Octo Expansion

"Pale summer moonlight shimmers on the seafloor. An octopus, unaware that dawn will bring capture, Rests within a trap, dreaming fleeting dreams..."

- The opening poem of the Octo Expansion.

Splatoon 2: Octo Expansion is paid downloadable content for Splatoon 2. It was revealed during the 2018-03-08 Nintendo Direct and was released on 2018-06-14 at July 27, 2024 with Version. A physical version of Splatoon 2 with the DLC built in was exclusively released in Japan on 2021-10-08. On 2022-04-22, the Octo Expansion was also added to Nintendo Switch Online + Expansion Pack.

The mode is located at the subway entrance in the alleyway to the upper right of the map. It is also referred to as the Deepsea Metro on the drop-down map.

Story
The player takes the role of Agent 8, an Octoling with amnesia who finds themselves in a strange subway station connected to a series of research facilities deep underground. As the game starts, the Octoling sees Cap'n Cuttlefish ready to attack them before stopping, seeing that they do not have a weapon with them. Cuttlefish then informs the Octoling that they and Agent 3 fought in Octo Valley before "someone" attacked them and caused the Octoling to lose all of their memories in the process. He then asks if they remember anything, which prompts the customization of the player's Octoling. After finding a way through the beginning of the subway, Agent 8 and Cap'n Cuttlefish come across an empty platform with a telephone ringing. As the Octoling answers the Telephone, (aka Commander Tartar). It identifies them as Applicant No. 10008; deeming the name too long, Cap'n Cuttlefish decides to give them the name "Agent 8" for short. The Telephone tells Agent 8 that they would want to go to the "Promised Land" so they can be free, but to do so, they must collect four "thangs". As the call ends, a train pulls up towards Agent 8 and Cap'n Cuttlefish and stops for them. They then meet C.Q. Cumber, the conductor of the train, who explains the functions of the CQ-80 and the CQ Points system. Shortly afterwards, Pearl and Marina make contact with the two of them and offer their help in escaping.

After collecting all four "thangs", the telephone cryptically asks whether Agent 8 is "ready to ascend to a higher plane of existence" and "willing to become something greater than yourself", before using the thangs to seemingly open a door out of the Metro. It is soon revealed to be a trap, however, Pearl and Marina realize the thangs were parts for a giant blender that the Telephone planned to use to render them into raw material.

Before the blender can turn on, Marina activates a distress signal from Agent 8's CQ-80, prompting Agent 3 to smash through the ceiling and destroy the blender. Agent 3 is knocked out, but Agent 8 can use their employee-model CQ-80 to activate an elevator to the surface. After a lengthy escape, Agent 8 is forced to defeat a partially sanitized Agent 3, who had been attacked while they were escaping. Once on the surface, Pearl and Marina prepare to airlift Cap'n Cuttlefish and Agent 8 to safety, but the above-ground section of the facility proceeds to rise from the ground, now revealed to be part of a human statue. The Telephone introduces itself as Commander Tartar, an AI created 12,000 years ago to pass on human knowledge to any species worthy enough. It reveals that it has judged both Inklings and Octarians as unworthy of receiving its knowledge and begins activating a weapon to destroy and recreate life on Earth, fueled by the raw material of the successful test subjects that it seeks to use to create "perfect" life. Marina, Pearl, and Agent 8 hurriedly put a stop to the statue, using Marina's prototype hyperbombs and the Princess Cannon, powered by Pearl's loud voice. With the world saved and Tartar destroyed, Pearl and Marina hug with Cap'n Cuttlefish celebrating and Agent 3 wakes up. Agent 8 watches and smiles at them, finally able to be free. The group then look out to Inkopolis, Cap'n Cuttlefish presses the CQ-80 and the staff credits play. After the credits begin to finish, Agent 8 looks back at the player and smiles at them. With the world saved, Off the Hook returns to Inkopolis Square, dropping off Agent 8 there as well.

