Deck Name: Swarm of Vermin
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Format: Legacy
Deck Type: Tribal Combo-Aggro
Colors: Black (Mono-Black)
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Description

Swarm of Vermin is a Legacy tribal combo-aggro deck that unleashes an overwhelming horde of identical creatures to crush opponents under sheer numbers and poison counters. Built around Relentless Rats, the deck takes advantage of their stacking power boost and enables explosive combos with Thrumming Stone, supported by Karumonix, the Rat King, who grants toxic 1 to all Rats for a surprise infect victory.

With ramp tools, board wipes, and recursion, the deck scales incredibly well into the mid and late game, capable of recovering after resets or storming the board with a single spell. Whether facing multiple opponents or grinding out a 1v1 match, Swarm of Vermin turns plague into power.
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How to Play

Early Game:
Play mana rocks like Mind Stone or Charcoal Diamond to accelerate.
Deploy your first 1–2 Relentless Rats to start the swarm.
Use spot removal (Tragic Slip, Hero’s Downfall) to keep the board manageable.

Mid-Game:
Establish card advantage with Phyrexian Arena or Ambition’s Cost.
Tutor or draw into Thrumming Stone and Karumonix.
Begin your ripple turns by casting any Relentless Rat.

Late Game:
Chain multiple Relentless Rats via ripple, flooding the board in a single turn.
With Karumonix in play, even 10 damage can become lethal via toxic.
Use Echoing Return or Secret Salvage to refill your hand or rebuild after a wipe.
Finish the game with proliferate engines like Contagion Engine or Karn’s Bastion.
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How the Combo Works

The Core Swarm:
Relentless Rats grow in power with every other copy in play. Playing just one becomes lethal with enough on the board.

Thrumming Stone + Ripple 4:
Every time you cast a Relentless Rat, you reveal the top 4 cards of your library. Every Rat revealed can be cast for free, triggering ripple again. This can result in 10–15 Rats in one turn.

Toxic Win Condition:
Karumonix gives all Rats toxic 1. If 10 unblocked Rats attack, that's an automatic win via infect regardless of life total.

Resilience through Recursion:
Echoing Return brings all Rats from the graveyard to your hand. Secret Salvage exiles one Rat to draw every other copy from your deck.

Proliferation for Pressure:
Contagion Clasp, Contagion Engine, and Karn’s Bastion allow you to multiply poison counters rapidly if your initial toxic hits don't finish the job.
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Sideboard Strategy

Against Aggro Decks:
2x Toxic Deluge – Efficient board wipe that scales.
2x Echoing Decay – Clears tokens or weenie swarms.

Against Control Decks:
2x Duress – Strip counterspells or sweepers early.
1x Pithing Needle – Stop planeswalkers or activated combo pieces.

Against Combo Decks:
1x Grafdigger’s Cage – Disrupts tutors and graveyard cheats.
2x Tormod’s Crypt – Stops reanimation and dredge strategies.

Against Enchantments/Artifacts:
2x Feed the Swarm – Removes problematic enchantments or artifact locks.
1x Karn’s Sylex – Stops activated abilities and sweeps nonland permanents.

Against Wide Boards or Combat Killers:
1x Ensnaring Bridge – Slows aggro to a crawl if you’re low on cards.
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Skill Level and Playability

Swarm of Vermin is ideal for players who love tribal synergy with a surprise combo twist. It rewards sequencing, deck knowledge, and swarm tactics. Managing combo turns and recursion lines is key to victory.

Difficulty Level: Intermediate
Playstyle: Explosive tribal combo with infect pressure
Best For: Both 1v1 and multiplayer casual Legacy
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Quote:
"They came not by dozens, but by hundreds. By the time you saw them, it was already too late."

Last Update: 09/05/25