"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 of cards primary from Raging Battle, Ancient Prophecy, Stardust Overdrive, Absolute Powerforce and The Shining Darkness. This archetype received more Anti-Meta and support cards in later sets Starstrike Blast, Primal Origin and Secrets of Eternity.
The majority of their effects center around manipulating the "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 grave or revealing a monster of the same type. There are exceptions, such as that of "Koa'ki Meiru Powerhand", where you must reveal a Normal Trap Card, or "Koa'ki Meiru Valafar" where you have to send an "Iron Core of Koa'Ki Meiru" and cannot reveal any card in your hand instead. Another is "Koa'ki Meiru Ice", where a Continuous Spell Card is revealed.
"Koa'ki Meiru" are all EARTH, WIND, WATER or FIRE Attribute monsters, rendering them immune to their own control-based effects, which often affect LIGHT and DARK monsters. All of the "Koa'ki Meiru" have the same mark (3 dragons) on some part of their body or on a weapon they have. Also, many "Koa'ki Meiru" and related cards' artwork uses yellow, orange, and red, except for "Koa'ki Meiru Ghoulungulate".
The theme was initially designed to bring down the dominating Decks of over 2 banlists and therefore centered around heavy control elements. Seeing as the meta was completely dominated by LIGHT and DARK Decks, effects specifically targeted both Attributes therefore bringing about a specific "Meta", "Anti-Meta" theme. Because of their high ATK, 11 Level 4 monsters from 1900 ATK, topping out at 3000 ("Koa'ki Meiru Valafar" and "Koa'ki Meiru Maximus"), and the nature of the new support, the theme has taken a more aggressive approach with powerful beatdown elements, namely "Koa'ki Meiru Rooklord" and "Koa'ki Meiru Urnight".
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 the "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-Type Deck as seen in "Disaster Dragon" builds.
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. Good cards for this include "Koa'ki Meiru Boulder", "Koa'ki Meiru Crusader", "Diamond Core of Koa'ki Meiru", and "Core Transport Unit". "Iron Core Immediate Disposal" is also nice mid game after building up resources in your hand. 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 on field than you can maintain. Your field should max out at 2 "Koa'ki Meiru's" requiring maintenance with multiple "Cores" in play as well as an alternative cost ready in hand. With this in mind it would be wise to play multiple cards of the same Type, making your field easier to maintain. However, with the release of Xyz Monsters, you can simply overlay any "Koa'ki Meiru" Monsters that you may not have a maintenance for.
Beatdown uses a different lineup, using a minimum of control but only the best in the form of "Koa'ki Meiru Rooklord" and "Koa'ki Meiru Drago". The main attackers are "Koa'ki Meiru Bergzak", "Koa'ki Meiru Powerhand" and "Koa'ki Meiru Rooklord". With the addition of "Koa'ki Meiru Urnight" from Absolute Powerforce, you gain a swarm/toolbox element. "Koa'ki Meiru Ghoulungulate" is nice protection but your tribute fodder is best used on "Rooklord". Spell/Trap protection is a better option.
Because "Iron Core of Koa'ki Meiru" may often be in the Graveyard it is vulnerable to cards that can banish it such as "Gladiator Beast Retiari" and "Macro Cosmos". Also, having multiple "Koa'ki Meiru" monsters on the field at once can be extremely dangerous as each one would require you to reveal a card or discard a card from your hand at the End Phase, leaving your hand and field advantage very hard to maintain unless multiple copies are used (for example, 3 "Koa'ki Meiru Powerhands" only require 1 Normal Trap Card revealed). A good way to avoid problems with this is to keep a duplicate of the specific monsters in your hand-usually, "Koa'ki Meiru" Monsters require you to reveal a monster of the same type so you can reveal a duplicate or another "Koa'ki Meiru" of the same type. "Koa'ki Meiru" monsters are very reliant on the hand and so cards like "Card Destruction", "Mind Crush", or "D.D. Designator" can completely disrupt the player's strategy and cards like "Trap Dustshoot" or even "Des Koala" can deal serious damage.
One way to beat the "Koa'ki Meiru" format is to have the opponent permanently reveal their hand to you on their turns 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". "Banish" Decks can banish "Iron Core of Koa'ki Meiru" and so you have to rely on your revealing effect. To protect yourself from this, it is a good idea to have "Necrovalley" and a "Burial from a Different Dimension" in your Side Deck.
"Hand Control" Decks present the biggest threat by being able to specifically remove assets essential to the Deck.
