The Eternal Alliance, alternatively referred to as the Galactic Alliance, represented a unified military front forged by the Outlander. Initially established as the Alliance Against Zakuul, its primary goal was to resist the once-dominant Eternal Empire and depose the despotic Emperor Arcann, and subsequently Empress Vaylin, his sibling. Following their triumph over both Arcann and Vaylin, the Alliance assumed control of the throne after vanquishing the remaining Imperial forces during the Battle of Zakuul. Subsequently, the Outlander restructured the Alliance, rebranding it as the Eternal Alliance. The Alliance absorbed all military resources of the Eternal Empire, including its massive fleet. Possessing the Eternal Fleet, the Alliance ascended to become the most formidable power within the galaxy.
In the wake of the Order of Zildrog's campaign waged against the Alliance, coupled with the destruction of the Eternal Fleet resulting from the use of the superweapon known as Zildrog, many members chose to return to their original factions.
In the aftermath of the Battle of Asylum, elements originating from both the Galactic Republic and the re-established Sith Empire came to the realization that the Eternal Empire was not impervious. The individual known as the Outlander spearheaded the movement, selecting the planet Odessen as its base. Odessen, a world unaffiliated with either the Force, proved to be an ideal location for fostering an alliance between the Republic, aligned with the light side, and the Empire, associated with the dark side. Consequently, a stronghold was erected at the base of a cliff, designated to serve as the Alliance's primary operational hub throughout the impending conflict.
Although the resistance movement commenced on a modest scale, it progressively evolved into a more substantial force, encompassing individuals from both the Sith Empire and the Galactic Republic. Noteworthy figures included Theron Shan, Lana Beniko, Major Pierce, Bey'wan Aygo, Hutt doctor Juvard Illip Oggurobb, and Hylo Visz, alongside numerous other specialists. As the Alliance solidified its position as a formidable entity, the Outlander was appointed as the commander of the organization, playing a pivotal role in augmenting its strength and orchestrating a series of strategic assaults against the Eternal Empire's Star Fortresses.
The Eternal Fleet became the Alliance's first target. Subsequently, collaboration with Kaliyo Djannis and Havoc Squad enabled the Alliance to pinpoint a hyperwave relay station situated beneath the Spire, responsible for transmitting directives to the Fleet. Kaliyo and Havoc Squad endeavored to infiltrate the Spire to access the relay station but were compelled to retreat, albeit after securing a datacore pertaining to the GEMINI droids that managed the Fleet.
Analysis of the datacore unveiled the existence of the GEMINI's template, GEMINI Prime, concealed within a factory located on Darvannis. To acquire the droid, the Alliance partnered with Mandalorians to lay siege to the factory. Following the acquisition of the Prime, SCORPIO ascertained that GEMINI Prime possessed the capability to seize control of the Eternal Fleet if integrated into the captain's chair of one of the vessels. The Commander personally spearheaded a boarding party to commandeer a solitary ship, only for SCORPIO to betray the Alliance, assuming control of Zakuul and the majority of the Eternal Fleet while exposing Odessen's location to Arcann.
With their location compromised, the Alliance mounted a defense of their base, with only the Gravestone confronting Arcann and the Eternal Fleet vessels under his command. The Outlander led a boarding party onto the Eternal Flagship to defeat the Emperor and disable the Flagship, even as SCORPIO seized control of Arcann's ships to eliminate both her adversaries simultaneously. The Commander successfully defeated Arcann, leaving him for dead, only for his mother Senya Tirall to betray the Alliance to rescue her son and flee the system. The Gravestone subsequently annihilated the Eternal Fleet, averting the Alliance's destruction. In the wake of their triumph over Arcann, Republic and Imperial forces from across the galaxy defected to enlist in the burgeoning Galactic Alliance.
