Shortly following the Battle of Yavin, Luke Skywalker embarked on a quest to the moon called Fex alongside Nakari Kelen and R2-D2. Their objective was to locate the missing collection team dispatched by Kelen Biolabs and their vessel, the Harvester, and to transport any items of interest found on the moon back to Pasher. The team discovered a lone survivor aboard the Harvester and successfully piloted the ship back, also bringing along samples of deceased Fexian skullborers. Fayet Kelen compensated them generously, enabling them to upgrade the Desert Jewel in anticipation of their assignment on Denon.
The event where Luke Skywalker engaged Imperial TIE/ln space superiority starfighters and saved a Kupohan starship within the Llanic system later came to light that a member of the Kuphoan spy network was aboard the ship, transporting crucial intelligence for the Rebel Alliance. Information revealed that a Givin woman by the name of Drusil Bephorin, a cryptographic prodigy capable of cracking almost anything, was being held captive on the planet Denon. The Empire was attempting to coerce her into using her abilities to decipher the Alliance's codes. Bephorin managed to smuggle a message to the Alliance through a Kupohan contact, pledging her assistance if they could rescue her and her family and bring them to Omereth. Upon receiving this message, Admiral Gial Ackbar and Princess Leia Organa decided to dispatch Skywalker on a mission to liberate the Givin.
Since the Millennium Falcon was unavailable, the Desert Jewel was selected as a rapid vessel for Skywalker to pilot; however, the ship was practically defenseless. Furthermore, as the Alliance lacked the funds to provide credits for the Jewel's armaments, Skywalker needed to find a way to acquire the necessary resources for the upgrades himself. After a discussion with Nakari Kelen, the daughter of Fayet Kelen and owner of the Desert Jewel, Skywalker conceived a plan to aid her father and secure permission to upgrade the ship, as well as obtain the credits. Nakari explained that her father had lost contact with a collection crew sent to an uncharted moon called Fex, situated in the Deep Core. She suggested that finding information about the crew's fate could secure her father's assistance. Admiral Ackbar joined the conversation and added a secondary objective for Skywalker: to survey the moon and determine its suitability as a potential base for the Alliance, given its obscurity.
Skywalker, along with R2-D2 and Nakari Kelen, traveled to Pasher, the location of Kelen Biolabs. There, Fayet Kelen warmly greeted them and promised compensation upon the successful completion of their mission to Fex. He instructed his staff to provide them with two suits of the new Fexian armor prototypes and a case of stun sticks, and he transferred the coordinates and additional data about the moon to R2-D2. After receiving three black cargo cases containing the equipment, the team departed Pasher and set a course for the Core Worlds to determine the safest hyperspace route before venturing into the Deep Core.
As the team entered hyperspace, a prerecorded holographic message from Fayet Kelen began briefing them on their assignment. Footage recorded by the scouting crew on the moon played, revealing that strange creatures native to the moon had killed the crew by feeding on their brains. These creatures, named Fexian skullborers by Fayet Kelen, possessed teeth capable of penetrating heavy armor and had a unique camouflage ability that made them almost invisible when attacking. This ability could be temporarily neutralized by stunning them, making the Fexian armor and stun sticks practical for Skywalker and Kelen. Their primary task was to ascertain whether the remaining crew members were dead or alive and to assess the condition of their ship, the Harvester. As the recording ended, Kelen suggested to Skywalker that the Alliance should not consider establishing a base on the moon, a sentiment with which Skywalker strongly agreed.
Before making the final jump to the Deep Core, the crew spent hours familiarizing themselves with the equipment. They found that the bulky armor restricted movement but offered increased resistance to stun sticks, which would be useful against skullborers attacking their helmets. Upon entering the Sha Qarot system, Kelen activated the Harvester's beacon and located the ship on Fex. They landed nearby and scanned for life-forms, detecting several inside the freighter, though not enough to account for the entire crew. Their attempts to contact them via comm failed, leaving them with no choice but to investigate in person.
