For veteran Yugioh players confronted with the game’s occasional disparity in power, there’s one anecdote that seems oft-repeated: “An FTK won Worlds”. Yes, in 2010 a literal first turn kill strategy, built around the Aqua-type Frogs took the highest accolade in the game’s history, intending to play the least amount of Yugioh possible in order to secure a victory. The year is now 2026, and a brand-new Aqua monster has been released, threatening to turn an already-excellent strategy into one which mimics that fabled 2010 list: Mercurium the Living Quicksilver. If you squint, this is a Rank 10 Lavalval Chain, a card which is banned, or perhaps a more recent comparison is Beatrice, Lady of the Eternal…which is also banned. Oh boy. This TCG-Exclusive has been turning heads with brand-new Trains on the horizon, but it might just arrive to tournaments ahead of schedule in a new variant of K9 Mitsurugi, which uses a suite of Insects to secure a first turn kill. Presenting K9 Mitsurugi FTK.
K9 Mitsurugi was one of the top decks of the previous format, winning a number of Regionals, and even a couple YCSes, so why the sudden tilt towards an FTK? Well, part of that choice comes down to a lack of opportunity cost, with the strategy already having a fair bit of room in its Extra Deck to slot in the necessary components. Second, the opening of a Chaotic Elements and Ame No Habakiri no Mitsurugi—or any way to find those two cards—can instead now result in a straight up win, rather than just a strong endboard. Turns out, not even giving your opponent the chance to play is far better than testing their mettle in a real Duel. At its core, this is a deck playing 4 bad cards, being 3 copies of Baby Spider and 1 Shadowpriestess of Ohm, and 3 lukewarm cards, in 3 Mother Spider Splitter. Beyond these questionable inclusions, outside of the deck’s context, you just have a strong and fairly standard lineup of K9 Mitsurugi packages. You’ll still be slamming K9-17 “Ripper” turn 0, and wiping boards with Ame no Murakumo no Mitsurugi, just with an added threat if your opponent opens 1 or fewer handtraps. Not a bad trade-off, if you ask me.
This is largely because Mother Splitter Spider, absent its role with Mercurium, is just…quietly fantastic in K9. It’s 3 Level 5 material, searchable with Seventh Tachyon, and if you don’t control monsters it’s a free Special. I’m honestly shocked we haven’t seen some form of Insect K9 experimented with before this! The Xyz lock isn’t even especially harsh, and there’s worthwhile Rank 5s & 10s both accessible via the Baby Spiders. Your bread and butter, though, remains Mercurium—at worst, it’s Abyss Dweller (Another banned card) for DARK monsters, but you can optionally also lock out the GY effects of FIRE, WIND, & EARTH monsters via its attach effect.
The main use case for the attach though, is finding Shadowpriestess. You’ll have Tributed 1 Baby to make the others Level 10s, meaning once you have Shadowpriestess attached to Mercurium, you can use its GY effect to detach Ohm and Special Summon it from the GY…beginning the cascade necessary to reach an endgame.
Let’s cover the combo in parts, because what you’re ultimately trying to do is access some component of the Mitsurugi engine, and Mother Splitter, to push for an FTK. The Mitsurugi Rituals are Level 8, and used to make Divine Golden Shadow Dragon Dragluxion, which does two big things: Find a Seventh Tachyon, and turn into Number 97: Draglubion. Tachyon is incredible for us, not just finding Mother Splitter by revealing Number C104: Umbral Horror Masquerade, but also any K9 monster if we already have access, giving it redundancy. Moreover, it requires us to place a card from our hand on top of the Deck—normally a downside, but here a means of ensuring 3 Baby Spiders are in our Deck. Turning into Dragluxion, and attaching Hope Harbinger, means Draglubion can Special Summon the only other DARK target, Number 92: Heart-eartH Dragon, representing 1600 damage via Shadowpriestess. All of these components work wonderfully together, with Jokul being able to Special Mother Splitter if we already have monsters, or make Jacks if we need a Rank 5 DARK K9 Xyz. Between Prayers, Tachyon, and Chaotic Elements (and potentially more), we have about a quarter of the deck dedicated to putting together the pieces for this win.
Even if you’re not literally killing your opponent on the first turn, this deck’s no slouch. We already talked about the power of Mercurium, but what if I told you it can attach Mitsurugi no Mikoto, Aramasa from Deck, detach and Special it, to kickstart your Mitsurugi line? Even if you aren’t set up to FTK, Mother Splitter gets you into either line, as Jokul is also conveniently a DARK monster. If you don’t need Mercurium though, why not make another DARK Rank 10: Varudras, the Final Bringer of the End Times? It’s an omni-negate and potentially multiple pops on its own, so again…if you’re stopped from literally FTKing, you can still functionally do so from multiple positions.
