Octarian

The Octarians are a race of octopus creatures and the main antagonistic species of the story mode in Splatoon. They reside in Octo Valley and Octo Canyon, and are responsible for stealing Zapfish from Inkopolis. Their main ink color is purple/magenta. At one point the Octarians were a neutral species coexisting with Inklings, but this ended as result of conflicting interests of territory that lead to the beginning of the Great Turf War (in which the Octarians lost).

Unlike Inklings, the species includes a great amount of sub-species that act differently from each other. Like Inklings, certain Octarians can switch between mollusk form and humanoid form at will.

Known Octarians

 * DJ Octavio (Leader)
 * Marina (Octoling, member of Off the Hook, and Show Host)
 * Agent 8 (Octoling)
 * Dedf1sh (Sanitized Octoling)
 * The DJ of SashiMori (Octoling)

Types of Octarians

 * Octotrooper
 * Shielded Octotrooper
 * Octodiver
 * Twintacle Octotrooper
 * Shielded Twintacle Octotrooper
 * Deluxe Twintacle Octotrooper
 * Twintacle Octodiver
 * Octocopter
 * Deluxe Octocopter
 * Octoball
 * Octosniper
 * Octobomber
 * Deluxe Octobomber
 * Octostamp
 * Octostriker
 * Octohurler
 * Octoseeker
 * Octozeppelin
 * Octomissile
 * Octoling
 * Tentakook
 * Octocommander
 * Octoballer
 * Sanitized Octarian
 * Sanitized Octoling
 * Missile Octocopter
 * Speedy Missile Octocopter

Machines

 * Squee-G
 * Industrial Squee-G
 * Flooder
 * Octopod
 * Octorpedoes
 * Octostamp DX
 * Ink Piston
 * Octowasher

Great Octoweapons

 * The Octostomp
 * The Octonozzle
 * The Octowhirl
 * The Octomaw
 * The Octobot King

Octobosses

 * Octo Oven
 * Octo Oven XXL
 * Octo Samurai
 * Revenge of the Octo Samurai
 * Neo Octostomp
 * Octostomp Redux
 * Octo Shower
 * Octo Shower Supreme

In the manga series
In the end of the fan-made issue of Splatoon, a then unnamed Glasses-Kun flies over a bunch of Octotroopers and Octoballs. They appear again in the Hero Mode issues, when Glasses and Rider are enlisted by Captain Cuttlefish to recapture the Great Zapfish.

Trivia

 * According to the first artbook, Octarians aren't able to reproduce on their own and are thus created by cutting off a tentacle from a host. Their intelligence and rank is linked to how many limbs they possess, with high-class Octarians possessing more limbs than lower-class ones. However, it is not entirely clear whether this lack of sexual reproductive organs applies only to the lower-rank troops in the Octarian army or to the player and enemy Octolings as well. Based upon the fact that DJ Octavio is capable of creating sentient Octarians by severing his own tentacles, it is possible that other Octolings may possess the same ability. Some of these sentient tentacles, such as the Octo Samurai, have been shown to take on more definite humanoid form similar to that of the Octolings, but whether this is in fact the same or even the sole process by which the Octoling class itself originates is still debated among fans.
 * Worth noting also is the presence of Sashimori’s DJ, a ten-year-old Octoling. He possesses all eight tentacles and resembles an analogous phase in an Inkling’s own growth cycle, implying that Octolings and Inklings may share similar reproductive cycles. It should be remembered though that the exact reproductive processes of the Inklings themselves has not been explicitly detailed by official sources.
 * The bassist of the Chirpy Chips is an octopus, but has never been connected to Octarians and bears little resemblance to Octarians seen so far.
 * Some characters use slurs to refer to enemy Octarians, such as Marie repeatedly calling them for "Octoslobs" in the Octo Canyon campaign, Cap'n Cuttlefish calling them for "Octojerks" in Octo Valley, and Pearl once calling Sanitized Octarians for "Octo-nerds" in Octo Expansion.