Jann Tosh, a youthful miner, resided on the obscure world known as Tyne's Horky. Around the age of twenty years, his life took an unexpected turn when he encountered the droids, specifically C-3PO and R2-D2.
Born on Naboo, Jann Tosh was the offspring of Gar and Plena Tosh. His parents later expanded their family with twins, named Gessle and Trif. Tragically, all four perished in a speeder accident around 19 BBY, leaving Jann an orphan.
Bereft of any immediate family, Jann Tosh came under the care of Putch Gundarian, his father's closest confidant, on the remote Mid Rim mining planet of Tyne's Horky. Putch requested that Jann refer to him as "Uncle Gundy." Enduring the demanding life of a miner in pursuit of Keschels, while simultaneously harboring aspirations of becoming a pilot, Jann's circumstances dramatically shifted when he stumbled upon a frightened protocol droid and its astromech companion at a local droid marketplace.
After procuring a much-needed Mining droid to assist at his uncle's mining site, Jann felt sympathy for the protocol droid and R2 unit. He had observed the harsh treatment that their new owner Yorpo Mog inflicted on a gangly Android. Consequently, Jann traded his mining droid to Mog to obtain R2-D2, C-3PO, and the barely functional android. Jann then loaded the droids onto his 48 Roller wheel bike and prepared to head home. However, before he could even start the wheel bike, he spotted an enraged Yorpo Mog rushing towards him. Jann quickly started the bike and sped away, but not before Yorpo jumped aboard. After a wild ride through the desert, Jann managed to eject Mog from the vehicle and reach the safety of his home.
Following his uncle's initial anger over the new droids, Jann soon realized that the android was not a droid at all. It was actually a frail and delirious alien. Eventually, the alien, named Kez-Iban by Jann (which translates to 'Bocce for 'he who returns from death''), became a valuable asset at the mine. On one occasion, he even rescued Gundy from a mine collapse.

As Jann, Kez-Iban, and the droids were transporting Gundy to the nearest medical facility for treatment, they were noticed by Yorpo Mog and his employer Kleb Zellock. Zellock had been tasked with locating the missing prince of Tammuz-an, Mon Julpa. Convinced that Jann's purple-skinned companion was the person he sought, he dispatched Yorpo to capture him. After being alerted by R2-D2 about the abduction, Jann immediately went to Doodnik's Café, Kleb's preferred hangout, to confront the kidnappers. Upon arrival, Jann discovered Kleb and Yorpo mistreating the Tammuz-an Sollag Den, a friend of Mon Julpa who had hired Kleb to find the prince. A fight broke out, and Jann narrowly avoided injury thanks to the intervention of a female freighter captain named Jessica Meade. However, as Jann and the droids left Doodnik's, they were immediately seized by Yorpo Mog and two of his droids and taken as prisoners to Kleb Zellock's Nergon-14 mine.
Imprisoned deep within the mine, Jann was reunited with Kez-Iban, who was also being held captive. Thanks to the ingenuity of Jann's droids, they quickly broke free from their restraints and defeated one of the mining droid guards who had just thrown Sollag into their cell. After returning Kez-Iban's royal scepter, which had been hidden under Sollag's robes, the Tammuz-an prince regained his memory and was now able to communicate.
Jann and his companions began their escape, battling the armed mining droids that stood in their way, eventually reaching the office of Kleb and his henchman Yorpo. Kleb incapacitated Jann, Mon Julpa, and Sollag with a piercing siren, then fled the room as the Nergon-14 deposits in the mine began to erupt. Just as he was about to escape on the only available skiff with a stash of Keschels, Kleb betrayed his accomplice Yorpo, leaving him to die in the explosion. However, thanks to an intervention by C-3PO, who had just arrived on the scene, Yorpo was able to stun Kleb. Moments later, Jann and the rest of his companions arrived, boarded Kleb Zellock's custom skiff along with Yorpo and the unconscious gangster, and fled the mine just before the Nergon-14 erupted in a massive explosion.
Upon returning to his uncle's claim, Jann learned that Gundy had discovered a Keschel vein in his mine as a result of the cave-in. With his uncle now wealthy, Jann decided to leave Tyne's Horky and accompany Mon Julpa and Sollag back to Tammuz-an to assist the Prince in reclaiming his throne.
During the journey to Tammuz-an aboard the freighter, Jann discovered that their pilot was none other than Jessica Meade, the woman who had saved him at Doodnik's Café. Shortly after their meeting, the ship was attacked by the pirate crew of Captain Gir Kybo Ren-Cha. Jessica's freighter was destroyed in the assault, except for a small section including the cockpit, which detached from the main craft and flew independently. As the pirates closed in for the kill, Jann and his friends were unexpectedly rescued when the bounty hunter IG-88, hired to collect a bounty on Mon Jupla, attacked the pirates from his starfighter.
Following their nighttime arrival on Tammuz-an, Jann assisted Mon Julpa and Sollag in devising a plan to avoid capture by the power-hungry vizier Ko Zatec-Cha. Their goal was to reach the Keeper of the Tower and present the Tammuz-an Royal Scepter before the first sunrise of the equinox, enabling Julpa to assume the role of King. However, before they could execute their plan, Julpa was captured by IG-88, and the Royal Scepter was handed over to Zatec-Cha. Jann and his droids were left with no choice but to quickly organize a rescue mission to free the Prince and Jessica, who had also been captured, and retrieve the Scepter from Zatec-Cha before the vizier could use it for his own coronation. With the help of his droids, Jann's mission was successful. He rescued Mon Julpa from being fed to a Durkii, saved Jessica from her captors, and helped Julpa regain the Scepter during an aerial battle fought with small one-man Repulsorcrafts. Immediately after his coronation, Mon Julpa appointed Jann a captain in the space navy of Tammuz-an.