As I’ve illustrated, Mercurium is full K9 Combo, full Mitsurugi combo, or a literal FTK. This card is not okay, and the only reason people haven’t fully freaked out about it is due to the fact that it’s a TCG-Exclusive! There’s been no testing to show its power in the OCG, but the entire package absent K9s and Mitsus is under $10 at the moment. Buy it before the jump!
Now then, onto the actual combo. When you see a denomination like -800, counting up, that’s the total damage possible via Shadowpriestess at a given combo link.
Starting from Habakiri+Jokul, or ways to find them: Habakiri for Saji, Saji for Ritual, Ritual send Kusanagi+Aramasa for Habakiri, get back Ritual, Search Futsu. Ritual for Murakumo, Tribute Futsu in hand, add Mirror, Mirror for Futsu Tributing Habakiri, add any Mitsurugi. Xyz Summon Dragluxion and add Tachyon, adding Mother and putting back a card (such as the spare Mitsurugi from Habakiri’s search). Jokul to Summon itself and Mother, add Lantern, and Tribute Mother for 3 Babys, Tributing 1 to make the others Level 10. Mercurium, attach Shadowpriestess, detach and Summon via Baby in GY. -800 Tribute Mercurium, -1600 Tribute Jokul, Lantern Summon it back, add Case, Tribute Jokul+Lantern for -3200, Case to add Noroi, NS Noroi to Special Izuna, sending Lupis. Make Ripper to add Izuna, then Dragluxion for Draglubion, and Tribute the Murakumo twice for -5800, adding Prayers. Prayers for Futsu, Tribute for -6600, Draglubion for Heart-eartH, Tribute it, Draglubion, Shadowpriestess for -8000. If you already used Prayers earlier that turn, make Jacks instead of Ripper for another -800.
So the above is concerning, because the only indisputably bad part of it was needing to actually play Shadowpriestess; there’s good reason to include a Mother Spider package in K9, frankly. If you want a slightly more nuanced going-first gameplan than Shadowpriestess for games 2 & 3, Pharonic Advent is what you’re after. Once Special Summoned with the GY effect of Baby, it can Tribute 1 Reptile monster to add…any Continuous Trap from Deck to hand. You know, like the Limited Anti-Spell Fragrance, or Gozen Match, which can singlehandedly win the game. Yes, your mainline combo can search fundamentally ‘unsearchable’ cards, and it isn’t even very hard. You can even get the search from that errant Murakumo normally Tributed twice to Shadowpriestess, for a Prayers on the opponent’s turn! Beyond that, I quite like Fantastical Dragon Phantazmay in the Side, as a way to insulate your combo and put back redundant Baby Spiders.
The thing is, you don’t even need to open Jokul if you have Mother Splitter before you control a monster; you can just end on the normal K9 Mitsu endboard plus a Mercurium locking out DARK, which isn’t too shabby! There’s not a lot of decks which genuinely scare me, as a player, but this is one—FTKs are fundamentally unfun, but high risk, as if you’re interrupted you usually just lose. That’s why Gimmick Puppet, though annoying, was never the best deck in the game. Here though, your worst-case scenario if interrupted is uh, playing the best two engines in the format anyway? That’s a real concern, and as I said, beyond some of the spice this doesn’t look very far off of the previous format’s K9 Mitsu line-up. Yes, the limiting of both Jokul and Habakiri was warranted, and helpful in reducing this deck’s consistency, but it’s still plenty available with the 9ish strict ROTA effects we have, or 10 if you count Seventh Ascension. Just as long as you manage your locks appropriately, nothing is limited for you, from the deck. The real strength of Mitsurugi is that it’s agnostic to any specific Extra Deck summon type.
We aren’t even on as large of a Rank 5 package as we could have been, as there’s worlds where K9 allows us to splash for N.As.H. Knight to make a live C104. The Extra is quite tight already, so I opted instead to play a few Links if things get hairy, but with a deck that’s occasionally feast or famine, it may be the sensible thing to lean into the strength we have when undeterred. That said…that strength should be an FTK, so who’s really to say?
How does this list make you feel? Is there something else heinous that Mercurium enables, now that he’s debuted in the TCG? What else in Burst Protocol do you want to see me cover? Should K9 and/or Mitsurugi have been hit harder on the banlist? Let me know in the comments below!
