The Boss Kettle for this mission can be found in the back of the Beaker's Lookout. To reach it, use a Grapellink in the back of the area to get to a Ride Rail. The ride rail will loop around the platform with the Kettle. Hit either of 2 Grapellinks to reach the kettle.
The Octostomp has not changed that much since the last game, however it does have some new tricks up its sleeves. The Octostomp will slide at the player before "stomping" and does not lose panels unlike the battle in Splatoon. During the 2nd phase, the Octostomp will wear a coat made of ink-proof material, much like the inside of a Hot/Cold shopping bag. The coat has a design of a penguin on the back, and holding it onto the boss is a large plastic buckle, which the player will need to shoot first before they can climb up. The Octostomp also is hiding an Octotrooper inside the top of the coat, complete with a Splatling gun. During the 3rd phase of the fight, the Octostomp gains another coat similar to the first one, but this one has two zippers at the sides, allowing its 2 extra faces to be revealed. At the back of the boss is the hole where the tentacle is resting, which the player will need to shoot in order to defeat the boss.
Phase 1[edit]
The Octostomp will run up to you and try to face plant itself on you, exactly as it did in The Mighty Octostomp!. You can climb up it once its on the ground, but it won't stay like that forever. The boss can also do a sliding charge attack. After the charge, the Octostomp will do its face plant.
Phase 2[edit]
And I brought this sweet new coat!
Neo Octostomp—intro to phase two, the Neo Octostomp.
The boss is now covered in armor that makes it un-inkable. To get rid of the armor, you must attack the black buckle holding the armor together. Its located on the Octostomp's face. If the boss still has its armor, it can do a attack where it fires a Splatling at you. It will use all of its attack methods from phase 1.
Phase 3[edit]
The boss regenerates its armor, and now it has two extra faces. These faces will make the Octostomp's sliding charge and face plant over a much wider area than before. The rush of air pushes the extra faces up during the slide attack which, by submerging yourself in ink, you can avoid. Destroying the armor will also get rid of the faces. It uses all attack methods from the previous phases.
Or you can drop off the main stage onto a road as the Octostomp can't reach you there. Then paint up it for the first phase, and for the second and third phases wait till it gets up to damage the buckle and the paint up it again. You should probably only do this if you are having trouble with the normal way to do the fight. It also takes a long time if you do it this way.