When Agent 8 returns to the Deepsea Metro, C.Q. Cumber tells them that they can now transfer credits into items as well as find mem medals in different Stations that can be used to exchange items in the Vending Machine. Cap'n Cuttlefish informs Agent 8 that Agent 3 went out on patrol, and he wished to check on the denizens of the deep for a while longer.

After Agent 8 completes all the tests, a locker in the Central Station will open and Agent 8 will have a battle with their "Inner Agent 3" using the classic ink colors of blue and orange respectively. Defeating them will reward the player with the Golden Toothpick, a headgear item equitable in multiplayer battles.

Gameplay
The Octo Expansion adds a new single-player campaign consisting of eighty levels. Off the Hook supports Agent 8 from above ground and their help can be used to skip missions that are too difficult.

The first station has the Telephone, where Agent 8 learns the details on how to escape the Deepsea Metro. The Telephone also provides Agent 8 with the CQ-80 device (a flat controller shaped like a submarine), used to navigate the underground; and a CQ Card, which is used to store CQ Points. C.Q. Cumber will issue an initial 1000 CQ Points to start.

Entering each mission costs a set amount of points, for either one, three, or five lives. The player can then choose between multiple challenges, each with a different weapon set. Depending on the weapon set chosen, a different amount of points is awarded (harder sets provide bigger rewards). Players enter the actual level by pressing at the turnstyle.

Lives are lost not only from being splatted but also by failing to comply with certain test conditions. If the player fails to complete the test's conditions to pass, an inflatable balloon of ink attached to Agent 8's ink tank will explode and splat them in the process.

If the player loses all of their lives, they may continue from the last checkpoint with all lives returned by paying more points, return to the station for free (but still having to pay to re-enter the level), abandon the level and return to the subway, or ask for help from Off the Hook to skip the level. Off the Hook can only help Agent 8 skip a level if they fail at least twice. When prompted to ask for help, it requires the regular fee to auto-pass the level, wherein Marina hacks into Kamabo's mainframe to trick it into thinking Agent 8 passed. The resulting mem cake will be gray, with only the quote "Your guess is as good as mine." However, if pressed to ask for help, the player can press X to "Tough it Out" and continue to play the level as normal. If skipped, the mem cake of that level will not be collected, barring players from certain rewards until they have completed the station properly.

If a player finds themselves with less than 100 CQ Points after losing all of their lives, a game over screen will appear instead of a continue screen. The player will then return to the Metro, where Pearl will take money from her father and Marina will convert it into CQ points, transferring 3000 CQ Points to Agent 8. However, the player will be in debt, which can be repaid through Cap'n Cuttlefish. Players cannot access the secret boss fight if they have debt.

The normal Octarians from Octo Canyon are replaced with Sanitized Octarians, which are a distinctive shade of sickly green. Enemy Octolings can use more main weapons and special weapons, previously only seen in online multiplayer modes. For example, in the first test, an enemy Octoling can use an Inkjet. A select number of levels are also special only, meaning Agent 8's special bar never goes down.

Some tests have Agent 8 go against a team of four Sanitized Octolings, in the style of ranked modes. The time limit is always five minutes and Agent 8 has unlimited lives until the time limit ends.

After completing the story, players can play as a male or female Octoling in multiplayer gameplay and customize them just like Inklings. Gear and weapons will be shared between the characters in the same account.

A short gameplay video of one of the missions was published on 2018-04-30. It shows a female Agent 8 on a mission requiring her to defeat a set of Sanitized Octotroopers, Octosnipers and Octocommanders within two minutes. This video also marks the first appearance of canisters similar to the special weapon canisters from Octo Canyon, as well as metallic briefcases. Both are marked with the same logo as the CQ-80 and the CQ Card, unlike the Octo Canyon canisters that show the Ammo Knights logo.

