Algright: I've given this deck some thought, and have changed a few things from it's previous incarnation. My goal is to build a set of Krawler decks, exploring the combos that exist and trying to solve the deck's main problems. This build will focus on pure Krawlers, no other main-deck engine, but I plan on making a few other builds exploring Krawler/Shaddoll, Krawler/Subterror, Krawler/Ghostrick, and Krawler/Ninja, to name a few. Do I believe my build pushes Krawlers to their limit; have I achieved peak Krawling perfection? No, but I hope this list will inspire others to seek this goal with me.
Before I get into the card-by-card, I want to explore what Krawlers do well, what they lack, and how we can push them to their limits. Krawlers lack draw power. Their only two in-archetye options to fetch cards are World Legacy Survivor and Krawler Receptor, but both only find one card. You could play Receptor with Book of Taiyou to gaurantee fingin Soma, but I've found Taiyou to be difficult to draw into. Krawler's also have very conditional floating effects that only trigger off of opponent's card effects, and only when the monster is face-up. Finally, Krawlers traditionally represent very little interaction on the opponent's turn. Maybe one or two flip-effects activating to deal with the opponent's summons, and most decks can play through that. To fix the difficulties this deck faces, we are including search cards like Small World and Pot of Desires. We are using Guard Dog and Morphing Jar #2 to provide stronger interruption to the opponent, and several hand-traps to supplement our plays. We are also using Junk Sleep to guarantee activations and to allow us to re-use our flip effects. And we are protecting our mons with cards like Lord of the Heavenly Prison and Calamity Upon the Hidden City. What do Krawlers do well? They float into 2 Krawlers, and have a great variety in their card effects! From Spell/Trap or monster destruction, to dumping any monster from deck to grave, they cover quite a wide spectrum. Also, with the new support in Krawler Soma, this deck can very easily get four monsters on the field with just two cards! If we use the tools this archetype provides to the best of our ability, it can grind an opponent out of resources and win us a war of attrition, if we don't lock the opponent out of the game completely!
Let's get the easy stuff out of the way. We're playing 2 Nibiru, The Primal Being to clean up the opponent's board, and because Nibiru doesn't destroy facedowns, of which we have many! (Thanks to IDE-eyes for this!) All of our handtraps and once-per-turn cards are at two because we lack draw power in this list, and drawing multiples of these cards is extra painful. We're also on 2 Ash Blossom, 2 Infinite Impermanence, and 2 Dark Ruler for extended games and going second. I put 2 copies of Lord of the Heavenly Prison in to protect our backrow and our set monsters, and the card we will be searching with them is most often either Small World or World Legacy Survivor. The 2 Pot of Desires are our best draw card (prosperity would be better, but the price is killer), and the goal is to use it after searching with Small World or World Legacy Survivor to preserve our bridges and our key cards. The 1 Ghostrick Shot and 1 Ghostrick Scare are here for the extra deck Ghostrick to Utopic Future line. 1 Called by the Grave is crucial to avoid hand-traps. Possibly the most important cards in this list are our 2 copies of Small World (3 is better for consistency, but I found it to brick too many times, and we need all the cards in our hand to be usable). I will go over our bridges at the bottom, but just know that this card is our primary way of finding Soma, and once we have Soma, our primary way of finding Guard Dog or Morphing Jar #2.
Now for the fun stuff! The meat of the deck! Our primary card to flip our monsters face up, other than Ghostrick Scare (searched off of Angel of Mischief) is Junk Sleep. It flips all of our monsters, which while not as controlled as a card like World Legacy Pawns, does allow us to activate multiple flip effects on the opponent's turn. It also flips all of our cards face-down during the End Phase, which resets our flip mons and powers up the next card. Calamity Upon the Hidden City! This is a powerful addition to any flip deck, as it protects all face-down monsters from targeted effects. It also floats into any monster when it is destroyed by an opponent's effect, and it gives all monsters that we flip face-up a 1500 point Atk/Def boost! This increase stacks with multiple copies of Calamity, and applies to all monsters we flip up, and given that we will be flipping our monsters face down with Junk Sleep, this can often be enough to push for game. I only included the 1 copy of World Legacy's Mind Meld. It is a fantastic card, but this deck doesn't have reliable ways of putting traps in the grave, unlike the Girsu build which uses Lib to dump a Spell/Trap from deck. We hope to hit it off of World Legacy Survivor, or to use on the opponent's turn as additional disruption. We are playing 2 Guard Dog and 1 Morphing Jar #2 (inspired by Faith_SC's list) to stop the opponent's plays on their turn, and buy us enough time to either OTK or setup our board.
EDIT: now I'm playing Amano-Iwato in place of Morphing Jar #2. It can bridge into Girsu, and can be used to find Guard Dog.
