According to the lore of "Beckoned by the World Chalice", the "Krawlers" are the enemies of the "World Chalice". Their names and designs are based on the human nervous system, save for Deus X-Krawler's name.
|Axon||Destroys a targeted Spell/Trap on the field.||Axon|
|Dendrite||Sends a monster from the controller's Deck to the GY.||Dendrite|
|Deus X-||Negate the activated effects of face-up monsters your opponent controls while face-up on the field.||Deus ex machina|
|Glial||Special Summons a "Krawler" monster from the controller's hand or GY in Attack Position or face-down Defense Position, except "Glial".||Neuroglia|
|Ranvier||Adds up to 2 targeted "Krawler" monsters in the controller's GY to their hand.||Ranvier|
|Receptor||Adds a "Krawler" monster from the controller's Deck to their hand.||Receptor|
|Spine||Destroys a targeted monster on the field.||Spine|
The "Krawler" archetype's main goal focuses upon using sheer numbers to overwhelm the opponent by swarming the field with as many of its monsters as possible. As the archetype is primarily comprised of Flip monsters, there is a focus in first getting them flipped face-up in order to trigger their Flip effects, putting them in a position to then accomplish said main goal. The archetype does this through effects possessed on all of its monsters whereby two "Krawler" monsters are Special Summoned when the monster is removed from the field due to an opponent's card effect, effectively doubling the controller's field presence as a result. As the monsters need to be face-up for the effect to activate and said effect Special Summons more "Krawler" monsters face-down, this provides an incentive for the controller to first flip them face-up in order to utilize the Flip effects, then have the opponent remove them with a card effect in order to make full use of both effects. In order to ensure that this shared effect can trigger, the archetype also has a secondary aim of restricting the opponent's moves by complicating their attempts to remove its monsters from the field through destruction by battle.
The archetype's Main Deck monsters are completely comprised of Flip monsters, each with two effects. The first effect is a Flip effect that is unique to the monster, and focus upon either advancing the player's resources or destroying cards on the field. The second effect is a common Trigger Effect that activates if they leave the field due to an opponent's card effect while face-up and controlled by their owner, enabling the controller to Special Summon 2 "Krawler" monsters with different names from their Deck in face-down Defense Position, with the exception of a monster that has the same name as the monster that left the field.
The archetype's Link Monsters, all being Link 2 and able to be Link Summoned using 2 members of the archetype, all share a common effect wherein if they leave the field by being destroyed by battle or due to an opponent's card effect while face-up, the controller can Special Summon 2 "Krawler" monsters from their GY in face-down Defense Position, once again increasing their field presence and enabling the controller to perform another Link Summon later on. This effect also forces the opponent into a position whereby any form of removal will trigger it, thus playing into the archetype's strategy of manipulating the opponent's removal options. The archetype's Link Monsters also possess unique effects that augment the battling capabilities of its monsters, making up for their low ATK and enabling the archetype to be a capable threat in battle.
"X-Krawler Neurogos" and "X-Krawler Synaphysis" share many common traits, namely that both possess Left and Right Link Arrows, and grant "Krawler" monsters linked to them 300 ATK and DEF, and indestructibility by battle. The latter trait is particularly useful for the archetype, as it further cuts off the opponent's options in removing the archetype's monsters by battle and forces them to use card effects, thus triggering the common effect of the Flip monsters. Additionally, "Neurogos" doubles the battle damage that "Krawler" monsters linked to it inflict upon the opponent, while "Synaphysis" enables "Krawler" monsters linked to it to make 2 attacks on the opponent's monsters during the Battle Phase, traits that further bolster the archetype's capability to inflict mass damage to the opponent in concert with its ability to swarm.
Due to the positioning of the Link Arrows for "Neurogos" and "Synaphysis", the controller can only take advantage of their linked effects while they are in Main Monster Zones. However, the controller can use this trait to their benefit, as for greater protection, copies of "Neurogos" and "Synaphysis" can be co-linked to each other, enabling them to mutually increase each others' ATK and protect each other from battle destruction, traits that they can bestow upon other "Krawler" Monsters, but not themselves.
While it possesses stronger unique effects than "Neurogos" or "Synaphysis", "X-Krawler Qualiark" is heavily dependent on the archetype's ability to swarm, as it applies its effects based on the number of "Krawler" monsters that the controller controls. However, like the unique effects of "Neurogos" and "Synaphysis", such effects provide potent boosts to the archetype's battling capacities. Should the controller control 2 or more "Krawler" monsters, the ATK and DEF of all monsters the player controls are bolstered by 300, similarly to the common effect of "Neurogos" and "Synaphysis". The controller controlling 4 or more "Krawler" monsters prohibits the opponent from activating cards and effects during the Battle Phase. Finally, if the controller controls 6 or more "Krawler" monsters, monsters they control can attack the opponent directly. Because "Qualiark" possesses Bottom-Left and Bottom-Right Link Arrows, it serves the archetype best if it occupies the controller's Extra Monster Zone, as in that role, it can act as an initiator for other Link Summons and facilitate the ideal placement of copies of "Neurogos" and "Synaphysis" in the Main Monster Zones, and by extension, the construction of a series of such monsters co-linked with each other in order to reap mutual benefits.
