Valin Horn, a male Human Jedi Knight, was born to Corran Horn and Mirax Terrik Horn. He also had a younger sister, Jysella Horn. The year 43 ABY saw him become one of the initial Jedi afflicted by Force psychosis, which led to his imprisonment in carbonite.
This member of the Horn family, Valin, was named in honor of his paternal grandfather, Valin Halcyon. His birth occurred roughly four years following Grand Admiral Thrawn's campaign against the New Republic. Possessing a talent for music, he frequently played his chordokeylo. Being Force-sensitive, he eventually began training as a Jedi Knight at Luke Skywalker's Jedi Praxeum located on Yavin 4.
Horn cultivated abilities akin to those of Jacen Solo, notably his affinity with animals. Around the age of eleven, he discovered his capacity to communicate with animals via the Force. However, similar to his father and grandfather, he exhibited weakness in the skill of telekinesis. In one instance, unable to levitate a stone using telekinesis, Valin instead employed the Force to induce small insects known as garnants to relocate the stone by convincing them it was a food source. His father, witnessing the stone's movement, initially believed Valin had used telekinesis until his son clarified his method. He then provided food for the garnants, fulfilling his promise before departing.
During the Yuuzhan Vong War, Horn and his fellow Praxeum students were stranded on Yavin 4 when the Peace Brigade established a blockade of the system. Fortunately, Horn, along with Sannah and Kam Solusar, managed to endure until they could escape during Anakin Solo's perilous endeavor to rescue the trapped Jedi. Subsequently, Horn dedicated time to training with the remaining Jedi initiates aboard the Errant Venture, the ship of his maternal grandfather, Booster Terrik.
Following the Battle of Coruscant, he and the other young Jedi were relocated to the Maw for their safety for the war's duration. As the conflict concluded, Horn journeyed to Zonama Sekot for a meeting between Grand Master Skywalker and the surviving Jedi.
By the time the Second Galactic Civil War erupted, Horn was undertaking missions for the Jedi Order. Given his age, it's reasonable to assume he had attained the rank of Jedi Knight. As tensions rose with his ancestral homeworld, Corellia, Grand Master Luke Skywalker strategically assigned him duties far from any potential conflict of loyalties.
During a mission in the lower levels of Coruscant, accompanied by Jedi Master Kyle Katarn, fellow Jedi Knights Thann Mithric and Kolir Hu'lya, and Jedi apprentice Seha Dorvald, Horn and the group encountered Jacen Solo. The resulting confrontation led to Katarn suffering a severe chest wound from Solo's attack, compelling Horn and Dorvald to extract him from the battle, which ultimately resulted in Mithric's demise.
Horn later participated in the operation to destroy Centerpoint Station, disguising himself as a Galactic Alliance Guard trooper alongside fellow Jedi, including Kyp Durron and Jaden Korr.
In 43.5 ABY, Valin Horn was unexpectedly struck by a mysterious madness that warped his perception, leading him to believe that everyone he knew had been replaced by impostors. Driven by this delusion, he turned against his own parents, only to be subdued and brought to the Jedi Temple for evaluation. However, he escaped and became a fugitive pursued by the Galactic Alliance, further fueling Chief of State Natasi Daala's distrust of the Jedi. After an extensive search, Luke Skywalker apprehended him and confined him to the Mon Mothma Memorial Medical Center, later transferring him back to the Asylum Block.
Subsequently, Daala issued a warrant for Horn's arrest, leading to his capture by Galactic Alliance Security forces under Captain Oric Harfard. He was then subjected to trial. Deemed unfit to stand trial but too dangerous for conventional imprisonment, he was encased in carbonite and incarcerated in the Armand Isard Correctional Facility. A rescue attempt to liberate Horn was launched by the rogue Jedi Seff Hellin, who was also afflicted with the same ailment and believed Horn to be the only genuine individual remaining. However, the attempt failed, resulting in Hellin's capture by Darkmeld, a clandestine organization established by Jedi Knight Jaina Solo to counteract Daala's efforts to undermine the Jedi Order.
Sometime after the failed rescue, Valin, along with his sister, was moved to the Palem Graser Office Tower, a concealed GAS safehouse overseen by Colonel Wruq Retk and operating under the guise of Galactic Alliance Storage. The Jedi Order secured a writ granting them visitation rights to the siblings, along with an incarceration order revealing their location. Following a brief attempt to deny the visitation group, which included Corran and Mirax Horn, the GAS officers directed the Jedi to the siblings' location. The Jedi, along with numerous HoloNet Reporters who had arrived, were horrified to discover that Valin and Jysella were being displayed as decorations in the executive offices. When Colonel Retk entered the room, he engaged in a short conversation with Mirax Horn before she incapacitated the Yaka with a blow. The incident caused embarrassment for the GA Government, with Daala promising to ensure the carbonite-frozen siblings would be treated with respect. After being freed from his carbonite prison, Valin and his sister were still inflicted with the Force psychosis. He was able to conceal his condition, being more in control of his emotions and suspicions than he was previously.
During his youth, Valin Horn was a follower with aspirations of becoming a hero. He aspired to possess the same Jedi prowess as Anakin Solo, which led him and several other young Jedi into various predicaments when Solo arrived on Yavin 4 to rescue Tahiri Veila.
Mirroring his father, he lacked strength in telekinesis but compensated through his affinity with animals. On one occasion, his father, Corran Horn, expressed pride upon witnessing Valin seemingly "lift" a rock a minuscule distance from the ground. In reality, Valin had manipulated a nest of garnants into perceiving the rock as food. Shortly after, Ganner Rhysode arrived and implied that Valin would only ever be a failure, prompting Valin to manipulate the garnants into perceiving Rhysode as food. In a way, Valin had made Rhysode eat his words. He once again manipulated insect life when he was being held for observation in the Jedi Temple after he exhibited traits of a mysterious illness. He successfully called the bugs to him through the Force and had them chew through the restraints on his medical bed in order to escape.
As an adult, Valin was described by his sister Jysella as level-headed and easygoing, as well as gentle. The Solos noted that both Valin and Jysella were well-regarded within the Jedi community.