Executive Summary

The "lswarm" archetype is a DARK-Attribute strategy focused on Rank 4 Xyz Summoning to establish powerful anti-meta floodgates. Primarily composed of corrupted versions of other monsters, the archetype's main goal is to summon Evilswarm Ophion, a potent boss monster that completely shuts down the Special Summoning of Level 5 or higher monsters. With its straightforward control-oriented playstyle and powerful support cards, the archetype aims to simplify the game state and prevent opponents from accessing their most powerful extra deck monsters. Following the November 2025 ban of Evilswarm Ouroboros, the deck has pivoted from its classic, brittle builds. It now adopts new engines like "Fiendsmith" and a more flexible, superior 2-material Rank 4 toolbox to maintain its competitive edge. The full extent of their corrupting influence is a testament to their anti-meta design.

The Swarm's Vanguard

Core Monsters

Evilswarm Castor

The primary starter. Grants an additional Normal Summon for a "lswarm" monster, enabling an instant Rank 4 Xyz Summon.

Evilswarm Kerykeion

The main extender and recovery tool. It can banish a "lswarm" from the GY to add another to hand, and grants an extra Normal Summon.

Evilswarm Mandragora

A free Special Summon from the hand if the opponent controls more monsters than you, providing easy material for an Xyz Summon.

Rescue Rabbit (Obsolete)

Classic 1-card starter with 3x Evilswarm Heliotrope. Now considered obsolete due to high variance ("bricking" on Heliotrope) and superior modern engines.

The Extra Deck Toolbox

Evilswarm Ophion

The deck's signature boss monster. While it has Xyz Material, Level 5 or higher monsters cannot be Special Summoned. It also searches for "Infestation" Spell/Trap cards.

Evilswarm Ouroboros (FORBIDDEN)

The classic 3-material boss. Banned in Nov 2025 not for 'lswarm' use, but for "hand loop" abuse in other decks. Its loss is a net positive.

Infestation Pandemic

The primary protection card. This Quick-Play Spell makes all face-up "lswarm" monsters you control unaffected by other Spell/Trap effects for the turn.

Mandatory Modernization: The 'Fiendsmith' Engine

Fiendsmith Engraver
Missing: 60764609

Solving 'lswarm's' Core Weakness

The classic 'lswarm' deck was critically over-reliant on its Normal Summon (e.g., "Castor"). If that one summon was negated, the turn would end. The "Fiendsmith" engine is a mandatory upgrade that solves this problem.

  • Provides 1-Card Starters: "Fiendsmith's Tractus" starts plays without using the Normal Summon.
  • Resilience: Provides extenders ("The Fiendsmith") and a parallel line of play to bait disruption *before* committing to the 'lswarm' Normal Summon.
  • Consistency: Replaces the high-variance "Rescue Rabbit" engine, as its pieces have utility even when drawn individually.

Core Combo: Summoning the Ophion Lock

Unverified AI Content
This combo line is AI-generated and may contain errors or illegal plays (e.g., banned cards).
Know the correct line? Submit a Replay to fix this guide

This remains the deck's primary goal against meta decks reliant on high-level monsters, like Branded or Memento.

Evilswarm Castor
Missing: 79785958
1

Initiate the Swarm

Normal Summon Evilswarm Castor. Activate its effect to gain an additional Normal Summon.

Evilswarm Ophion
Missing: 91279700
2

Establish the Lock

Normal Summon another Level 4 "lswarm" monster. Overlay both monsters to Xyz Summon Evilswarm Ophion.

Infestation Pandemic
Missing: 27541267
3

Secure and Protect

Activate Ophion's effect by detaching one material to search for Infestation Pandemic from your deck. Set it for protection on the opponent's turn.

Addition by Subtraction: The New Toolbox

The Ouroboros ban forces the deck to use a superior, cheaper (2-material), and more flexible set of generic Rank 4 Xyz monsters. This is the deck's new "Pivot" strategy against low-level decks like Yummy Mitsurugi, or as secondary floodgates.

Board Stun

Number 41: Bagooska the Terribly Tired Tapir
Missing: 90590303

Number 41: Bagooska

The new default "going-first" play against unknown or Xyz/Link decks. Its stun effect buys critical time where Ophion's floodgate would be useless.

Superior Removal

Time Thief Redoer
Missing: 55285840

Time Thief Redoer

Directly replaces Ouroboros's bounce. It's a Quick Effect (faster), costs 2 materials (cheaper), and spins to deck (stronger).

Superior GY Hate

Abyss Dweller
Missing: 21044178

Abyss Dweller

Directly replaces Ouroboros's banish. It's an infinitely more powerful floodgate that stops *all* GY effects for a turn. Critical vs. Branded/Memento.

Typical Endboard

The "Protect the Castle" Pivot

The optimal endboard now depends on the matchup. The "Ophion" lock is for high-level decks, while the "Origin / Bagooska" lock is for low-level decks.

Pivot A (vs. Branded)

Evilswarm Ophion
Missing: 91279700
+
Infestation Pandemic
Missing: 27541267

Pivot B (vs. Yummy)

Number 41: Bagooska the Terribly Tired Tapir
Missing: 90590303
or
Steelswarm Origin
Missing: 61888819

Competitive Analysis

Strengths

  • Powerful Floodgate: Ophion's effect is devastating against meta decks reliant on high-level monsters (Branded, Memento).
  • Excellent Protection: Infestation Pandemic provides crucial protection against common board-breaking Spells and Traps.
  • Resilient (Modernized): With the "Fiendsmith" engine, the deck is no longer reliant on a single Normal Summon and can play through disruption.

Weaknesses

  • Binary Matchups: Highly matchup dependent. Has auto-win matchups (Branded) and auto-loss matchups (Yummy Mitsurugi) in Game 1.
  • Vulnerable to Negation: The *classic* 'lswarm' combo is still vulnerable, though "Fiendsmith" builds significantly mitigate this weakness.
  • Limited Recovery: Can struggle to rebuild its board once the primary lock is broken, though Kerykeion helps.

Tech Choices & Hybrids

  • "Fiendsmith" Engine: A mandatory modernization for resilience and 1-card starters.
  • Modern Rank 4 Toolbox: Bagooska, Time Thief Redoer, and Abyss Dweller are now core.
  • Steelswarm Origin: A key pivot, provides a different lock vs. Xyz/Link decks that Ophion cannot stop.
  • Floodgate Traps: Cards like "There Can Be Only One" or "Gozen Match" are critical for siding against bad matchups.

Banlist Impact

SIGNIFICANT IMPACT: The lswarm archetype faces significant restrictions on the TCG banlist with Evilswarm Ouroboros forbidden.

Archetype Cards

Forbidden

  • • Evilswarm Ouroboros

Synergistic Cards

Forbidden

  • • Abyss Dweller

Meta Implications: The loss of Evilswarm Ouroboros significantly impacts the archetype's power level and consistency. Players will need to adapt their strategies accordingly.

Banlist Status Summary

+ analyzed • 2 total restrictions found • 1 archetype card1 synergistic card