The Deepsea Metro

The Octo Expansion is Splatoon at its strangest and best. It takes the series' cheerful tone and drops it into a dark, quiet, faintly wrong underground where the rules of the surface do not apply. The setting is the Deepsea Metro, an aging subway system that runs through the ruins beneath Inkopolis, and its protagonist is an Octoling who has forgotten everything, including her own name.

Waking up

The expansion opens with the player's Octoling, soon dubbed Agent 8, regaining consciousness in the dark next to Cap'n Cuttlefish. Neither of them knows how they got there. Cuttlefish had been investigating something and lost the trail; Agent 8 remembers only a song, the Calamari Inkantation, and a vague sense that she had been trying to reach the surface when she was attacked.

The only way out is through. A talking telephone, the mouthpiece of an entity that calls itself Commander Tartar, offers a deal: complete the metro's tests, collect four "thangs," assemble them, and be granted passage to the "promised land." Cuttlefish, who has never trusted a talking phone in his life, comes along anyway. So does a support team on the surface: Pearl and Marina of Off the Hook, who pick up the Cap'n's radio signal and start feeding Agent 8 tips, jokes, and Marina's hacking.

Riding the line

The Deepsea Metro is a real subway, complete with a route map, stations, and a conductor. That conductor is C.Q. Cumber, a sea cucumber in a train driver's cap who is polite, precise, and utterly committed to the rules. Each station is a test: a small level with a specific objective, a specific weapon, and a fee in CQ points. Fail, and C.Q. Cumber splats you instantly and lets you try again. It is the most demanding platforming the series has offered, and it is presented with the bureaucratic calm of a commuter rail.

The other passengers are the expansion's secret heart. The train is full of sea creatures riding in silence, and one of them, a giant isopod called Iso Padre, becomes Agent 8's confidant. He collects mem cakes, small edible sculptures that turn out to be fragments of Agent 8's lost memories, and each one is captioned with a haiku-like poem about her past. Piecing them together reveals a girl who loved music, fought for the Octarian army, and left.

Kamabo Co.

The tests are run by Kamabo Co., a corporation whose branding is everywhere and whose purpose is never quite explained until the end. Sanitized Octarians, gray-skinned soldiers stripped of their will, patrol the stations. The whole system has the feel of a factory processing "test subjects," and the mem cakes make it clear Agent 8 is not the first.

Fans theorize that Kamabo's facilities are repurposed human infrastructure, and the surface-level ruins beneath Inkopolis (a highway, a subway, an enormous statue) support the idea. Whatever it was, Commander Tartar has been running it for a very long time.

Every station is a test. Every passenger is quiet. The only thing that talks is the phone.

The blender

The thangs, when assembled, form a giant blender. Agent 8 and Cuttlefish realize this a moment too late: Tartar's "promised land" was a euphemism for being liquefied. They are saved by Agent 3, the hero of the first game, who crashes into the facility and breaks the machine but is drenched in sanitizing ink in the process. The escape that follows, through the guts of the facility with a mind-controlled Agent 3 on their tail, is one of the series' hardest and most memorable sequences.

Once above ground, on the head of a colossal human statue rising out of the sea, the final confrontation unfolds. Tartar reveals its true purpose, Pearl and Marina fly in by helicopter, and the four of them stop the AI from wiping out life in the Inkopolis area. Agent 8 finally sees the sky.

The Octo Expansion gave Octolings to multiplayer, Agent 8 to the story, and Tartar to the lore. It also introduced Acht, the Octarian DJ later known as Dedf1sh, whose sanitized remixes score the tests and whose story Side Order would eventually finish. And it left the Deepsea Metro itself, still running somewhere under the city, its passengers still riding in silence toward a stop that never comes.