Evilswarm

The graveyard is the engine that keeps Evilswarm moving. Evilswarm Kerykeion banishes one "lswarm" monster from the graveyard to recover another, then rewards that exchange by granting an additional Normal Summon, giving the deck a steady stream of Level 4 bodies without burning through the hand. That flow of monsters feeds directly into Rank 4 Xyz Summons, and the deck's entire midgame is built on making those Summons as efficiently and repeatedly as possible.

Evilswarm Ophion is the centrepiece of that plan. While it holds Xyz Material, neither player can Special Summon Level 5 or higher monsters, which closes off Extra Deck plays from a large portion of the format. Its second effect searches any "Infestation" Spell or Trap, most importantly Infestation Pandemic, which protects Evilswarm monsters from targeting effects and keeps Ophion on the field long enough to be meaningful. Evilswarm Mandragora supports this by Special Summoning itself from the hand whenever the opponent has more monsters, ensuring the deck can still make its Rank 4 plays even when behind on board.

The suite of Xyz monsters beyond Ophion covers a range of situations: Evilswarm Nightmare flips incoming Special Summons face-down, Evilswarm Bahamut steals an opponent's monster at the cost of discarding another "lswarm" card, and Evilswarm Exciton Knight punishes any moment the opponent builds a larger board than the Evilswarm player can answer conventionally. Because the lock Ophion creates is static rather than guaranteed, the deck is vulnerable to strategies that play entirely within Level 1–4 range or that establish their board before Ophion can be summoned.