Overview:

This mono-black Rat tribal deck helmed by Karumonix, the Rat King focuses on poison proliferation through Toxic and Infect mechanics, amplified by massive Rat swarms. The strategy leverages 18 copies of Relentless Rats paired with tribal synergies like Thrumming Stone for explosive board development, while Marrow-Gnawer + Thornbite Staff enables infinite Rat generation. Karumonix serves as both a card advantage engine (digging 5 cards deep for Rats on ETB) and a Toxic enabler, turning every Rat into a poison threat. Secondary win conditions include Bolas's Citadel life-pay synergies and Phyresis Outbreak leveraging accumulated poison counters.

Primer:

Core Strategy Execution:

1. Early Setup (T1-3): Deploy mana accelerants (Sol Ring, Crypt Ghast, Jet Medallion) and key tribal artifacts (Herald's Horn, Door of Destinies). Use Vampiric Tutor/Imperial Seal to find Thrumming Stone or critical Rats.
2. Board Flood (T3-5): Cast Relentless Rats with Thrumming Stone triggers, creating a critical mass of 4/4+ Rats. Deploy lords like Ashcoat of the Shadow Swarm and Bad Moon to amplify power. Use Plague of Vermin for instant swarms.
3. Poison Delivery (T4-7): Attack with Toxic Rats (all granted Toxic 1 via Karumonix) to spread poison counters. Use Ichor Rats for global poison seeding and Karn's Bastion/Vraska's Fall for proliferation. Activate Marrow-Gnawer + Thornbite Staff for infinite Rats if needed.
4. Finishers: Phyresis Outbreak as a poison-based board wipe, Bolas's Citadel for life-pay storm turns, or Kindred Dominance clearing the path for lethal combat.

Mulligan Priorities:

• Keep hands with 2-3 lands including Swamps for Cabal Coffers/Nykthos.
• Prioritize early plays: Relentless Rats + Thrumming Stone, Karumonix, or mana accelerants.
• Avoid hands without Rat density or excessive high-CMC cards like Sheoldred.

Key Tips:

• Use Swarmyard to protect key Rats from removal.
• Phyrexian Reclamation ensures Rat recursion against board wipes.
• Filth + Urborg, Tomb of Yawgmoth grants unblockable swarms.
• Ad Nauseam can draw 15+ cards due to low average CMC (18x 2-drop Rats).

Weaknesses:

Critical

• Extreme vulnerability to Rest in Peace/Leyline of the Void (shuts off Thrumming Stone, Relentless Rats scaling, and recursion).
• No inherent protection against Toxic Deluge/Damnation beyond limited recursion.

Moderate

• Cursed Totem nullifies Marrow-Gnawer/Ashcoat activations and Thornbite combos.
• Struggles against flyers/evasion without Filth active.

Minor

• Drannith Magistrate blocks Karumonix's ETB.
• Life loss from Bolas's Citadel/Ad Nauseam can become dangerous.

Most Important Cards:

• Thrumming Stone (Relentless Rats enabler)
• Marrow-Gnawer (Token generator + combo piece)
• Relentless Rats (Primary threat)
• Ashcoat of the Shadow Swarm (Lord effect + recursion)
• Bolas's Citadel (Alternative wincon)
• Karumonix, the Rat King (Toxic enabler + card advantage)
• Cabal Coffers (Mana scaling)
• Phyresis Outbreak (Poison finisher)
• Demonic Tutor (Consistency)
• Thornbite Staff (Infinite combo enabler)

Attribute Ratings:

Speed: 6/10
Can threaten poison wins by T5-6 via Thrumming Stone cascades or Marrow-Gnawer combos, but lacks fast mana beyond Dark Ritual.

Resilience: 5/10
Limited interaction/protection outside Imp's Mischief and graveyard recursion. Relies heavily on board presence.

Consistency: 8/10
18x Relentless Rats + 7 tutors + Thrumming Stone ensure reliable Rat access. Karumonix provides card advantage.

Interaction: 4/10
Focused on creature removal (Go for the Throat, Infernal Grasp) but lacks stack interaction beyond Withering Boon.

Rating Justification:

This deck demonstrates focused tribal synergy with T6-7 win potential through poison or infinite Rats, but its linear strategy and vulnerability to common graveyard/artifact hate prevent higher optimization. The strong consistency and combo finish elevate it above casual tiers.

Power level: 5.5 - 6.0