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, better known by her pseudonym Dedf1sh, is a musician in Splatoon 2 whose songs appear in the Octo Expansion. Once a normal Octoling, she entered the Deepsea Metro's underground test facility and became sanitized, losing her free will. She re-appears as a full-fledged character within Splatoon 3's DLC Campaign, Side Order, in which she appears 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).

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

Side Order
In Side Order, Acht made her first physical appearance and can be seen in an elevator on the Spire of Order. She appears to have a laid-back personality and speaks in a somewhat monotone manner. She mentions having a connection to Marina, stating the two go "way back".

Trivia

 * In her 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.
 * Oddly, her 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 (in other words, taking the average of the remaining numbers plus an extra 0 to represent Splattack! (Octo)), the result is eight, the recurring theme of 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.
 * Paul of SashiMori bears some resemblance to her, with both having the same skull or octopus icon on their headgear and wearing black tops. It's unknown whether this means something or not.
 * In, Acht's signature can be seen on the exterior of Hotlantis.
 * The Octoplush song #35 caught follows the same naming convention as Acht's numbered songs.

Etymology
Acht is German and Dutch for "eight".

Dedf1sh is a portmanteau of "dead" and "fish", in reference to her 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 her song titles.