As soon as you arrive on the central platform, spread some ink around the entire platform. The purpose of doing this is to ensure mobility around the platform and to evade Octostomp’s stomp attacks.
Do note that you can also use Seekers for the same purpose. Immediately after the boss battle starts, move sideways so as to evade Octostomp’s first stomp attack. After the boss lands, move behind its back and create a line of ink on it.
Splatoon Mighty Octostomp Boss Battle Tips
In order to defeat it, you need to attack the tentacle behind it. After absorbing sufficient damage, a shower of purple ink will ooze out from its back and you’ll automatically land on the ground and prepare for the second round.
The initiation of second round clears the entire platform of all ink. Therefore, the first thing you need to do is to spread some more ink using your Main Weapon and Sub Weapon while continuously evading boss’s attacks.
Once you’ve spread enough ink on the platform, use the same strategy as above to bring it down. Trigger another purple shower of ink and prepare for the third and last round.
The third round is not much different from the first two rounds. But in the third round, the boss’s side consists of moving panels.
It’s not hard to ink these panels, but swimming through them can be a tad tricky. You can either wait for them to align in a straight line or move up in a zigzag fashion. Once again, target the writhing tentacle behind it to complete the battle.