Odessen, a planet deeply connected to the Force, resided in the Wild Space near the Unknown Regions. This world, characterized by vast oceans and mountainous landmasses, possessed a temperate climate and hosted diverse wildlife within its wooded landscapes. It was an insignificant and isolated planet, chosen by Satele Shan as her place of retreat following the Grand Master's failure to protect the Galactic Republic from the Eternal Empire conquest. During the war against Zakuul, Lana Beniko selected Odessen to serve as the central hub for the Alliance resisting the Eternal Empire of Zakuul. This Alliance base was secretly established in the wilderness, but its location was eventually exposed by SCORPIO to Eternal Emperor Arcann, prompting him to launch an assault on the Alliance with his Eternal Fleet in what became known as the Battle of Odessen. Despite the attack, the Alliance emerged victorious without any losses and further reinforced Odessen's defenses, ensuring their continued resistance against Arcann's sister Vaylin. Undeterred, Vaylin launched another assault on Odessen, resulting in intense combat both on the ground and in orbit, but the Alliance once again prevailed. Following the Alliance's triumph over Zakuul and its transformation into the new Eternal Alliance, Odessen was designated as the capital of this new governing body.
Located in the remote reaches of Wild Space, Odessen was a largely untouched world during the early Inter-Sith Wars period. Its surface was predominantly covered by oceans and seas, accounting for over half of its total area. The landscape was abundant with flourishing vegetation, featuring towering forests that thrived on the slopes of its mountain ranges. The shade stalkers, a species of predatory pack hunters, were the only known indigenous inhabitants of Odessen. As a potent Force nexus, Odessen resonated strongly with the Force, a phenomenon noted by numerous Force-sensitives. Intriguingly, the Force on Odessen was not inclined towards either the dark or the light side. This unique Force presence on Odessen contributed to accelerated evolutionary cycles in both native and introduced species.
The thick, scaly hides of the shade stalkers suggested that they had not always been predators, and their apparent lack of consumption puzzled researchers as to how they sustained themselves. At some point, jurgoran from Dromund Kaas were introduced to Odessen, where they evolved bioluminescent scales and a reflective hide to adapt to the low-light conditions, leading to their classification as a new cave jurgoran subspecies. Notably, when Doctor Juvard Illip Oggurobb introduced several new species to Odessen in 3631 BBY, he observed significant evolutionary changes in less than a year. The sleen from Dromund Kaas exhibited a noticeable increase in agility and reaction time, the makrin from Makeb altered their skin texture to blend with the local forests, and the Tarisian bogstalker developed a plasteel-like barb on its tail, leading to its reclassification as the steel-tailed stalker.
Following the Galactic Republic's surrender to the Eternal Empire of Zakuul in 3636 BBY, Satele Shan, the Grand Master of the Jedi Order, sought refuge on Odessen due to its unique properties within the Force. After landing her starship in the wilderness, the Jedi used her lightsaber to clear an area in the forest and establish a small camp. She resided there for several years, accompanied only by the Force ghost of Darth Marr. In 3631 BBY, both of them sensed the reawakening of the Sith Emperor Valkorion in a new physical form and began preparations for the arrival of the Commander, who unknowingly became Vitiate's latest host.
Lana Beniko, the former Sith Intelligence Minister, rescued the Outlander from Zakuul and initiated a war against Zakuul, searching for a suitable location to establish a permanent base. Guided by the Force, she felt drawn to Odessen. Following the Battle of Asylum, which served as a rallying point for those opposing the Eternal Empire, Lana contacted her extensive network of contacts from the Sith Empire, the Galactic Republic, and the criminal underworld, summoning them to Odessen. Lana and the Outlander arrived on Odessen aboard the Gravestone, accompanied by Senya Tirall, SCORPIO, T7-O1, Koth Vortena, and his crew, including Len Parvek, Ralo, and Tora. Lana's contacts were already present, and together, they laid the groundwork for an Alliance dedicated to resisting the tyranny of the Eternal Empire, with the Outlander as its Commander.
