Commander Tartar

The Telephone, also known as Commander Tartar, is the main antagonist in Octo Expansion.

Appearance and traits
In its telephone form, it appears as an old-timey telephone box. It frequently uses slang, but also has error messages inside brackets appear in its speech. Once Agent 8 has collected all 4 of the thangs, it connects its telephone body to the thangs, transforming itself into a blender. During the final boss battle, it appears as the telephone box with turquoise ooze seeping out, as well as an Octarian tentacle poking out and no longer speaks in slang or error messages.

Octo Expansion
The Telephone initially appears as an ancient-looking public telephone in the Deepsea Metro. It provides Agent 8 with two items:
 * 1) The CQ-80, a device through which they control which Deepsea Metro to go to next.
 * 2) The CQ Card, which holds the CQ Points used to enter missions and revive if failing.

The Telephone then tells Agent 8 about the promised land that awaits them outside of the Deepsea Metro, and informs them that they must collect 4 Thangs in order to return. Upon gathering all 4 Thangs, however, they actually form a massive blender. The Telephone then tries to grind up Agent 8 and Cap'n Cuttlefish into raw materials, only to be stopped by Agent 3, with the Telephone seemingly broken.

During a lengthy escape, the Telephone attacks Cap'n and Agent 3, eventually brainwashing the latter into tying up Cap'n and attacking Agent 8. Their brainwashing is broken when Agent 3 is defeated by Agent 8.

Following the defeat and Agent 8's escape above the surface, a gigantic stone statue emerges. In the hollowed out eye of the statue, the telephone appears and introduces itself as Commander Tartar and declares its intent to eradicate and recreate all life on Earth. The Commander activates a weapon from the statue's mouth; a massive cannon that threatens to destroy the entire world if fully charged.

Agent 8 manages to put a stop to it by inking the entire surface (with the assistance of Marina's Hyperbombs), blocking off the statue's source of power: sunlight. Despite this, the cannon is still able to fire, but is stopped by Pearl's voice-enhanced Killer Wail, with Tartar destroyed along with the statue.

Backstory
Commander Tartar is an AI created by a human scientist referred to only as "the professor" 12,000 years before the events of Splatoon 2. Its purpose was to pass down all of humanity's knowledge to the next capable species.

Commander Tartar initially saw hope in the Inklings and Octarians, but eventually became repulsed by their evolution, needless wars, and fashion obsession, ultimately concluding that they were unfit for its knowledge and reprogramming itself to create a new form of life that would be worthy of its patronage, while annihilating the existing lifeforms on Earth. The Sanitized Octarians are its creations, spawned from the biomass it has collected from the remains of its previous test subjects and refined into "the perfect life".

Trivia

 * Commander Tartar's name is a reference to tartar sauce, a sauce made using mainly mayonnaise, which may again reference the ooze seeping out of it. Tartar sauce is primarily used for seafood, referencing its displeasure for the evolved sea creatures and desire to annihilate them.
 * Tartar's name could also be a reference to Tartarus, a deep abyss far in the underworld in Greek mythology. It would reference how the facility is deep underwater. This may also tie into the possibility that the NILS Statue is meant to resemble the Greek god Hermes.
 * There is a similar looking telephone in Octo Canyon hanging to the side of the cabin in Tentakeel Outpost, showing signs of having rust being in a turquoise color.
 * It is possible that the "professor" Tartar refers to could have also been Judd's owner.

Names in other languages
Telephone

Tartar