A Force-sensitive Human, Rori Fenn and her brother Jake Fenn were trained in the ways of the Force by the Je'daii Order on the planet Tython, one of nine planets in the Tython system which made up the Settled Worlds. As a Journeyer, Fenn had a romantic relationship with fellow Journeyer Hawk Ryo; the pair ended the relationship after they ascended to the rank of Je'daii Ranger. An adherent of the Balance philosophy which guided the Je'daii, Fenn had struggled to remain in Balance, falling to the light side of the Force during her career. Noting this, the Je'daii Council exiled Fenn to the moon of Ashla, where she was tasked with meditating on the dark side and returning to the Balanced center necessary of a true Je'daii. After some time, Fenn was permitted to leave Ashla and return to active duty with the Order. During her life as a Ranger, Fenn carried a single Force-imbued blade and wore blue armor as a defense against the wilds of Tython.
In 25,793 BBY, the Xesh, a Force Hound of the Infinite Empire crashed the Rakatan ship called the Devourer near the Rift on Tython. The surge of deaths associated with the crash alerted all Je'daii to the foreign presence on the world, as well as stirring a Force storm that would rage across the entire planet. Fenn was at the Temple of Balance, Akar Kesh, where she consulted with Temple Master Ketu regarding the anomalies spreading across the world. Dispatched by Master Ketu to the crash site in Hunter-class starfighters, Fenn accompanied fellow Ranger Hawk Ryo and Temple Master Quan-Jang to the Rift in search of survivors. Despite being attacked briefly by a pair of saarl, the Je'daii arrived safely at the site where they were able to transmit a vid-feed back to Temple Master Kora Ryo at the Temple of Knowledge, Kaleth.
Discovering the broken hilts of three Je'daii Journeyers' swords, Fenn and Ryo paired up on the back of a bipedal mount and delved deep into the Rift in search of their wayward Je'daii while Master Quan-Jang surveyed the area on the back of a mutated rancor-dragon named Butch. As the storm intensified, the three Je'daii were forced to enter the perilous Abyss of Ruh together on foot, hoping to find the wayward Je'daii Journeyers before it was too late. Tracking the quarry for hours, the trio eventually found Journeyers Shae Koda, Tasha Ryo, and Sek'nos Rath engaged in battle with a saarl, and the Force Hound Xesh at the nexus of the Force Storm. Fenn and Ryo joined the battle to allow Quan-Jang the opportunity to release the tension in the Force above. Fenn confronted Xesh directly after the saarl was destroyed, ordering him to surrender so that they might help him find Balance and end the conflict. While Xesh refused to be taken prisoner, he was overpowered by a surge of light side energy directed at him by Quan-Jang, allowing for the Je'daii to arrest the stranger and dissipate the Storm. Taking the Force Hound to Mahara Kesh for treatment of his injuries, Fenn joined Ryo in escorting Xesh from Tython to the moon of Bogan where he was to be imprisoned in forced meditative reflection on the light side of the Force.
Months after Xesh's arrival in the Tython system, the Je'daii were struggling to understand the fallout of the mysterious being's nature. Fenn joined Master Tem Madog at Vur Tepe, where the Forge Master tried to uncover the secrets of the Forcesaber. When Hawk Ryo managed to ignite the blade by drawing only on the dark side of the Force, Fenn warned against walking too long in the dark due to its corrosive nature. While Ryo heard her out, he rejected the paralyzing effects of relying too much on the light side and continued his studies with the weapon. Not long after, the Je'daii received word that Xesh was missing from his cell on Bogan and Fenn joined Ryo and Shae Koda in investigating the disturbance on the moon. While her brother Jake Fenn, Sek'nos Rath, and the tracker Bel Zana looked into Xesh's cell, Fenn, Ryo, and Koda discovered the remains of a downed Pho-V fighter in Daegen Lok hidden cave. As Ryo recalled the vision of a dark army he shared with Lok years early, the Twi'lek Ranger came out of balance and grabbed Fenn by the throat in a fit of rage.
Recovering from the attack after Koda helped Ryo to center himself, Fenn pushed Ryo for information on this vision for years past. Ryo believed that Lok's obsession with a sword of fire would lead him to join forces with Xesh to create a new Forcesaber. Deducing that the pair of fugitives would seek material on Krev Coeur and Nox, the trio headed for the later, while the other Je'daii team headed to the crystal world of Krev Coeur. On Nox, the trio infiltrated Boneyard City, battling a mutant slashrat as they entered the ruins. Tracking Xesh and Look to , Fenn chased Lok through the city as he fled an ambush by Ranger Ryo. Though she lost track of Lok, Ryo confronted an illusion of the exiled Je'daii and deduced he was making for the spaceport. Having lost contact with Shae Koda, Ryo and Fenn figured that their quarry had abducted her and had sought safe harbor on Shikaakwa.
Rendezvousing with Sek'nos Rath and his new ally Trill in the sewers beneath Ryo Fortress on Shikaakwa, Fenn and Ryo entered into mighty palace and confronted crime lord Volnos Ryo who had received Xesh and Lok. As Lok collapsed the ceiling to mask his escape, Fenn and Rath gave chase to a fleeing Xesh and his prisoner, Shae Koda. Fenn came upon Lok on the rooftop of the Fortress, and was soundly defeated when Lok's Forcesaber cut through her sword.
When the Infinite Empire invaded the Tython system, Fenn joined the Je'daii armies, flying alongside Hawk Ryo in defense of the Settled Worlds. After the Battle of Shikaakwa saw a Je'daii victory, Fenn gathered with the other Je'daii as General Daegen Lok called for celebration. After the gathering dispersed, Fenn remarked to Ryo that Lok's love of war was unbecoming of a Je'daii.
During the Second battle of Tython, Fenn and Ryo flew together, battling the Rakata fleet above Anil Kesh. At the height of the pitched battle, Fenn and Ryo were flying around the Tho Yor which hovered over Anil Kesh Temple as it began to glow and fire rays of golden light at the Rakata fleet.