Former criminals and law enforcement officers, soldiers from the Empire and the Republic, and even the Sith and the Jedi, collaborated to construct the Alliance base on a cliffside, incorporating extensive surface defenses and an expanded network of underground caves. Large landing pads and docking stations were built to accommodate Alliance starships, including the flagship Gravestone. Shortly after the base's completion, a planetary shield was erected to protect the base and the surrounding area from aerial bombardment, ensuring that the Eternal Fleet could not obliterate the Alliance with a single, devastating attack. Doctor Oggurobb spearheaded the shield's construction, and during the initial stress tests, it withstood the bombardment from Fleet Admiral Bey'wan Aygo's most powerful battleship.
The Alliance launched several daring attacks against the Eternal Empire, attracting new recruits and volunteers. When the Alliance planned an attack on the hyperwave relay station on Zakuul, Beniko suggested that the Commander consult Valkorion for insights on infiltrating the facility he had built. The Commander agreed and sought him out in a secluded area of Odessen's wilderness, but Valkorion refused to share any secrets. Instead, Valkorion revealed that he had lured the Commander to the wilderness to experience death alone and overpowered his host, feigning departure to attend to other matters while rendering the Commander unconscious. Satele Shan discovered the Commander's unconscious body and transported them to her starship, which remained parked at her camp.
Upon awakening, the former Grand Master and the ghost of Darth Marr provided the Commander with insights into Emperor Arcann and his Knights of Zakuul, who held a different perspective on the Force than the Jedi or Sith. Following their guidance, the Commander gathered items from around the valley before venturing into a dark cave, where they created a new weapon infused with pure Force energy. At Satele's direction, the Commander proceeded to a nearby oasis for their final trial, where they killed two young jurgorans, angering their mother. After the Commander resolved the confrontation with her, Marr and Satele announced their departure from Odessen, having received a call from the Force, and the Commander returned to the Alliance base.
During an attempt to seize the Eternal Fleet, SCORPIO betrayed the Alliance and claimed control of the Eternal Throne. She left a significant portion of the Eternal Fleet seemingly under Arcann's command and manipulated her enemies into destroying each other by revealing Odessen's location to Arcann while simultaneously warning the Alliance of his impending arrival. As the Eternal Fleet, led by Arcann's Eternal Flagship, entered the system, the Alliance leadership boarded the Gravestone and engaged them in orbit in the Battle of Odessen. Lana determined that the only way to ensure the Alliance's safety was to destroy the Eternal Flagship, and, along with Senya Tirall, accompanied the Alliance Commander to infiltrate it. Senya separated from the others to locate her daughter Vaylin, while Lana and the Commander confronted Arcann on the bridge, only to discover that the Eternal Fleet had turned against Arcann and was targeting the flagship to eliminate both him and the Commander.
Upon reaching the bridge, Beniko remained behind to confront a squad of Zakuulan Knights, allowing the Commander to face Arcann alone. The Commander defeated Arcann and crushed him under debris. As the flagship began to disintegrate, Beniko and her team commandeered a Zakuulan shuttle, while the Commander narrowly escaped in a Zakuulan starfighter. En route back to the Gravestone, Senya contacted them, revealing that she was with Arcann aboard his personal shuttle, taking her son into hyperspace to redeem him. Theron Shan then fired the omnicannon on the Eternal Flagship, creating a massive explosion that obliterated the present portion of the Eternal Fleet and secured the Alliance's victory. The Battle of Odessen became the rallying point the Alliance needed, bolstering its ranks and providing the capability to repel future invasions.
At one point, the Shroud, a notorious criminal mastermind, infiltrated the Alliance base and planted bombs throughout it, but the bodyguard droid HK-55 thwarted his plan before he could detonate them and cause any damage. When the Alliance Commander went missing and was presumed dead on Dromund Kaas, Leontyne Saresh, the former Republic Supreme Chancellor, arrived on Odessen, seeking to seize control of the Alliance. Saresh was delivering a speech to Alliance personnel when the Commander, who had survived the assassination attempt ordered by her, interrupted her. The former Chancellor attempted to flee, but Lana intercepted her, allowing the Commander to decide whether to imprison or eliminate the Twi'lek.