This Deck revolves around "Anti-Meta". Obviously, the most important card in the Deck is "Iron Core of Koa'ki Meiru", so having three in your Deck is a must. Most of the monsters are used against Effect Monsters, mostly DARK and LIGHT monsters, since they are the commonly used Decks ("Infernities", "Lightsworns", "Blackwings" etc.). Most Koa'ki Meiru Decks should focus on the negation effects of "Koa'ki Meiru Wall", "Koa'ki Meiru Sandman", and "Koa'ki Meiru Guardian" and the card advantage and swarming effects of "Koa'ki Meiru Crusader" and "Koa'ki Meiru Urnight" using the other "Koa'ki Meiru" Monsters according to the Deck's main strategy. In addition, "Koa'ki Meiru Ice" and "Koa'ki Meiru Tornado" are wonderful in punishing your opponent's powerful Special Summoned Monsters.
"Koa'ki Meirus" can also work well with support for Equip Spell Cards. Using cards like "Hidden Armory", "Iron Core Armor" can be recycled just as much as the "Iron Core" itself. "Core Blaster" is also extremely powerful, and even a single copy could destroy decks that focus heavily on LIGHT and DARK monsters. "Koa'ki Meiru Bergzak" works very well with any ATK-boosting effect, and "Iron Blacksmith Kotetsu" fits on the deck since it's a Beast-Warrior.
"Trade-In" can work well if you are using "Beast King Barbaros" or "Grandsoil the Elemental Lord" to reveal for "Koa'ki Meiru Urnight" and "Koa'ki Meiru Crusader". Other Level 8 monsters to work with "Trade-In" are "Koa'ki Meiru Valafar" and "Koa'ki Meiru Maximus".
It would be wise to include cards that return monsters and other cards to your or your opponent's hand. For example, "Compulsory Evacuation Device" or "Penguin Soldier" can both remove threats from the field or keep a "Koa'ki Meiru" alive for a turn or even using it for the maintenance.
Although most "Koa'ki Meiru" monsters have difficulty staying on the field, a few of them work incredibly well together, sharing types or common reveals that help ensure their survival on the field. However, because most are level 4, they can be used for an Xyz Summon before they are destroyed during the End Phase.
- "Koa'ki Meiru Urnight" and "Koa'ki Meiru Crusader" are Beast-Warrior-Type monsters and have the same reveal requirement, while allowing for a good presence on the field and card advantage. "Urnight" can Special Summon another level 4 "Koa'ki" from the Deck for a quick Xyz Summon and "Crusader" can recover "Urnight" after it has been detached.
- "Koa'ki Meiru Wall", "Koa'ki Meiru Sandman", "Koa'ki Meiru Guardian", "Koa'ki Meiru Boulder", "Koa'ki Meiru Prototype", "Koa'ki Meiru Overload" and "Gigantes" can be extremely aggressive when combined, as well as controlling the field and hand. "Wall", "Sandman", "Overload" and "Guardian" all have effect negation abilities: they are used for a "Rock Stun" deck. "Boulder" and "Prototype" are both extremely useful for "Koa'ki Meiru" monsters because they do not require the normal sacrifice-"Boulder" is used to search for other "Koa'ki Meiru" monsters or "Iron Cores", while "Prototype" can sacrifice itself to prevent a "Koa'ki Meiru" monster from being destroyed during the end phase of the turn.
- "Koa'ki Meiru Maximus" can be used as the reveal cost for "Koa'ki Meiru Drago". "Drago's" effect serves as disruption, while you gather "Iron Core of Koa'ki Meiru" for "Maximus's" final push for game. "Maximus" is often a dead draw early on, however; and it is difficult to maintain once it hits the field, making it a very powerful but also very temperamental boss monster. Use with caution.
- "Koa'ki Meiru Doom" and "Koa'ki Meiru Valafar" also work together, usually in a different Deck revolving around "Evil Hero Dark Gaia" and "Dark Fusion".
- "Koa'ki Meiru Speeder" can null the costs for "Koa'ki Meiru Tornado" and "Koa'ki Meiru Hydro Barrier", as well as working with "Koa'ki Meiru Powerhand" due to their high ATK and DEF and low Levels.
- "Koa'ki Meiru Ghoulungulate" has a protection effect which can be easily achieved by building up a good Graveyard size with "Iron Core Specimen Lab" and "Koa'ki Meiru Urnight". "Koa'ki Meiru Ghoulungulate" can easily be brought out with Pyramid Turtle's" effect, and keeps a good Tribute fodder for "Koa'ki Meiru Rooklord". Since both Banish, "Burial from a Different Dimension" and "Return from the Different Dimension" can be very useful.
Finally, a few cards have the heavy cost of discarding a Spell Card from your hand (like "Summoner Monk", "Cursed Seal of the Forbidden Spell" and "Chiron the Mage"), but "Koa'ki Meiru" Decks can recycle the "Iron Core of Koa'ki Meiru" as long as they want to, making these much more consistent than any other Deck.
See also: Rock Stun.
Koa'ki Meiru "Anti-Meta" Beatdown