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"Koa'ki Meiru", Japanese for "Core Chimail" (コアキメイル Koakimeiru), a combination of the words "Core", "Chimera" and "Mail"), sometimes romanized as "Core Chimair" (a combination of the words "Core" and "Chimera,") is an archetype debuted in Raging Battle.
"Koa'ki Meiru Rooklord", "Sea Panther", "Urnight" and "Valafar" all appear as characters in Yu-Gi-Oh! 5D's World Championship 2010: Reverse of Arcadia, and "Maximus" appears in Yu-Gi-Oh! 5D's World Championship 2011: Over the Nexus.
The "Koa'ki Meiru" archetype consists of a plethora of different creatures, featuring elementals, dragons, statues, warriors and many more and can overall be described as a mishmash of art styles. They don't really have any connection in design or color, except for the fact that all of the "Koa'ki Meirus" have the same mark (3 dragons) on some part of their body or on a weapon they use.
The majority of the effects of "Koa'ki Meiru" cards center around manipulating "Iron Core of Koa'ki Meiru" or revealing one in your hand to activate an effect. Almost all of the monsters require a maintenance cost in the form of sending an "Iron Core" to the Graveyard or revealing a monster of the same type. However, there are exceptions to this rule:
- "Koa'ki Meiru Hydro Barrier" and "Koa'ki Meiru Tornado", both monsters without the normal maintenance cost of "Koa'ki Meirus".
- "Koa'ki Meiru Powerhand", for which you must reveal a Normal Trap Card instead of a Machine monster.
- "Koa'ki Meiru Ice", who requires a Continuous Spell Card to be revealed instead of an Aqua monster.
- "Koa'ki Meiru Valafar", who doesn't have a reveal option at all, forcing you to ditch an "Iron Core" to keep him alive.
- "Koa'ki Meiru Maximus", who has two discard effects as maintenance instead of one discard and one reveal effect.
"Koa'ki Meiru" monsters are all EARTH, WIND, WATER or FIRE Attribute monsters, rendering them immune to their own control-based effects, which often negatively affect LIGHT and DARK monsters. The entire theme was initially designed to bring down the dominating Decks at the time of over 2 banlists and therefore centered around heavy control elements. Seeing as the meta was completely dominated by LIGHT and DARK Decks, their effects were specifically designed to target both Attributes, therefore inviting a specific "Anti-Meta" theme to the "Meta" at the time. Because of their high ATK for monsters of their level, with many Level 4 monsters in the archetype having 1900 ATK or 2000 ATK, and boss monsters topping out at 3000 ATK, the archetype has taken a more aggressive approach with powerful beatdown elements.
Generally speaking, there are two ways to use "Koa'ki Meiru" cards. The most obvious is simply to use a dedicated Deck; the other way is to use individual "Koa'ki Meiru" monsters as a supplement to Type-specific Decks of their type, giving an "Anti-Meta" controlling aspect to it as well as being able to maintain it through the alternative maintenance cost; for example, using "Koa'ki Meiru Drago" in a Dragon Deck as seen back in the day in "Disaster Dragon" builds. When "Koa'ki Meiru" first came out, the sole purpose of the Deck was the "Anti-Meta" aspect. However, nowadays the deck needs to use a different approach, since simply hating against certain Attributes doesn't quite make the cut anymore. Surprisingly though, a decent number of "Koa'ki Meiru" cards is still solid and allows them to at least build a functional Casual deck.