Following Arcann's departure, his sister Vaylin assumed the role of Empress of Zakuul. After breaking free from her mental conditioning on Nathema, she launched another assault on Odessen, determined to destroy the Alliance once and for all. The attack occurred while the Gravestone was undergoing upgrades from Iokath in the dry dock. The Alliance fleet engaged the Eternal Fleet in Odessen's orbit, but without the Gravestone, they were unable to prevent Zakuulan ground forces from landing. The Eternal Empire deployed a vast number of troops and ground vehicles to Odessen's surface, with World thrashers clearing landing zones in the wilderness, Zakuul Hovercrafts deploying battalions of troops, and Eternal Empire Walkers providing heavy fire support.
Zakuulan troops focused on capturing the Gravestone, but the crew sealed all entrances and worked frantically to complete the upgrades and get the ship airborne. Intense fighting erupted around the Alliance base, with former Republic and Imperial soldiers fighting alongside each other against the Eternal Empire forces. Qyzen Fess led the Trandoshan Warstalkers, while Torian Cadera joined a group of Mandalorians to reinforce Bey'wan Aygo's position. Voss Mystic Sana-Rae and her students attempted to defend the Gravestone, but they were forced to retreat when the enemy deployed heavy artillery nearby. Vette volunteered to disable the artillery guns using a rocket launcher provided by Doctor Oggurobb, who was busy securing the research inside his base.
The Alliance Commander, Theron Shan, and Lana Beniko returned from their mission to Nathema while the battle was already underway. Theron dropped Lana and the Commander off near the base and went to infiltrate the enemy lines and cause chaos. The Commander and Lana commandeered a walker from Vaylin's forces to clear a path to the Gravestone, where enemy troops had begun breaching the ship's hull. However, the crew completed the upgrades just in time and launched into space to confront the Eternal Fleet. The Commander decided to lure Vaylin to the surface of Odessen and used a holocomm to provoke her into a direct confrontation. By this point, Torian was the only survivor of his unit, cut off by an enemy ambush, while Vaylin's forces had pinned down Vette on another part of the battlefield.
The Commander made the difficult decision to save one of their allies first, arriving just in time to eliminate the enemy forces surrounding them. The Commander then rushed to aid the other combatant, but Vaylin had reached them first, taking them prisoner and sending the Commander coordinates for a direct confrontation on the Alliance landing platform. The Commander rushed back to the Alliance base, where Oggurobb's position was being overrun, while Gault Rennow and Bowdaar had barricaded themselves inside the Alliance headquarters. The southern perimeter of Aygo's defense had been breached by enemy forces, who had also pushed back Sana-Rae and her students, requiring Aygo to send reinforcements. Vaylin awaited the Commander with a host of skytroopers and Horizon Guards, holding the prisoner at her mercy. After Valkorion appeared before his daughter, declaring her unworthy of the Eternal Throne, she contemptuously threw her hostage at the Commander, attempting to use the Force to snap their neck.
The Commander engaged Vaylin and defeated her in combat, but Vaylin unleashed a massive Force Storm, threatening to destroy the entire Alliance base, forcing the Commander to strike her down. With their will to fight broken, the Eternal Empire soldiers began surrendering en masse, while the Eternal Fleet retreated. The Alliance then traveled to Zakuul, claimed the Eternal Throne, gained control over the Eternal Fleet, and established dominance over what remained of the Zakuulan military. The Alliance reorganized itself into the new Eternal Alliance, which continued to operate from Odessen even after evolving from a small insurrection into one of the major galactic powers. The Eternal Alliance relocated the Eternal Throne from the Spire of Zakuul to Odessen, where it was installed in the Alliance base, enabling the issuance of new orders directly to the Eternal Fleet.
Odessen makes its debut in Knights of the Fallen Empire in Chapter IX: The Alliance, becoming the location of the player's new Alliance headquarters, which is featured in nearly every subsequent story update. Unlike most planets in the game, Odessen is not accessible for exploration outside the Alliance base, and most of the events on the planet occur within instanced areas rather than in an open-world environment. Odessen also serves as a hub for gameplay activities, housing Galactic Trade Network terminals, Priority Mission consoles, and entrances to several flashpoints. An "Odessen Proving Grounds" warzone was also introduced as a player-versus-player map.
At the conclusion of the Objective Meridian flashpoint in the Onslaught expansion, players are given the option to align Odessen with either the Galactic Republic or the Sith Empire, or to maintain its independence, depending on their factional allegiance. For those who side with the Republic, Odessen would gain its own Senator.