The objectives of the missions were revealed in a short gameplay video of Stamped-Up Station. It is a set of three floating pieces of a goal that must be covered in ink to be activated and be touched for the level to be completed. There are also smaller posts that emit red beacons that function the same as Mini Zapfish.

After three of the thangs are found, Cap'n Cuttlefish will decide to make a "missing" poster for Agent 3, asking Agent 8 what they look like. This determines Agent 3's gender, skin color, and eye color.

During the escape, if Agent 8 dies five times in a phase, their "Skip Charge" will be filled and will be allowed to skip the phase. If so, the sounds of a Splashdown and a Sting Ray can be heard and there will be a simple transitional phrase on the screen, stating that Agent 8 got past the phase. In the final boss, it will be instantly filled after one failed attempt.

When Agent 8 returns to the Deepsea Metro, they will be able to use the vending machine in Central Station to exchange 15,000 credits for an item and go around other stations to claim mem medals to be exchanged for the vending machine. The vending machine has more variety than the Ammo Knights Enhancifier, having the chance of getting more than one drink ticket, upgraded food tickets, cash, ability chunks, and credits. The items range from getting every type of drink ticket to even getting tens of thousands in cash.

Completing all missions with each challenge cleared and defeating the secret boss will change the background of the CQ-80 to one featuring the Kamabo Corporation logo and a stamp with the Inkling text saying "COMPLETE" on the bottom of the map.

Stations
There is a mandatory tutorial station, Abandoned Station.

If a station has dual IDs, the later letter in alphabetical order takes precedence, as inferred by the cost of its test fee and the way two lines overlap each other. Stations with double circles denote where thangs are. Line A is the only line that has a station with 00 as its number, the Central Station.

Rewards
Upon completing the Octo Expansion, the player is rewarded with playable Octolings and an Octo Shot Replica to use in online battles.

Gear
Purchasing the Octo Expansion unlocks the Studio Octophones and the Octo Layered LS. As soon as the player enters the game and finishes Inkopolis News, a box containing both pieces of gear will be in the center of the Square.

Fourteen gear items are obtainable through the Octo Expansion. All players will see the items in-game, but only players who purchase the Octo Expansion will be able to obtain the items for themselves.

Of all the items listed here, only the Golden Toothpick requires the player to pass all stages without help from Off the Hook.

Music
The full version of the Octo Expansion trailer song, called Nasty Majesty, was performed during Off the Hook's live concert at NicoNico Chokaigi 2018.

On 2018-05-21, a new character was revealed, a Sanitized Octoling DJ called Dedf1sh. According to Nintendo, Dedf1sh was a DJ with a promising future in the music world. During her search for inspiration, she came across a deep-sea testing facility and became sanitized. Despite this, she kept up her career as a DJ, and her music is heard throughout the facility.

Manga adaptations
The Splatoon manga adapted the Octo Expansion into the Octo arc. It lasted from chapters 24 to 28.

In the Octo arc, Goggles wakes up in the Deepsea Metro, after being washed away during his "part-time job". He is greeted by Eight, who saves him from some Sanitized Octarians. He meets up with Cap'n Cuttlefish.