In order to run a dedicated "Koa'ki Meiru" Deck, no matter the style, you'll need multiple ways to retrieve the "Iron Core of Koa'ki Meiru" from your Deck and Graveyard. The number one card to fetch the "Iron Core" is "Diamond Core of Koa'ki Meiru", which not only conviently searches the entire archetype (with exception of some Spell/Trap support that doesn't have "Koa'ki Meiru" in the name), but also protects your monsters from being destroyed for a round. Additional options include "Koa'ki Meiru Boulder", a battle searcher, "Koa'ki Meiru Crusader", who searches upon destroying stuff in battle and "Core Transport Unit", which simply fetches the "Iron Core" for the cost of one card. "Iron Core Immediate Disposal" can also be a way of getting an "Iron Core", but is card economy-wise not the best strategy. Due to the fact that "Iron Core" is retrieveable from the GY, any Cards that help thin the deck or dump the "Core" into the Graveyard help make the Deck faster and more consistent. You must also be wary of keeping more monsters on your field than you can maintain. Your field should max out at 2 "Koa'ki Meiru" monsters requiring maintenance with multiple "Cores" as well as an alternative cost ready in hand. If the maintenance cost would force you to destroy monsters during the End Phase, you can plan ahead and decide to overlay them into Xyz Monsters or use them for Link Summons in Main Phase 2.
Before getting any deeper into deck building and strategy, it should be mentioned that probably the most well-known and popular build with "Koa'ki Meiru" is the so-called "Rock Stun" deck. It uses "Koa'ki Meiru Wall", "Koa'ki Meiru Sandman", "Koa'ki Meiru Guardian", "Koa'ki Meiru Overload" and "Koa'ki Meiru Boulder", all Rock-type monsters of which the first four are able to tribute themselves to counter certain cards and/or effects, while the last one searches the others. But while the deck features a good number of "Koa'ki Meirus", it is explained in detail on its own page and will not be further discussed here.
The most important card in any pure "Koa'ki Meiru" Deck is "Iron Core of Koa'ki Meiru", so having three in your Deck is absolutely essential."Koa'ki Meiru" Decks can take advantage of the negation effects of the aforementioned "Wall", "Sandman", "Guardian" and "Overload", but the archetype features way more cards than the four stun monsters. The card advantage of "Koa'ki Meiru Crusader" can certainly be helpful at times and "Koa'ki Meiru Urnight" brings incredibly helpful swarming capabilities for almost no requirements; also, they are both Beast-Warriors, allowing some other cards like the "Fire Formations" to become reasonable additions. Both "Koa'ki Meiru Ice" and "Koa'ki Meiru Tornado" are wonderful in punishing your opponent's powerful Special Summoned monsters and the effect negation of "Koa'ki Meiru Hydro Barrier" can be devastating if timed correctly. For the Beatdown part of the archetype, use the Warrior-monsters "Koa'ki Meiru Bergzak" and "Koa'ki Meiru Rooklord", both able to clear the way through the opponent's board. "Koa'ki Meiru Drago" and "Koa'ki Meiru Maximus", the two dragons of the archetype also feature some useful effects, but as mentioned before, "Drago" is more useful in a Dragon-type deck that wants an out against LIGHT and DARK decks. "Maximus" is often a dead draw early on, and is difficult to maintain once it hits the field, but can help clear the field before swinging into the opponent, making it a very powerful but also very temperamental boss monster. "Koa'ki Meiru Ghoulungulate" has a protection effect which can be easily achieved by first fueling the Graveyard with "Iron Core Specimen Lab", but sadly is Level 5, making it subpar due to better options for Tribute Summoning. "Koa'ki Meiru Beetle", "Koa'ki Meiru Doom" and "Koa'ki Meiru Powerhand" join in with the LIGHT/DARK hate with position changing and effect negation, "Koa'ki Meiru Prototype" gives recovery and a pseudo-"Iron Core" effect, "Koa'ki Meiru Speeder" lets you plus from recovering "Iron Cores", "Koa'ki Meiru Sea Panther" slowly recovers Spell Cards, "Koa'ki Meiru Valafar" is a trap-proof, piercing boss monster and both "Koa'ki Meiru War Arms" and "Koa'ki Meiru Gravirose" interact with monsters that hardly exist in the archetype.
"Koa'ki Meiru" also has a number of cards that are functionally similar to certain generic cards: “Core Reinforcement” is basically a “Call of the Haunted” but worse, “Automatic Laser” functions similarly to “Bottomless Trap Hole” with a wider range but the need for an “Iron Core”, “Koa'ki Meiru Shield” is a inferior version of “Mirror Force” and “Nega-Ton Corepanel” is a variant of “Divine Wrath” without the cost of discarding a card but the need for both a “Koa'ki Meiru” monster as well as an “Iron Core” in the Graveyard.
