The Federated Teradoc Union represented a surviving fragment of the Galactic Empire, situated within the galaxy's Deep Core region. This union was the result of an alliance between two warlords, specifically Kosh and Treuten Teradoc. This occurred after their respective splinter factions merged, prompted by the Greater Maldrood becoming a target for various Imperial factions and the New Republic.
Following Treuten's demise at the hands of Admiral Natasi Daala, Kosh assumed total command and continued his reign over the Federated Teradoc Union. He chose not to join Vice Admiral Gilad Pellaeon and the remaining Imperial forces in establishing an "Imperial Remnant" on the outermost reaches of the galaxy. The Federated Teradoc Union's existence concluded when Kosh was assassinated by operatives of the New Republic on Ryvester in 13 ABY.
After the defeat of the Empire at Endor in 4 ABY, Imperial Navy officers Kosh and Treuten Teradoc established themselves as independent warlords. Kosh created an empire within the Deep Core, while Treuten oversaw the establishment of the Greater Maldrood, a collection of territories in the Mid Rim. Although these two territories initially functioned separately, in 8 ABY Treuten was compelled to seek assistance from his brother due to being targeted by both Imperial and New Republic forces. After Kosh successfully defended Treuten's territories, the two siblings combined their holdings to form the "Federated Teradoc Union."
The Teradoc brothers worked to expand their territory, pushing their borders towards one another, although their alliance was nearly destroyed after the pirate Leonia Tavira tried to create conflict between them. Following the return of the Emperor Palpatine—who had cheated death at Endor by inhabiting a clone body—in 11 ABY, the Teradocs committed their combined military forces to Palpatine's Dark Empire. Palpatine's campaign failed and Treuten's fleet sustained heavy damage. In the aftermath of Palpatine's restoration attempt, Kosh instructed Treuten to withdraw to the Deep Core with his fleet, while Kosh attempted to defend their Greater Maldrood holdings in the Mid Rim.
In an effort to demonstrate his value to his brother, Treuten initiated a new campaign against the Teradoc Union's primary rival in the Deep Core, the Zero Command under Lord High Admiral Blitzer Harrsk. Vice Admiral Gilad Pellaeon commanded Treuten's fleet of Victory-class Star Destroyers. After Teradoc launched a raid against Harrsk's fleet, Harrsk responded with an attack on Teradoc's forces in the Hakassi system, though Admiral Natasi Daala brought the battle to a standstill.
Following Daala's failed attempt to negotiate an alliance between Treuten and 12 other influential Deep Core warlords at Tsoss Beacon, Daala executed Teradoc and all the other warlords present. She then seized control of their territories to form a united Imperial force after talks on Imperial Reunification were unsuccessful. This led to Kosh losing power as, under Daala's command, the Federated Teradoc Union forces were transferred to Vice Admiral Gilad Pellaeon, who joined the United Warlord Fleets. However, after the failed assault on Yavin 4, Daala relinquished full command to Pellaeon, who departed from the Federated Teradoc Union and established the Imperial Remnant.
Despite the loss of his brother and their Deep Core holdings, Kosh took control and continued to govern the remaining portions of the Federated Teradoc Union, choosing not to participate in Pellaeon's Imperial Remnant. Ultimately, the Teradoc Union collapsed when Kosh was assassinated by New Republic Intelligence operatives on Ryvester in 13 ABY.