Given that the archetype is related to the "World Legacy" archetype, it also enjoys some support from that archetype's cards. The archetype's associated "World Legacy" monster, "World Legacy - "World Armor"" can be Special Summoned from the controller's hand when a monster is Flip Summoned, which can be easily enabled within the archetype. However, should it be Normal or Special Summoned, "World Armor" possesses an effect wherein the controller can search out a "World Legacy" card from their Deck to add to their hand, providing the controller with a way to search out support for either its archetype or the "World Legacy" cards connected to the "Krawler" archetype. Additionally, if it was Normal Summoned or Set, "World Armor" also has a Quick Effect that allows the controller to return both itself and a face-up monster controlled by the opponent that was Special Summoned from the Extra Deck to the hand, allowing for the removal of such monsters that may threaten the controller's efforts to build a field with "Krawler" monsters. Despite "World Armor" being a Level 7 monster, it can easily be Normal Summoned or Set in a "Krawler" deck, as the archetype provides ample Tributes for it due to its common effects. Due to its high ATK and DEF, "World Armor" also allows the archetype a way to cover for the fact that its own monsters tend to be lacking in those stats.
The archetype's associated "World Legacy" Field Spell, "World Legacy in Shadow" has an shared effect with other "World Legacy" Field Spells in that it bolsters the ATK and DEF of the associated archetype's monsters by 300. Additionally, "Shadow" has two unique effects, the first being that it allows the controller to Special Summon a Level 2 or lower Insect monster from their hand in face-up or face-down Defense Position, giving the archetype a more reliable way to amass field presence either to initiate their swarming capabilities or gather monsters to use as Link Materials for a Link Summon. The second unique effect of "Shadow" triggers in response when the controller's Flip monster is destroyed by battle by an opponent's monster, allowing the controller to send that opponent's monster to the GY, which serves as a way to further dissuade the opponent from attacking "Krawler" Flip monsters and preventing their common effects from triggering. Because the opponent might be more weary of attacking Set monsters as a result of this effect, it also allows the controller a greater opportunity to Flip Summon the archetype's monsters themselves, providing a more reliable way to Special Summon "World Armor" via its Summoning condition.
In a pinch, "World Legacy Pawns" allows the controller a quick way to trigger the Flip effects of the archetype's Flip monsters, as it possesses an effect that can change a face-down monster the controller controls to face-up Attack or Defense Position. This is particularly useful if the opponent attempts to remove the controller's face-down "Krawler" monsters with card effects, as this effect will ensure that such monsters are face-up instead when they leave the field and can thus activate their common effects. "Pawns" also has another effect whereby the controller can return a "Krawler" monster from their GY to their Deck to flip a face-up monster they control face-down. Such an effect alleviates the fact that the archetype can potentially thin the Deck very quickly, especially if the controller is successful in consistently utilizing the common effects of the Flip monsters, while also enabling the controller to re-use the Flip effect of a "Krawler" monster.
Due to the archetype largely consisting of Flip monsters, "Book of Eclipse", "Book of Moon", and "Book of Taiyou" can be used to great effect to trigger their Flip effects or Set them face-down again. As the archetype is reliant on Link Summoning its Link Monsters as quickly as possible in order to enable that its Flip monsters are reliably protected from battle destruction, cards such as "Multiplication of Ants", "Worm Bait", and "Spider Egg" can help in Special Summoning Token monsters to use as Link Materials, making up for the fact that the archetype can be slower to initiate its swarming capacity compared to other archetypes. If the controller is unable to dissuade the opponent from destroying "Krawler" Flip monsters by battle, "Verdant Sanctuary" can be a viable option in order to prevent the controller from losing card advantage should their monsters be destroyed, though it can also be used in concert with the common effects of the "Krawler" Flip and Link Monsters as well.
Due to the tendency of the archetype's Flip monsters to be sent to the GY either because they were flipped face-up and destroyed by battle, or because their common effects were triggered, it is easy for them to accumulate such monsters in the GY. "Aztekipede, the Worm Warrior" and "Doom Dozer" can turn such cards into a utilizable resource by banishing them to facilitate their Special Summons. The latter also provides the Deck with a strong attacker to make up for most of the archetype's monsters having low ATK. The fact that the archetype's Flip monsters have low ATK and DEF can also be capitalized upon by including "Danipon", "Gokipon", and "Howling Insect" to the Deck, as all of them can be Set and easily destroyed by battle to search out the archetype's Flip monsters, with the latter two cards being able to search out any of those monsters. The first two cards are also Level 2, allowing for synergy with "Shadow" or "Verdant Sanctuary". "All-Out Attacks" is a useful option for the Deck in order to trigger the Flip effects of the archetype's monsters, by forcing the opponent to attack them. It can also be used in conjunction with "Shadow" to send the newly Summoned monsters to the GY, further disrupting the opponent's attempt to gain advantage.
Since most Krawler cards have low attack, you can use cards like Full-Force Strike or Moon Mirror Shield to destroy your opponent's monsters in battle. Moon Mirror Shield works particularily good, since destroying it only puts it back into your deck (with the price of 500 LP), and removing your Krawler monster from the field will trigger it's effect, making it a deadly combo.