In the year 2254 the USS Enterprise spent a week at K-12 undergoing repairs after sustaining damage on its previous mission to Darrien 224. While at the station, Captain Pike took a shuttle to Earth after being informed his father was seriously ill. The Enterprise left the station later the same day after learning the message had been faked, and thus the captain was in trouble. (EV comic: "The Flat, Gold Forever")
In 2269, the Enterprise reported to K-12 for installation and testing of a new Starfleet cloaking device developed by Doctor Bendes Kettaract. Carol Marcus was en route to another post and spoke briefly there with James T. Kirk. During the tests, the Enterprise encountered two Romulan vessels commanded by Liviana Charvanek, who said they were trespassing no further into Federation space than Kirk had when he stole her cloaking device. Following the tests, the Enterprise returned to K-12 for minor repairs. Specialized personnel from Section 31 removed the device, which had not performed as expected. (TOS - Year Four comics: "The Enterprise Experiment, Part 1", "The Enterprise Experiment, Part 2")
Following several days of repairs at K-12, the Enterprise cleared moorings from the station with orders to head for Deep Space Station K-22 in the Lorenian system. (TOS - Year Four comic: "The Enterprise Experiment, Part 3")
In 2274, Captain Kadan of the USS Icarus and his non-corporeal crew had been driven insane while traversing the galactic barrier. The Enterprise was able to rescue Icarus before it destroyed Phaeton. Afterward, at K-12, the 100 Phaetonians were being cared for temporarily, until a ship came to take them to Elba II. (TOS comic: "Eclipse of Reason")
- EV comic: "The Flat, Gold Forever"
- TOS - Year Four comic: "The Enterprise Experiment, Part 1"
- TOS - Year Four comic: "The Enterprise Experiment, Part 2"
- TOS - Year Four comic: "The Enterprise Experiment, Part 3"
- TOS comic: "Eclipse of Reason"