Orphaned at a young age due to a train wreck that took both his parents and his grandparents, Zell was adopted at the age of 8 into Template's military academy, known as Garden. Founded by the city's Chief of Police and run by headmaster Cid Kramer, Garden was well known for taking in fosterlings and training them to be skilled and effective soldiers and law enforcers. The most talented were selected to undergo special training and testing to become SeeDs, Garden's elite military force that specialized in dealing with sorceresses: unique women with a special connection to the spiritual level that allowed them to affect reality. SeeDs in turn were gifted with the control of Guardian Forces, mysterious entities existing on the spiritual level of the city that could affect both the digital and physical levels below.
As a child, Zell was known as the class clown, possessed of a quick temper and prone to acting out. He got into fights frequently, and his performance in school was substandard due to his lack of motivation and inability to follow orders. This continued all the way into his teenage years, and prevented him from having any close friends. Lonely and craving attention, his behaviour took a turn for the worse until Garden issued an ultimatum: clean up his act, or be expelled.
Faced with the very real possibility of losing the only home he'd ever known, Zell did a total turnaround. He began following orders diligently, concentrating on refining his skills and improving himself as a fighter. He found a new joy in practicing martial arts, and spent much of his free time creating combos and new moves. He began earning above-average marks, securing him a spot as a SeeD candidate.
Despite this drastic improvement, Zell still had difficulty controlling his emotions and his temper, and his social life continued to suffer for it. Even though he now possessed more self-control and discipline than he had before, his reputation as a brawler had already been established, and it preceded him wherever he went in the school. He nevertheless continued to put on a friendly face, often making an extra effort to be as sociable as possible. He began to look up more and more to his instructors, and had a tendency to idolize those he admired.
Then, when Zell was 18, the sorceress Edea led the Galbadian army against Template in an offensive invasion. Garden was mobilized to drive the sorceress back, and Zell passed his SeeD test by participating in the counterstrike. He was promptly assigned to the group charged with pursuing Edea and assassinating her, which, at the time, was considered to be a standard enough SeeD mission. Zell's team (led by Squall) warped to Edea's position using the digital level, only to discover that a fellow Garden student, Seifer, had defected to the sorceress's side during the earlier attack, and that Edea's power was far beyond what any of them had expected. Seifer and Edea defeated the team and made their escape, leaving the SeeDs to regroup at Garden.
Upon hearing their report, Garden determined that, having already engaged the sorceress once, Squall's team was ideal for gathering further information on her so that a plan of action could be decided upon. The team was split into two groups - Selphie, Irvine, Quistis, and Zell, Squall, Rinoa - with orders to infiltrate Galbadia and ferret out Edea's hiding place, as well as any other relevant intelligence they could gather. By this point, however, Edea had disrupted the digital level over Galbadia, making it impossible to warp in, and forcing both teams to infiltrate on foot in hostile terrain.
Almost inevitably, Zell's team was discovered and brought to be imprisoned at a security facility in the city of Dollet, where they were separated and tortured interrogated for information, both by Galbadian soldiers and by Seifer himself. Eventually both Zell and Squall managed to overpower the guards and escape their cells, freeing Rinoa from the special solitary confinement she'd been placed in. She explained to the boys that while they were interrogating her, the Galbadians had discovered that Rinoa had latent sorceress abilities, and planned to keep her there for experimentation of the not-very-nice type. Unable to gather any information without risking being recaptured, the trio escaped the facility.
Quistis' team had narrowly evaded capture themselves, and were waiting at the prearranged meeting spot inside Galbadian borders. Seifer had let slip Edea's location to Squall while in the prison, and the group made the hard decision to continue on with their mission rather than going back to Garden. After a long and very difficult journey, they found and engaged Edea and Seifer in their second battle, where they again found themselves outmatched against Edea's power. But just as Edea was preparing to eradicate the team with her sorceress abilities, Rinoa's latent powers awakened and apparently drove the sorceress back, causing her to collapse unconscious.
But before the team could approach Edea to confirm her status, Rinoa suddenly turned on her fellow SeeDs and attacked them, using abilities that mirrored Edea's but were even greater in power. She spoke in a voice not her own, and didn't respond to any of her teammates' pleas for her to stop, eventually forcing the others to beat a narrow retreat or be killed. They backtracked across Galbadia to Template and Garden, where they discovered that in the time it had taken them to return, Rinoa had taken up Edea's place -- and that new plans were made for the retrieval of Edea and the assassination of Rinoa, despite the protests made by Squall and the others.
When it was clear that Garden would not back down on the assassination mission, Squall defied orders in order to go retrieve her himself. Zell and the others went with him, along with Ellone, Squall's sister -- raised in a regular nearby orphanage and therefore not a SeeD, she nevertheless had a strong connection to the spiritual level that she believed would be of some help. Re-entering Galbadia along a different route, they managed to find and confront Rinoa, but not before running into Seifer -- resulting in a definitive one-on-one duel between him and Squall. Squall emerged as the victor, but badly injured. The rest of the team was forced to attack Rinoa, only to be handily defeated yet again. In the final moments of the battle, with all of them facing what looked like certain death, Squall managed to pick himself up and engaged Rinoa himself in a desperate last-ditch effort to wake her up. Something in Rinoa hesitated just long enough for Ellone to contact her spiritual self and aid her in throwing off whatever was controlling her mind. Rinoa came back to herself, weakened and disoriented, and the team limped back to Garden with Edea and Seifer in tow.