During one of his initial assignments for King Julpa, Jann was piloting an escort mission in an R-22 Spearhead for a supply ship carrying fuel when Kybo Ren-Cha's pirates attacked. When the pirates seized the supply ship and its captain, Jessica Meade, Jann was compelled to surrender to prevent harm from coming to Jessica, R2-D2, and C-3PO. With his fighter ensnared in the pirate's tractor beam, Jann and the fuel tanker were transported to Kybo Ren-Cha's headquarters on the planet Tarnoonga. While imprisoned by the pirates, Jann learned of the pirate captain's scheme to conquer Tammuz-an. Without the fuel from the supply ship, Tammuz-an's space navy would be unable to defend against Kybo's captured Imperial Star Destroyer, the Demolisher.
Jann and his companions were then transported via a Bantha-II cargo skiff to a sea region known to be inhabited by a Miridon. After being thrown into the water, Jann was rescued from the creature by R2-D2, who had jumped into the ocean with C-3PO, and taken to the safety of a cavern beneath the pirates' headquarters. After infiltrating the pirate hideout, Jann and the droids reunited with Jessica, located their spacecraft, and escaped.

Before Jann could return to Tammuz-an, he and the droids were captured by the Demolisher's tractor beam. While Jann was imprisoned on the pirate Star Destroyer, Kybo destroyed the fuel tanker shortly after Jessica ejected in an escape pod. Upon realizing that the ruptured tanker contained no fuel, Jann revealed that his escort mission was a decoy and that the real supply ship had safely reached Tammuz-an. At that moment, Mon Julpa's fighters launched an attack on the Demolisher as R2-D2 sabotaged the vessel by causing its torpedoes to backfire. Racing to the Star Destroyer's hangar, Jann and his droids managed to reach the captured R-22 Spearhead and escape the pirates.
Following the capture of the pirates, Jann became an advisor to Mon Julpa during peace negotiations with the warrior chieftain Lord Toda. However, the negotiations were complicated when Kybo escaped from Julpa's dungeon and fled aboard an R-22 Spearhead with Toda's daughter Gerin as a hostage. Jann and Jessica were tasked with rescuing Gerin, while Julpa placed himself in Toda's custody as a gesture of goodwill. After C-3PO and R2-D2 learned of Kybo Ren's destination from the imprisoned pirate Jyn Obah, Jann, Jessica, and the droids set off for the bog moon of Bogden. Their rescue mission was successful, and Lord Toda's forces finally defeated the pirates. Following the mission, Jann bid farewell to Jessica as she departed for Tyne's Horky.

After Jessica Meade's return to Tyne's Horky, Jann decided to pursue his ambition of joining the Imperial Space Academy. While awaiting his acceptance notification, he continued to serve Mon Julpa and Lord Toda, volunteering to escort Toda's headstrong son Coby to the Imperial Academy's retraining program. However, during a stopover at the Zallakesh spaceport on the world of Chuzalla, Coby became separated from Jann after the young Prince purchased a starfighter and set off with Jann's droids in pursuit of the Starhunter's Intergalactic Menagerie and Coby's stolen pet. Receiving an SOS from Coby, Jann was able to catch up with the boy on the planet Dandelo and end the Starhunters' illegal operation. It was there that Jann revealed to the droids that he had finally been accepted into the Academy. Unfortunately, trainees were not allowed to bring their droids, so Jann reluctantly parted ways with C-3PO and R2-D2, leaving them with the Fuzzums on Dandelo.
Jann graduated from the Academy and was promptly stationed on Carfoom. Just a week after his graduation, Rebels attacked the outpost. Jann was shot in the back, resulting in paralysis from the waist down. After being fitted with a hoverchair, Jann was honorably discharged and returned to Tyne's Horky.
When Gundy passed away ten years later, Jann assumed control of the Gundarian Mining Company.

Tosh was often seen riding his 48 Roller wheel bike, a vehicle similar to that used by General Grievous.
A skilled fighter, pilot, and resourceful strategist, Jann transformed from a peasant on an insignificant planet into a royal advisor and military leader on Tammuz-an.
Jann Tosh was introduced as an action figure in 1985 by Kenner as part of their Star Wars Droids product line. These action figures were compatible in size with the other Kenner Star Wars action figures, but their design represented a distinct toy line.
Don Francks, the father of Cree Summer (the voice of Princess Kneesaa), voiced Jann in Star Wars Droids.
In the episode "The New King," set before the Battle of Yavin, Jann Tosh is depicted piloting an A-wing fighter, and at least one B-wing is visible in the hangar on Tammuz-an. However, neither starfighter was constructed until after that time. These vessels have since been retconned as R-22 Spearheads and H-60 Tempest bombers, respectively.
According to the brief character descriptions on the card backs of the Droids action figures, Jann is described as a teenager, whereas his current Databank entry on StarWars.com states that he is approximately 20 years old. The card back also suggests that Gundy and Jann have traveled to various worlds in search of treasure. If this information is considered canon, then Tyne's Horky is likely not Jann's birth planet.