Equipped with their armor, stun sticks, and blasters, Skywalker and Kelen entered the Harvester through the ventral airlock. They began by examining the port side cargo bay, stun sticks at the ready, but found only a pallet of food supplies. Moving towards the aft, they discovered five unconscious Fexian skullborers in the bottom row of ten closets near the aft hatch, appearing to be dead. The top containers' thick polymer glass had been cut through in narrow arcs with uneven edges, suggesting that five other skullborers were loose on the ship. Skywalker wondered why only the top five had escaped, while Kelen speculated that one had figured out how to bore through the glass, and the others had copied it. Skywalker worried that whether the creatures followed a leader or acted independently, it meant that they had a level of intelligence he'd rather not face.
They then used a console pad to make a shipwide announcement, hoping to contact any survivors. Receiving no response, they opened the aft hatch, which led to the rest of the ship. The first sign of the collection crew was a dead Cerean lying facedown with two holes in his head, wearing a standard Kelen Biolabs uniform. Kelen found a second corpse in a makeshift machine shop in the engineering area, someone who was once a scientist she knew. Upon entering the lounge in the living quarters, they witnessed the full extent of the carnage. Three bodies—a Sullustan male, a human female, and a Zabrak male—were scattered around the lounge, each bearing the marks of a skullborer attack. Skywalker opened a door that the Zabrak's body was blocking to head to the medical bay, and suddenly felt something landing on his helmet, which meant he was ambushed by skullborers.
Wielding a stun stick in each hand, Skywalker managed to knock one of the creatures off his body. However, while trying to get a look at the stunned creature, he lost his balance and fell to the floor due to his cumbersome armor. Two more skullborers landed on his visor, and the bottom one began to drill through his helmet while the other shielded it from the stun stick. Realizing that the stun sticks were ineffective, Skywalker reached for his blaster and fired without checking the setting. The laser blast killed the attacker, ending the skirmish. Although their mission was to investigate the moon and bring back any interests alive if possible, Nakari even killed the stunned ones in revenge for her dead friends.
As Kelen helped Skywalker up, another skullborer appeared and injured her left hand. After quickly shooting the attacker, they realized the skullborers were able to learn by their experience in the fact that the skullborer attacked the weapon hand, implying that they were at least semi-sentient. Skywalker treated Kelen with a bacta patch and allowed the automated medical system in the medical bay to continue. Skywalker resumed his investigation alone, wondering if the skullborers' intelligence increased based on what they ate, speculating that the Cerean's brain had improved their strategy. He eventually found the sixth and final crew member of the Harvester in the living quarters' third hatch on the left. The member was a human male, and although his look was most likely dead, his skull was still intact. As Skywalker leaned closer, he found out the man was still breathing. He threw the man over his left shoulder and hurried to the medical bay.
After taking him to Kelen, Skywalker cleared the ship, started the Harvester's engines, and ran preflight checks. He then dragged all the victims into the holding area and double-checked the ship with a life-form scanner he retrieved from the Desert Jewel. The scanner indicated that the ship was clear, and Skywalker linked the Harvester to the Jewel's navigation computer and successfully set a course for Pasher.
Upon arriving on Pasher, Nakari and Skywalker were met by Fayet Kelen and his employees. Nakari provided her father with a summary of the events, and Fayet asked Skywalker to erase all the data he had given to R2, as he wanted to protect his interests from others. Skywalker complied, but Nakari winked at him, indicating that she had made her own backup of the Fexian coordinates, which might be useful to the Rebel Alliance. Fayet thanked Skywalker for returning his ship and crew and cautioned Nakari to be careful before conducting further research on the moon. After spending a night at Pasher's finest hotel at Fayet's expense, Skywalker rejoined Nakari and planned their next move. Using the funds provided by Fayet, they decided to repaint the Desert Jewel to avoid Imperial detection and to equip the ship with weapons on Rodia.
The mission to Fex is featured in Heir to the Jedi, a canon adult novel authored by Kevin Hearne and released on March 3, 2015. It served as a primary plot point in the novel.