Acht

"Everyone, meet Dedf1sh. Previously a promising, up and coming DJ, her pursuit of breakbeat perfection eventually led her to a subterranean test facility, where she was "sanitized." Though little of her former self remains, she continues crafting DJ delicacies, and the halls of the test facility echo with her bumping tracks to this very day."

- Live from the Squid Research Lab

Acht, also known by their stage name Dedf1sh, is a musician in whose songs can be heard around the facilities of the Deepsea Metro. Once a normal Octoling, they entered the Deepsea Metro's underground test facility and became sanitized, losing their free will. They make their first physical in-game appearance within DLC campaign,, in which they appear to assist Agent 8 and Pearl within the story.

Songs
Before the release of the Octo Expansion, a video titled "Catalog Mix" featuring short sections of some of Acht's songs was uploaded. The only Dedf1sh song that was named prior to Octotune release was Splattack! (Octo).

Appearance
Though Acht never makes a physical appearance in Octo Expansion, they can be seen using a turntable in their album artwork. They are a sanitized Octoling with a pale green skintone; unlike other sanitized Octolings, their ink color is a gradient of blue to red. The edges of their limbs are tinted bright red to black in a manner similar to Marina and Shiver. Shown only over the waist, they appear to wear a loose black shirt or dress that hangs over their left shoulder by a thin strap. They wear a pair of Octoling Shades as well as large, silver headphones atop a monochrome black and white baseball cap that features the same logo seen on Paul's hat. They additionally wear a cuff bracelet featuring a black to red gradient on their right wrist.

In Side Order, Acht makes their first physical appearance in the SS undefined. Their appearance in this mode highly resembles their previous artwork-exclusive appearance; they are revealed to wear a thigh-length dress with a slit on the left side with red lace-up stitching, as well as high-heeled knee-length laced black boots. The back of their hair is mostly shaved and features a tentacle in the center back, while the two sides have carvings resembling the katakana "ミ" and "ズ" from top to bottom on the left side and "タ" on the right side, spelling out their Japanese last name "ミズタ" (Mizuta). They additionally have new extensive bandaging on their left forearm and red-tinted glasses.

Splatoon 2: Octo Expansion
Unseen during the Octo Expansion, Acht is the producer of the music heard throughout Kamabo Co.'s facilities. Before their disappearance, Acht was a promising DJ who spent most of their days making and mixing songs. They had learned every genre of music, causing their music to be described as "mimetic". They are diligent and hardworking, but it is said that they had "doubts and conflicts about production" so they let themself be sanitized to devote themself to nothing but music. Due to their sanitization, they do not make music considering others, instead letting what comes out of their "inner self" take form.

Splatoon 3: Side Order
In Side Order, Acht can be seen in an elevator in the Spire of Order as Agent 8 and Pearl board it for the first time, offering to explain the way it works to them. They appear to have a laid-back personality and speaks in a somewhat monotone manner. They mention having a connection to Marina, stating the two go "way back".

Trivia

 * In their album art, Acht uses a series of turntables each with the number 8 on them and eight buttons, corresponding to an octopus' number of arms and the overall recurring number eight through the Octo Expansion.
 * The background of Acht's album art features the Kamabo Corporation logo, also seen in places such as the CQ card and C.Q. Cumber's hat.
 * Acht's numbered catalog of songs appears to be missing select numbers: 3, 7, 10, 15, 17, and 18.
 * When adding the numbers from the title of each song and then dividing the total by the number of songs Acht has composed, the result is eight, a recurring theme in the Octo Expansion.
 * Originally, the music in the Octo Expansion stations was planned to only be background music without a musician or any sort of backstory. After Seita Inoue ended up liking the music a lot, he created Acht to bring more attention to it.
 * The Octoplush song #35 caught follows the same naming convention as Acht's numbered songs.
 * In the Japanese trailer for Side Order, Acht uses ボク (boku) as their personal pronoun, which is usually a masculine pronoun, but is also used by tomboys and people who are non-gender conforming.

Etymology
Acht is German and Dutch for "eight". Acht also means "attention, heed".

Dedf1sh is a portmanteau of "dead" and "fish", in reference to their sanitization and no longer showing vital signs. The name is likely mimicry of the DJ and musician deadmau5 as both are stylized in leetspeak, which is a nod to computer hacking evidenced by the purposeful misspelling of "dead" and their song titles.