During the High Republic Era, Lily Tora-Asi, a Jedi Knight, mentored a human male Jedi Padawan named Keerin Fionn. Fionn, along with his Jedi Master, found themselves stationed at the Jedi temple located on Banchii.
Keerin Fionn, a member of the esteemed Jedi Order, was chosen to become the Padawan learner of Jedi Knight Lily Tora-Asi. Together, they were assigned to the newly established Jedi temple situated on the frontier world of Banchii. Under the guidance of Jedi Master Arkoff, the Jedi stationed on Banchii were entrusted with several crucial tasks: providing assistance to the newly formed settler village near the temple, venturing out to explore the planet's uncharted territories, and meticulously mapping its diverse terrain. Accompanied by Jedi Initiates Viv'nia and Nima, Fionn and his Jedi Master embarked on expeditions into the surrounding forests, seeking out unique native plant and animal species to be documented and preserved within the Temple Archives), which was maintained by Jedi archivist Ru-Ru. During one of these expeditions, the group of young Jedi made a significant discovery: Banchii was inhabited by small, bird-like beings residing in caves scattered throughout the region. When the Banchiians ensnared Nima in a simple trap, Fionn instinctively ignited his lightsaber. However, Tora-Asi seized the opportunity to impart a valuable lesson to her student, emphasizing the importance of patience and the need to wield the lightsaber with respect, avoiding reckless use.
As the Great Hyperspace Disaster unfolded and the Nihil emerged as a galactic menace, Fionn remained stationed on Banchii while his master undertook several supply missions between the Temple and the Jedi outpost located on Hon-Tallos. Upon his master's return, Fionn and the Initiates extended a warm welcome to her and the refugees she had rescued from the planet Ta'klah. Subsequently, they led the group of settlers on a guided tour of the Temple and the surrounding settlement. Later, as Tora-Asi and Fionn engaged in meditation near a serene pond, the Jedi Knight was suddenly overwhelmed by a troubling Force vision. Before they could decipher its meaning, they were joined by the Initiates and Master Arkoff, who encouraged the Master-Padawan duo to showcase their dueling prowess for Viv'nia and Nima.
While traversing the village and the adjacent fields, Fionn and his master received alarming news: Kooba, one of the settlers, had been mysteriously petrified within his own home. While Doctor Silar tended to Kooba's recovery, reports of ongoing disturbances within the village prompted Fionn and Tora-Asi to launch an investigation. As they explored the forest in search of clues, the Master and Padawan stumbled upon a trail of scattered debris leading towards the settlement. Rushing to the aid of the settlers, Fionn and Tora-Asi discovered several unconscious bodies strewn across the fields, accompanied by smoke billowing from the village center. The two Jedi identified the source of the chaos: a Drengir wreaking havoc throughout the village, devouring the inhabitants. Engaging the creature in combat, the Drengir ensnared Fionn with one of its appendages, but Tora-Asi swiftly intervened, using the Force to free him. They received assistance from Master Arkoff, who relentlessly slashed at the Drengir's flailing tendrils with his lightsaber, although they rapidly regenerated. Upon hearing a commotion emanating from the Temple, Tora-Asi and Fionn entrusted Arkoff with the task of confronting the initial attacker and sprinted to the aid of the settlers seeking refuge in the outpost. Arriving just in time, Fionn and his Master lured the second Drengir away from the Temple, but were perplexed by its ability to regenerate after each lightsaber strike. As Ru-Ru and Arkoff continued to engage the Drengir, Fionn assisted his Master in preparing several oil canisters near the lake in an attempt to defeat the Drengir. Guiding the creatures towards the lake and encircling them with oil, Fionn ignited the oil with a torch, engulfing the beasts in flames.
Following the Drengir attack, the Jedi of Banchii are convinced that the Nihil are planning an assault on their settlement, and they begin to fortify their defenses. With Master Arkoff absent, Fionn's master assumes leadership of the Temple, tasking the Padawan with overseeing the training of the Initiates. As Fionn drills them in lightsaber combat in the courtyard, he notices that the weight of leadership is taking a toll on his Master, and he offers to alleviate some of her burden after she lashes out at the playful children. When Sav Malagán, a Jedi Master from Takodana, arrives with a warning about the Nihil threat, Fionn listens intently as the two senior Jedi debate the optimal strategy for preparing for the impending assault. While Tora-Asi struggled with Master Malagán's disruptive personality, who advocated for arming the villagers and having them participate in their own defense during the impending attack, Fionn endeavored to support his master and the efforts of the settlers as they constructed bunkers for shelter. When an explosion at the worksite results in injuries, Fionn escorts the wounded to the Temple for medical attention, while Tora-Asi is compelled to confront the possibility that Malagán's perspective on her strategy is valid.
When Tora-Asi departed to consult with Starlight Beacon regarding future strategy, Fionn collaborated with Master Ru-Ru to identify the source of the issues plaguing their communications systems. Discovering that the central computer within the Temple had been sabotaged, Fionn hoped to alert Master Malagán, but the assault had already commenced. Igniting his lightsaber in defense of the settlers, Fionn directly engaged the Nihil, with the settlers providing covering fire from the Temple gates. As Fionn fought valiantly, his master returned to Banchii and joined the fray. Amidst the chaos, Initiates Viv'nia and Nima vanished, prompting Fionn to rush off in search of them, ensuring their safety from the Nihil marauders. Locating the Initiates conferring with Banchiians in the forest, Fionn was accompanied by Master Malagán, who stood ready to provide assistance if needed. The natives led the four Jedi to a clearing in the forest, where a group of Nihil were gathered around a cannon they had positioned to attack the Temple. After the Initiates had been sent to safety, Fionn disregarded Malagán's caution and charged into the clearing when the Nihil turned their backs. Holding his blade to the throat of one of the marauders and demanding that the others surrender, Fionn was caught off guard when the Nihil revealed a prisoner: Mr. Zaret from the village. Deactivating his lightsaber and releasing the captive Nihil in exchange for Zaret's life, Fionn was left vulnerable when Zaret drew a blaster and fired a fatal shot, striking Fionn's heart and ending his life instantly.
Unable to react swiftly enough, Malagán emerged from her hiding spot and swiftly dispatched the Nihil. Joined by Tora-Asi, who had sensed Fionn's passing through the Force, Malagán urged the young Knight to persevere and not allow grief to paralyze her. As the Nihil launched their assault on the Temple itself, the Jedi returned, resolved to fight on in Fionn's memory. Recognizing the unfavorable odds, Tora-Asi ordered the evacuation of the Temple before launching missiles into its structure to prevent the Nihil from seizing its treasures. With the battle concluded, the Jedi returned to the clearing to retrieve Fionn's body. As the other Jedi departed for Coruscant, Tora-Asi remained with Fionn's body, taking possession of his lightsaber and vowing to remain as the protector of Banchii and its native inhabitants, honoring the life of her student.
Keerin Fionn made his debut in the first volume of the 2021 Japanese manga series Star Wars: The High Republic: The Edge of Balance, authored by Justina Ireland and Shima Shinya, and brought to life through the illustrations of Mizuki Sakakibara. In The Art of Star Wars: The High Republic: Volume I, his concept art is identified as "Rowan."