At Garden, it was discovered that Rinoa had been possessed by another, more powerful sorceress by the name of Ultimecia--who had, not coincidentally, also possessed Edea, as well as a sorceress by the name of Adel who had attacked the city some years ago. Due to Ultimecia having been in her mind, Rinoa had obtained knowledge of the older sorceress' goals: she planned to compress the entire spiritual level into a single, controllable entity, in order to be able to shape the reality of the world to her whim. But since the spiritual level would often strike back against those who tried to manipulate it directly, she possessed other sorceresses so that they would suffer the backlash in her place. Edea and Rinoa had been freed before Ultimecia had used their powers enough to cause that backlash, but Adel and other sorceresses in other countries had already died or lost their powers as a result of it. As Ultimecia gained the powers of the spiritual level in a given area, she would use her influence to turn the people of that country in her favour, as she had in Galbadia -- supplying her with armies to invade other countries and subdue more sorceresses for her use.
Armed with this information, all of Template's military forces were turned to the task of stopping Ultimecia -- with the exception of Squall's group, who was confined to Garden by the Chief of Police himself under the reasoning that they were a threat to the mission, due to their earlier actions and failure to follow orders. Despite her protests that she was the only one who could stop Ultimecia, Rinoa was separated from them and put under observation, in case Ultimecia attempted to possess her again. They remained under arrest for several days while Template marched against Galbadia -- and Ultimecia, who was waiting and ready for them. Her Galbadian soldiers had the added advantage of being able to use the digital level both inside and outside of Galbadia, whereas Template soldiers couldn't warp beyond the border and had to continue on by foot. Hundreds died, cut down by Galbadians who would warp straight into the midst of troops and begin attacking, cut down by lethal sorcerous spells -- and still Template got no closer to reaching Ultimecia. Her powers had grown to the point where she could detect any non-Galbadians as soon as they crossed the border, and her army allowed no one to get any further than that.
Squall's group had begun to despair when they were suddenly and inexplicably released from their confinement, with orders that they were to infiltrate Galbadia yet again and this time destroy Ultimecia with Rinoa's aid. It turned out that Cid Kramer had confronted the Chief of Police and convinced him to let the SeeDs go, on the condition that if they returned without killing the sorceress, they would be placed back in confinement and court-martialed. Faced with little other option, they went, infiltrating Galbadia for the third time under cover, with Rinoa using her powers to keep Ultimecia from detecting their presence.
They had made it almost into the center of the state before they discovered that Ultimecia wasn't in Galbadia at all--she had taken refuge in the country of Esthar, further to the north. The team split up yet again, with Zell, Selphie, and Quistis heading back to Garden to inform them of the change in the situation, while Squall, Rinoa, and Irvine continued on towards Esthar so as not to violate their mission conditions. At Garden, Zell's group was granted use of the Ragnarok fighter airship in order to collect the rest of their team and continue on to Esthar. While they were there, Edea and Seifer insisted on accompanying the team, citing that they too had knowledge that could be vital in defeating Ultimecia. After some deliberation, Garden allowed Edea to go -- but only on the condition that she be implanted with a special explosive device that could be used to remotely destroy her should she be possessed by Ultimecia again. Seifer's demands were denied, on the grounds that he was too unpredictable to have on such a vital mission.
With Edea on their team and Selphie piloting, they collected Squall and the others and entered Esthar. Squall was entrusted with the trigger to Edea's device, something that didn't sit well with him. The situation was further aggravated when they discovered that Seifer had stowed away on the ship before it left Template, intent on participating in this final battle. After much arguing, Squall allowed him to stay, and all eight ventured on foot towards Ultimecia's stronghold, in order to keep from attracting her attention.
The stronghold was a twisting and dangerous structure that existed on the physical, digital, and spiritual levels all at once. Seifer and Edea had enough knowledge of the place to lead the others through it, but it was still a grueling and disorienting experience, testing the limits of the SeeDs' minds and physical endurance. Ultimecia detected their presence before they were able to reach her, and incapacitated Edea and Seifer, forcing the others to continue on without them. The final battle with Ultimecia was long, desperate, and nightmarish, with terrifying monsters and the very surroundings of the stronghold changing and attacking to her advantage. In the end, Edea sacrificed her sorceress powers to Rinoa, allowing the girl to overpower Ultimecia and leave her vulnerable to a concerted attack from all the SeeDs. Ultimecia was destroyed, and without her power to sustain it, the stronghold began to collapse.
Rinoa was able to use her new powers to keep the structure standing long enough for them to retrieve Seifer and Edea and escape, although the effort left her half-aware and unable to walk. The boys had to take turns carrying her, and everyone made it out only moments before she lost her control and the stronghold fell to pieces. Injured and bone-weary, the group flew the Ragnarok back to Garden, where they were hailed as heroes and granted a well-earned rest while Template dealt with restoring order to the countries Ultimecia had been controlling.
Seifer was finally granted SeeD rank, and the others were elevated to SeeD's elite ranking, specializing in handling sorceress uprisings. Rinoa, with the support of Squall and the others and worried about how Garden might abuse her power, left SeeD and instead established a contract with Garden as an independant mercenary, allowing her to continue working with them under her own conditions.
As they continued living at Garden, the group slowly began drifting apart again, each concerned with their individual missions and personal problems. Zell considers his Template!canonmates good teammates and works well with them, but he doesn't share the same deep friendship with them that he does in the game, furthering his social isolation.