Trivia

 * Most of the station titles and subtitles are references to '80s and '90s pop culture.
 * Many stages on the Deepsea Metro map are references to popular movies and songs; mainly hip-hop and rap.
 * The Expansion costs $19.99 (Excluding tax) in the US, €19.99 in the EU, £17.99 (Including VAT) in the UK, and ¥1800 (Excluding tax) in Japan. It is the first paid downloadable content announced for any game in the Splatoon series.
 * The Studio Octophones and Octo Layered LS were available early by pre-purchasing the Octo Expansion. This is a throwback to the initial Splatoon Global Testfire, where players who pre-purchased Splatoon during the event were given the Studio Headphones and a special squid-themed layered shirt.
 * The various phases during the escape are named after internal human body parts and are also placed roughly where the parts are situated in a human body. These places are revealed to be inside the NILS Statue, which resembles a human being.
 * The number eight is a recurring theme throughout the expansion. For example:
 * Splatoon 2: Octo Expansion is eight syllables long.
 * The DLC has an overall 80's theme, with the stages featuring iconic items from the time period such as unraveled cassette tapes and snapping popsicles to name a couple.
 * Agent 8 (subject No. 10008) is the main protagonist.
 * The CQ-80 device is used to navigate Deepsea Metro.
 * Octo Expansion has exactly eighty levels.
 * The tubes on the sides of the checkpoints resemble the number eight.
 * Each line of the poems on the mem cakes has exactly eight syllables.
 * Some levels require the player to push an 8-Ball to a goal.
 * Track #8 regret plays during these levels.
 * Some levels require the player to collect eight data-points.
 * If the player goes through the lines in alphabetical order, the last thang is on the eighth line.
 * The escape has eight phases if the final boss fight is counted.
 * After the final boss fight, when Pearl uses the Princess Cannon against the NILS Statue, the turf covered for the "Good Guys" goes up to 888.8%.
 * The five music tracks from the Octo Expansion are numbered from 80 to 84 in Squid Beatz 2.
 * The locker that has Agent 8's memories in it, which are used to enter the secret boss fight, is locker #8.
 * In the Diaphragm Phase of the escape, eight locks need to be unlocked to get to the energy core.
 * The Squid Bumpers that appear at the entrances to the missions have eight stubs at the base, as opposed to the squid dummies in the Shooting Range which have ten.
 * The music files in Marina's chat room are saved as 'mp8' files.
 * There are eight main characters: Agent 3, Agent 8, Pearl, Marina, Cap'n Cuttlefish, C.Q. Cumber, Iso Padre and Commander Tartar.
 * The DLC was announced on March 8th, 2018, and released in 2018.
 * There are eight Octo Expansion songs available for Squid Beatz 2 if amiibo rewards are counted.
 * The total cost of the DLC when combined with the base game is $79.98, or roughly $80 (in US dollars and excluding tax), although this is likely a coincidence.
 * Unlike Marie and Sheldon, Cap'n Cuttlefish and Off the Hook are aware of Agent 8 being splatted or failing tests, as they advise them when they respawn or react to them messing up, as well as having unique dialogue options when using different weapons.
 * The 8-Ball station subtitles are references to the sayings on Magic 8 Balls.
 * The visuals and audio allude to the vaporwave style, characterized by neon signs, glitchy art, 3D objects, statues, VHS videos (e.g. upon clearing a challenge or obtaining a thang), '90s web design (e.g. Marina's chat room), and sample-heavy music (mostly by Dedf1sh).
 * While Dedf1sh's songs are numbered, a few numbers appear to be skipped. These include numbers 3, 7, 10, 15, 17, and 18.
 * When the player is in the train, a version of Calamari Inkantation can be heard playing.
 * Outside the café Spyke is located in (near the Deepsea Metro's entrance), an employee model CQ-80 and two CQ cards can be seen.
 * Only 14 levels are strictly required to reach the end of the Octo Expansion (the four thang stations, the eight phases of the escape sequence, and Abandoned Station and Fake Plastic Station), but all routes that the player can take to reach the four thangs require at least two additional levels to be completed, so the minimum number of levels that must be completed to reach the ending is 16.
 * Some developers from The Legend of Zelda: Breath of the Wild helped with the Octo Expansion and there are many notable similarities between the two:
 * The Thangs are similar to the four Divine Beasts.
 * The player must fight through different areas to get to the final boss, similar to Hyrule Castle.
 * There is a traditional boss fight (Agent 3 and Ganon) and then the final boss where the player moves around quickly and shoots specific points (NILS Statue and Dark Beast Ganon) with the support of an ally (Marina and Princess Zelda) followed by a cutscene where an ally gives the final blow (Pearl and Princess Zelda).
 * Being able to retrieve lost memories of the main character.
 * Having a secret ending only seen if all memories are collected.