tokens. Thornbite untaps Marrow-Gnawer, allowing infinite activations. Pair with Phyrexian Altar for infinite mana and tokens.
     • Grave Pact Lock: Combine Grave Pact/Dictate of Erebos with token sacrifices to strip opponents’ boards.
   • Toxic Backup: Karumonix, the Rat King gives all Rats toxic 1, enabling poison wins.

Mulligan Priorities:

• Keep hands with 2-3 lands, including utility like Cabal Coffers or Urborg, Tomb of Yawgmoth.
• Prioritize fast mana (Sol Ring, Mana Vault) or early Rats (Rat Colony).
• Include at least one card advantage engine (Necropotence, Phyrexian Arena) or tutor (Demonic Tutor, Imperial Seal).
• Avoid hands lacking ramp or Rat density.

Key Tips:

• Protect Marrow-Gnawer: Use Command Beacon to bypass commander tax and Swarmyard for regeneration.
• Sacrifice Synergies: Phyrexian Altar and Ashnod's Altar turn tokens into mana for explosive turns.
• Leverage Stax: Contamination locks opponents out of non-black mana, while The One Ring provides protection.
• Tutor Efficiently: Fetch combo pieces (Thornbite Staff, Phyrexian Altar) or finishers (Eldrazi Monument) based on the board state.

Weaknesses:

Critical

• Board Wipes: Damnation-style effects reset the board, and the deck lacks mass recursion to recover quickly.
• Commander Reliance: Removing Marrow-Gnawer repeatedly cripples token generation and combo potential.
• Anti-Token Tech: Cursed Totem/Torpor Orb disable Marrow-Gnawer and Rat synergies.

Moderate

• Graveyard Hate: Rest in Peace disrupts recursion from Volrath's Stronghold and Ashcoat of the Shadow Swarm.
• Artifact Removal: Targeting key pieces like Phyrexian Altar or Thornbite Staff slows the deck significantly.

Minor

• Life Loss: Necropotence, Phyrexian Arena, and Bolas's Citadel can drain life rapidly if unchecked.
• Fliers: Limited answers to evasive threats without Eldrazi Monument active.

Most Important Cards:

• Marrow-Gnawer (Token engine/combo piece)
• Phyrexian Altar (Mana generation/combo enabler)
• Thornbite Staff (Infinite untap/combo piece)
• Necropotence (Card advantage)
• Demonic Tutor (Tutor critical pieces)
• Coat of Arms (Anthem finisher)
• Grave Pact (Board control)
• Rat Colony (Primary threat/redundancy)
• Contamination (Stax lock)
• Eldrazi Monument (Protection/evasion)

Attribute Ratings:

Speed: 7/10

• Can threaten infinite tokens or combat kills by turns 5-6 with fast mana and tutors, but relies on resolving Marrow-Gnawer.

Resilience: 5/10

• Vulnerable to board wipes and commander removal, but recursion (Volrath's Stronghold) and protection (Swarmyard) offer partial recovery.

Consistency: 8/10

• High tutor density (8+ tutors), redundant Rats, and potent card draw ensure key pieces are accessible.

Interaction: 6/10

• Efficient removal (Deadly Rollick, Toxic Deluge) and stax (Contamination), but lacks counterspells to protect combos.

Rating Justification:

This deck operates at a 6.5 - 7.0 power level, capable of winning via combat or combo by turns 5-6 with robust tutoring and fast mana. However, its reliance on Marrow-Gnawer and vulnerability to board wipes prevent it from reaching higher tiers. The inclusion of stax elements and efficient combos elevates it above casual builds.

Power level: 6.5 - 7.0