This mission cannot be accessed physically in-game because it is a fictional mission. If real, it would be accessed by walking up the stairs that are located next the entrance of The Crater, which is located in Splatsville. Taking these stairs would reveal a Launchpad that would take you back to Octo Valley. The Kettle would be located right above the Octosniper Ramparts mission in Area 4.
Boss Appearance
Ashley
Ashley is the main boss of this mission, where she is partially sanitized. She retains her hairstyle and eyebrow features, but wears the Ink-Tinted Goggles, White Inky Rider, and Punk Whites. Her legwear changes to the "colored patterned leggings", her ink color becomes turquoise, and her eye color changes to the Cyan + Orange Ring option. She also has a piece of the sludge that Commander Tartar created in her goggles. Her weapon is the E-liter 4K Scope. She is guarded by three of the five Great Octoweapons.
Great Octoweapons
The Great Octoweapons that guard Ashley are the Octonozzle, the Octowhirl, and the Octomaw. They act as secondary bosses that must be defeated in order to splat Ashley. The Octonozzle has a different appearance. The seaweed around it is the same color, but its eyes have changed to match a Sanitized Octarian's eyes. Its shoes have changed from being purple to white. The Octowhirl has a slight change in appearance, that being every part of its body that was originally magenta is now turquoise. The Octomaw also has a slight change in appearance, that being its eye color changing from magenta to turquoise.
Gameplay
The three idol groups and playable agents fight during the three phases. The layout looks like this:
The boss fight takes place in an circular arena similar to the other boss fights in previous games. Directly to the right behind the Spawn point is a speaker that plays the disturbing boss screams found in Octo Valley and Octo Canyon. Despite the kettle being located in Octo Valley, the mission takes place in Splatsville because it is only accessible through Splatoon 3.
Phase 1
During phase 1, Ashley will be standing on top of a Sanitized Octonozzle. During the fight with the Octonozzle, Ashley will be attempting to splat you with her E-liter, and you'll have to restart at the checkpoint if you get splatted. The Octonozzle can be defeated in the same way in Octo Valley. The Octonozzle will have all its layers extended, so to defeat it, you have to shoot all of the tentacles from all three layers. Once all tentacles have been destroyed, the Octonozzle will explode, making Ashley fall, allowing you to splat her.
Phase 2
During phase 2, Ashley will be standing on top of a Sanitized Octowhirl. During the fight with the Octowhirl, Ashley will be attempting to splat you with her E-liter, but after being knocked off, she will place three Ink Mines as another defense. Like the Octonozzle, the Octowhirl can be defeated in the same way in Octo Valley. To defeat the Octowhirl, you have to get it completely submerged in your ink, which will make Ashley fall and reveal the tentacle. You then shoot the tentacle to destroy the Octowhirl, allowing you to splat Ashley.
Phase 3
During phase 3, Ashley will be standing on top of a Sanitized Octomaw. During the fight with the Octomaw, Ashley will be attempting to splat you with her E-liter, but after being knocked off, she will place a Wave Breaker as another defense. Like the Octonozzle and the Octowhirl, the Octomaw can be defeated in the same way in Octo Valley. The Octomaw will already have its gold teeth, so to defeat it, you need to knock down most of its teeth and throw either a Splat Bomb or Burst Bomb in its mouth. This will cause the Octomaw to swallow the bomb and explode, making Ashley fall and allowing you to splat her.
The mission name is a reference to the four thangs and Commander Tartar.
There are multiple reference to the number "three" in this boss fight:
The mission number is 33.
There are three phases.
The three idol groups from each of the three Splatoon games appear: Squid Sisters from Splatoon, Off the Hook from Splatoon 2, and Deep Cut from Splatoon 3.
The three playable agents also appear: Agent 3, Agent 4, and Agent 8.
There are three Great Octoweapons that guard Ashley: the Octonozzle, the Octowhirl, and the Octomaw.
In each of the three phases, three different songs can be heard.
Marie uses her Hero Charger to knock off Ashley's sanitized goggles in a similar way she knocked DJ Octavio's hypnoshades off of Callie in Bomb Rush Blush (mission).
Ashley doesn't lose consciousness after this, though it is unknown why that is.
There is no alternate dialog for repeating the mission, as it cannot be repeated.
Marina is the first character to refer Ashley by her nickname since Ashley left Inkopolis.
The location of the kettle being in Octo Valley is referencing how Ashley was originally born in Inkopolis Plaza.
After everyone has left, there is a very short conversation between Commander Tartar and Mr. Grizz.