Spinal Phase

Spinal Phase is the seventh stage in Octo Expansion's finale.

Gameplay
Agent 8 must defeat a partially sanitized Agent 3 in a boss battle.

Agent 3 is armed with their Hero Shot, Splat Bombs, and has a large arsenal of Special weapons at their disposal. They will always enter the arena by a Super Jump and activate Splashdown upon landing. Additionally, Agent 3 can dodge roll at any time (as if they were equipped with Dualies), forcing Agent 8 to wait for Agent 3 to leave an opening in their attack patterns. Agent 3 will use the Hero Shot and Splat Bombs in all phases of the fight, but uses a single type of special exclusively in each phase. It should also be noted that like the player, Agent 3 is able to heal themselves by swimming in their own ink or performing a Splashdown.

Phase 1
Agent 3 will use the Baller to try and corner Agent 8 before setting it off; the Baller can be broken with sustained fire, leaving Agent 3 briefly vulnerable to attack.

Phase 2
After taking sufficient damage, Agent 3 will Super Jump back to the spawn point on the UFO flying over the arena, Super Jumping back down with a Splashdown to begin the next phase. Agent 3 will now use a Curling Bomb Launcher, and will continue to attack with it until the next phase.

Phase 3
Agent 3 will remain on top of the UFO, firing off the Sting Ray in between volleys of Hero Shot fire and Splat Bombs. The UFO is difficult to reach with the Octoshot's fire, but it is low enough to throw a Splat Bomb on top of it.

Phase 4
Agent 3 will now use the Splashdown up to three times in a row. As Agent 3 is fully healed each time they use a Splashdown, Agent 8 has to take them down quickly after the third Splashdown is performed.