We're on 1 Deus X-Krawler, a very powerful boss monster that Skill Drains the opponent's board. You could play 2 copies instead, I just don't want to brick on it. 3 copies of Krawler Soma, as Soma is the key to this deck. This new piece of support is just what the archetype needed! He allows for much faster plays than Krawler was used to, and if Soma is flipped down and back up again, their level resets so they can use their ability again next turn! The small Krawlers (smallers) are 1 Ranvier for recursion, 2 Receptor to search, 3 Glial to summon Deus X or Spine, 1 Axon if the opponent is playing backrow, and 2 Spines to remove monsters. In the extra deck, we are playing 2 Ghostrick Angel of Mischief, 1 Ghostrick Socuteboss, 1 Utopic Future, and 1 Utopic Draco Future as the payoff for this line. 1 Gigantic Spright is here to summon any small Krawler from deck and to extend our bad opens. Mekk-Knight Crusadia Avramax is a difficut mon for Spright and Tearlament to deal with. Borrelguard Dragon can flip our monsters on the opponent's turn and helps us to push our advantage. Knightmare Unicorn is crucial for dealing with destruction-proof cards. Subterror Behemoth Fiendess can cheat out Deus X-Krawler, or send it to the grave to be revived by Glial, and it searches! The rest of the extra deck is just the X-Krawler link mons.
Now that we have the deck profile out of the way, how do you play it and how does it win? Our goal with most starting hands is to draw or find Soma. We can use our Pot, Small World, Survivor, or potentially Receptor to find Soma. If we are going second, he is still crucial, but perhaps more important is finding one or two usable hand-traps to disrupt our opponent and provide and opening that we can sieze. If we started with Soma, or found it without using Small World, our next target for Small World is Guard Dog. Guard Dog locks the opponent out of all special summoning for the rest of the turn after they are flipped, and they are the optimal summon before Soma, most of the time (not against Floowandereeze for example). Morphing Jar #2 is the next best target (it can disrupt Floo), with the base Krawlers being the alternative option. Once we have a monster to normal summon and Soma in hand, we have a few branching choices. If World Legacy Survivor hasn't been used we can make Utopic Draco Future with two set monsters and a Ghostrick Scare set, with 3 remaining cards in hand. Otherwise, making Subterror Behemoth Fiendess with three set monsters or X-Krawler Qualiark with two set monsters is our play. We want the opponent to be forced to make inefficient trades with us, like popping Qualiark which will summon back 2 mons or destroying Guard Dog after it already got it's effect off, so they run themselves out of cards and options. Going second we are looking to clean up as much of the opponent's board as possible before setting up the same Guard Dog lock with other face-down cards and passing. This deck has a hard time winning in one turn, so we want to draw the game out as long as possible.
Lord of the Heavenly Prison helps to extend the game. If we can reveal this card, and have an active Calamity on board, the opponent cannot destroy our set cards, and they cannot target our set monsters! Once we activate our face-down, usually Junk Sleep or Ghostrick Scare, we can summon our Lord and search a Spell/Trap (Small World, Dark Ruler, and Pot are all great searches, as they will be banished at the end of our next turn). So, we have options for protecting our cards, stopping the opponent form making plays, and filling the board, and now we need to find lethal. Hopefully we have gotten lucky and found a Calamity. If not, we are going to rely on the X-Krawlers, specifically the attack boosts and combat effects, to push in once we have re-filled our board with Soma. If we have to play a slower game with Avramax or Borrelguard, we just look for chip damage each turn, while preserving our lock.
With some of the changes I made, we can also make El Shaddoll Winda with a set Deus X-Krawler on field! If you open Girsu and Soma, normal Girsu sending World Legacy Mind Meld and summon a token. Flip Girsu face-down to summon Soma, use Soma to summon two Krawlers face-up. Link the two flip-monster Krawlers into Shaddoll Construct, and fuse Construct with the face-down Girsu to make El Shaddoll Winda. Link Soma and the token for Lib the World Key Blademaster, and set World Legacy Pawns from deck. On the opponent's turn, use your Mind Meld in GY to summon Deus X-Krawler to a zone Lib points to.
Here are the Small World Bridges (they are all reversible):
Starter -> Bridge -> Result
Any Krawler / Amano-Iwato / Ash Blossom -> Guard Dog -> Any Krawler / Amano-Iwato / Ash Blossom
Nibiru / Lord of the Heavenly Prison -> Amano-Iwato -> Any Krawler / Guard Dog / Girsu
Any Krawler / Guard Dog / Girsu -> Amano-Iwato -> Nibiru / Lord of the Heavenly Prison
I really hope this breakdown was helpful; that it was informative and enjoyable! If you have any questions or comments, I would love to hear them in the comments down below! Have a great day!
EDITS: Included Sol and Luna, its a great card to draw. Included Girsu and the Shaddoll extra-deck package, which we can make off of Girsu. Swapped out Morphing Jar #2 for Amano-Iwato; they're a better bridge and do more for the deck.
PS: In the side deck are options that I've considered, but that I can't find a place for right now