Due to the importance of "Iron Core", there is a number of cards that were made specifically to search it. Aside from "Diamond Core of Koa'ki Meiru", "Iron Core Immediate Disposal" and "Core Transport Unit", which were mentioned before, there is "Koa'ki Meiru Initialize!", which effectively trades a monster for an "Iron Core". "Koa'ki Meiru" also comes with it's own draw spell in "Core Compression", an ATK booster in "Core Overclock", an equipable "Iron Core" in form of "Iron Core Armor", equipable LIGHT/DARK hate via "Core Blaster" and some specific destruction effects by the trio consisting of "Core Blast", "Koa'ki Ring" and "Reckoned Power". Finally, as the direct opposite of "Koa'ki Meiru Initialize!", there is "Urgent Synthesis" which trades an "Iron Core" for a monster.
In terms of deck building, "Koa'ki Meiru" is a relatively straight-forward deck: Max "Iron Core" is paramount, as is "Diamond Core" for being one of the best search Spells in the game while granting destruction immunity when needed. "Koa'ki Meiru Urnight" searches for more monsters for added pressure as well as an easy way into Xyz and Link monsters. Reasonably good targets for "Urnight" include "Koa'ki Meiru Crusader" for being another Beast-Warrior with searching capabilities and "Koa'ki Meiru Bergzak" for added power. "Bergzak" actually profits from any sort of ATK boost, making "Core Overclock" a possible choice for the deck. Depending on what the opponent ends his turn with, one can Normal Summon "Urnight", use its effect and reveal an "Iron Core", summon "Bergzak" from the deck, playing "Core Overclock" and discarding the previously revealed "Core" for an extra ATK boost, potentially ending the opponent then and there if no out is available due to two attacks from "Bergzak" and one from "Urnight", each for 3500 ATK. "Koa'ki Meiru Rooklord" is a solid choice for a Tribute Monster with his in-build "Icarus Attack" and "Core Compression" helps with the overall consistency. Both "Reinforcement of the Army" and "Fire Formation - Tenki" search for key members of the deck, and with further generic or other archetypal support, both "Isolde, Two Tales of the Noble Knights" and "Fire Fighting Daruma Doll" can further strengthen the deck.
- A major weakness is the archetypes own maintenance effect. If the player is not careful and summons multiple "Koa'ki Meiru" monsters to the field without thought, it can easily blow up if one is not able to pay all the costs.
- Because "Iron Core of Koa'ki Meiru" will often be recycled from the Graveyard, the "Koa'ki Meiru" deck is vulnerable to cards that can banish it such as "Gladiator Beast Retiari", "D.D. Crow", "Macro Cosmos" or the like.
- "Necrovalley" is a potential counter to "Koa'ki Meiru", since it prohibits "Iron Core" to leave the GY and therefore makes recycling it impossible.
- "Koa'ki Meiru" monsters are very reliant on the hand, therefore any form of "Hand Control" presents a big threat by being able to specifically remove assets essential to the Deck. Cards like "Card Destruction", "Mind Crush", "D.D. Designator" and "Trap Dustshoot" can completely disrupt the player's strategy.
- While relatively uncommon, a way of countering "Koa'ki Meiru" is playing "Prohibition", since locking the deck out of "Iron Core" will make it more difficult to keep monsters alive due to maintenance.
- One way to beat the "Koa'ki Meiru" archetype is to have the player permanently reveal their hand to you in order to make them either discard an "Iron Core of Koa'ki Meiru" or destroy the card since they cannot "reveal" the card to you. Such cards include "Respect Play" and "Ceremonial Bell".
- Like many other decks, "Koa'ki Meiru" does not appreciate its Summons to be negated or blocked. "Solemn Warning", "Solemn Judgment", "Archlord Kristya", "Vanity's Fiend" or "Vanity's Emptiness" are all effective against the deck.