Kosh was the younger brother of Treuten Teradoc. From an early age he shared a fierce and mutual rivalry with his brother. They chased the same goals of fame, wealth and power. inspired by holodramas and growing up under the Empire both enlisted in the imperial officer Academy for the Imperial Navy. kosh was not physically impressive, given to a paunch and relatively short stature he was however gifted in strategy. While not considered overly brilliant he was still sharp and adept. After a relatively uneventful career yet moderately fast promotion to Commander he received command of an Imperial Star Destroyer- a vessel twice as large and prestigious as his brother's Victory class command. While he commanded a larger ship, his brother commanded far more vessels and rose higher in rank. It's not known if Kosh achieved the rank of Admiral before Endor, but what is known is that kosh chose to strike out on his own in the Deep Core rather than remain under his brother Treuten's command when he went Rogue. His rivalry with Treuten would not let him suffer to serve beneath his then more successful older brother. Arriving in the Deep Core with his ISD and a small fleet of support ships Kosh quickly discovered it was anything but a safe haven. In the Deep Core Warlords Harrsk, Delvardus, Prentioch and a dozen other smaller Warlords all fought and strove for dominance. However rather than die in this hostile free for all-Kosh FLOURISHED. He abstained from the overindulgence of his brother, developed new tactics, became flexible as a commander and opportunist. He won time after time against long odds becoming a master strategist through experience and commanding a loyal and elite force that grew with each passing year as he bested rivals, convinced forces to defect to him and absorbed Imperial remnants fleeing to the Deep Core from the rest of the Galaxy. By 4.5 years after Endor Kosh had established a tiny yet powerful mini Empire that could hold its own against much stronger opponents. This was when he received a startling message from Treuten-his brother needed help badly. Kosh might well have laughed and left Treuten to his fate but the idea of being his brother's savior, lording it over him and absorbing much of his brothers holdings to boot to bolster his own Deep Core holdings was too good to pass up. Kosh took command and in a series of brilliant rear guard actions stabilized the rapidly disintegrating Greater Maldrood. With the situation somewhat stable now Kosh and Treuten entered into a long term military and civil alliance joining their holdings together into the Federated Teradoc Union. While Treuten held more forces and territory, Kosh held more elites and experience. Together they prospered while the NR focused on Thrawn. Then Palpatine returned and called for the Teradoc's to join with him in an all out assault on the NR. Kosh was hesitant to commit their still recovering forces to a major campaign but Treuten threw his full support behind Palpatine to try and recover his lost territory and dominant position compared to Kosh. The results were disastrous. Treuten suffered appalling losses in the campaign and afterwards was driven to near ruin by NR forces. Kosh, disgusted with Treuten's pride filled failures he sacked his brother from command of the Mid Rim forces and sent him to the relatively secure Deep Core holdings with his forces while he tried to salvage what was left of the Mid Rim.
Treuten however descended to even further levels of gluttony and depression and started a war with Harrsk bleeding his forces yet further. Shortly after this Treuten was killed at Tsoss Beacon by Admiral Daala and his forces absorbed by her united empire.
Kosh when hearing this in the Mid Rim was struck-not by rage at Daala, not by anger at the loss of his Deep Core Holdings and forces...but by sadness and regret. He realized he and Treuten had wasted their lives fighting. Rather than enjoying the family they were they had competed in bitterness and anger their whole lives. Kosh likely blamed himself for his brother's death as Treuten's last major campaigns had been launched to try and impress kosh or show him up in their rivalry-and Kosh had not dissuaded it. With his vastly reduced forces, tiny holdings and surrounded by the NR, Kosh might well have realized he was doomed and lost a lot of the will to live. he waged no campaigns after Treuten died and barely defended his shrunken borders, he stayed away from the front now, remaining in his personal fortress alone and ever more isolated in the past. He was eventually assassinated by Wraith Squadron when they disguised a pressure bomb in a gem he had sought since childhood with Treuten. Kosh died clinging to the last memento of his childhood with his brother. He had lived and died from the rivalry and link to his brother.