The Elphrona Expedition occurred in 19 ABY during the New Republic Era. Jedi Master Luke Skywalker, accompanied by his Padawan and nephew, Ben Solo, and the explorer Lor San Tekka, journeyed to the planet Elphrona. Their objective was to locate Jedi artifacts within the planet's Jedi outpost.
En route to Elphrona, the shadowy figure of Snoke seized the opportunity to plant seeds of doubt in Solo's mind concerning the Jedi Order. Simultaneously, inside the outpost, the Jedi and Tekka encountered the Knights of Ren, a group of masked dark sider warriors.
During the High Republic Era, a period marked by increased Jedi involvement across the galaxy, the Jedi Order visited Elphrona. They then constructed an outpost built into the side of a cliff. This outpost served as a repository where the Jedi stored a variety of artifacts.
Back in 3 ABY, the young Jedi Padawan Luke Skywalker journeyed to Tempes, entering the planet's Jedi outpost that was originally built during the High Republic Era. His goal was to find a replacement lightsaber after losing his previous one during his duel with Darth Vader. Although Skywalker successfully acquired a new lightsaber, he also inadvertently triggered a trap, releasing the spirit of the Grand Inquisitor, whom he ultimately defeated in a fierce battle.
During the New Republic Era, Skywalker had advanced to the rank of Jedi Master and was in the process of rebuilding the Jedi Order. Recognizing his need for deeper knowledge of Jedi history to effectively restore the Jedi and prevent the resurgence of the dark side, Skywalker began a galaxy-wide search for any surviving Jedi texts and artifacts.
In 19 ABY, Skywalker learned about Elphrona and its Jedi outpost from his explorer and trusted friend Lor San Tekka. Tekka had discovered the outpost through one of his contacts. Despite initial skepticism, the Jedi Master decided to travel to Elphrona with Tekka and his Padawan Ben Solo.
While traveling aboard a starship, Skywalker and Tekka discussed the High Republic Era, highlighting it as a time when the Jedi expanded their presence significantly beyond the Core Worlds. Solo expressed his discontent with the extended journey to the edge of known space. From a distance, the enigmatic Snoke saw this as an opportunity to instill doubts in Solo's mind about the Jedi, suggesting that they had a history of hoarding knowledge and power, viewing themselves as masters of the Force and that Skywalker was impeding his growth as a Jedi. Snoke assured him that Skywalker would eventually recognize Solo's true potential, but currently saw him as a mere child.
Upon arriving on Elphrona, the trio discovered that the entrance to the outpost had remained intact over the years. Tekka was excited by the outpost's well-preserved state, but Skywalker cautioned Solo to be careful, recalling his experience on Tempes where he triggered a trap more than a decade prior. Solo assured him he would be cautious. Inside the outpost, Skywalker observed that many artifacts were still intact, which amazed Tekka and Solo. The Jedi Master discovered a Jedi holocron, while his padawan found a lightsaber rifle.
Both Skywalker and Solo sensed a presence through the Force, realizing they were not alone in the outpost. The Knights of Ren soon appeared before them. Ren declared that the artifacts belonged to the Knights, issuing a threat to Skywalker. However, the Jedi Master intended to prevent the Knights of Ren from claiming the artifacts. Ren then ignited his lightsaber, and the Knights charged at Skywalker, who instructed Solo to protect San Tekka. Despite being outnumbered, Skywalker skillfully fought the knights, effortlessly dodging their attacks and deflecting their blasts. While Skywalker acknowledged that he was just one person, the Jedi knew he was not alone, with the Force as his ally.
Tekka and Solo watched in awe as Skywalker quickly subdued the Knights, criticizing their clumsy use of the dark side before destroying their weapons. With the Knights defeated, Ren stepped forward to confront the Jedi himself. The leader of the knights revealed that he had activated a kill switch on his lightsaber, which would cause it to explode if it left his hand. Before departing, Ren told the Jedi Master that he could sense the dark side within Solo, before unmasking himself and inviting the young padawan to contact the Knights if he ever desired to explore the dark side further.
Ren discarded his helmet on the ground after extending his invitation to Solo before leaving. Following his encounter with the knights, one of Luke's students, Voe, learned about the confrontation on Elphrona.
Solo would eventually accept Ren's offer and seek out the knights during his descent into the dark side following his destruction of the Jedi Temple years later, joining the knights as an initiate shortly after a brief confrontation with his fellow Jedi on Elphrona, which culminated in Solo destroying the outpost.
Solo would return to Elphrona one final time during the First Order-Resistance War, now identifying as Kylo Ren and leading the Knights of Ren after killing their previous leader. This return was part of his plan to force his former Jedi Master to reveal himself, as he still sensed Skywalker's presence after his death.