Despite Arcann's defeat, the Alliance encountered an even more lethal adversary in his sister Vaylin, who ascended to the throne with SCORPIO as her advisor and initiated a galaxy-wide search for her family. Eventually, the Alliance intervened in the defense of Voss when the Eternal Fleet launched a full-scale assault. The battle concluded when the Sith Empire intervened, compelling the Fleet to retreat.
In light of Empress Darth Acina's assistance, the Commander traveled to Dromund Kaas to deliberate on an alliance against Zakuul. However, shortly after their arrival, both the Commander and Empress were reportedly killed in a shuttle crash. Subsequently, former Republic Supreme Chancellor, Leontyne Saresh, offered to assume leadership of the Alliance. Aygo advocated for her dismissal, but the lower-ranking troops, uncertain of the Alliance's future without their leader, desired to hear her out. However, just as Saresh commenced her address, the Commander reappeared on Odessen, alive and well, having survived an assassination attempt orchestrated by the GenoHaradan, dispatched by Saresh in her endeavor to seize control of the Alliance, thereby thwarting her attempted coup.
The Alliance later responded to a distress signal from Captain Koth Vortena aboard the Gravestone, which had been boarded by Vaylin and SCORPIO. The Alliance fleet re-engaged the Eternal Fleet while the Commander and their inner circle attempted to reclaim the Gravestone. Regrettably, after the Commander deactivated the quantum bomb aboard the Gravestone, SCORPIO seized control, transporting it and the Eternal Fleet to their homeworld of Iokath. To the Alliance's relief, the Commander managed to survive Iokath, returning to Odessen with the Gravestone. The Alliance promptly initiated upgrades to the Gravestone, utilizing datafiles recovered from Iokath.
With Vaylin having regained control of the Eternal Fleet from SCORPIO, the Alliance resolved to terminate her reign by collaborating with local Zakuulan rebels led by Indo Zal. The Commander, accompanied by Theron Shan and Lana Beniko, infiltrated the Grand Festival of Empress Vaylin in an attempt to assassinate Vaylin. The operation was complicated when Arcann independently launched an assault on the Palace of the Eternal Dragon with a contingent of loyalists, ultimately resulting in Vaylin's disgraced flight from Zakuul.
The Commander subsequently pursued Vaylin to Nathema, where the Empress managed to overcome her mental conditioning before initiating a full-scale assault on Odessen. The Alliance once again withstood the Eternal Empire's onslaught before the Commander succeeded in killing Vaylin, causing the Eternal Fleet to retreat and her ground forces to surrender. The battle resulted in substantial casualties for both the Alliance and the Eternal Empire, but these losses would shift the tide of the war, rendering an Alliance victory almost certain.
Regrettably, lacking a master, the Eternal Fleet commenced a rampage across known space, intent on eradicating all life. With no alternative, the Alliance fleet, spearheaded by the Gravestone, journeyed to Zakuul, where the Fleet was bombarding the planet and safeguarding the Eternal Throne. While the Alliance kept the Fleet occupied, the Commander attempted to access the Throne from the surface. Once the Commander assumed control of the Throne, the Fleet was pacified.
With the Eternal Fleet under control and the Royal Family of Zakuul vanquished, the Commander announced to the entire galaxy the dissolution of the Eternal Empire and the Alliance's transformation into the Eternal Alliance as a new galactic power. However, despite this triumph, the Republic and Sith Empire initiated war preparations, and rogue factions throughout the galaxy launched their own uprisings in response to the Eternal Alliance's ascent to power.
When radiation levels decreased to sustainable conditions, Lana Beniko scouted the planet Iokath for a supposed superweapon, later confirmed to be real and a massive threat. However, before she could investigate further, a Republic scout fired upon and destroyed her probe droid, and then engaged unknown Imperial scouts. While the two battled, the Eternal Alliance set up a massive base camp, heavily defended, with the Eternal Fleet overhead, only with its weapons deactivated. Upon the Alliance Commander's arrival, the Eternal Alliance found itself embroiled in a newly spawned war on the planet between the long-standing adversaries of the Galactic Republic and Sith Empire. Concentrating on the primary objective, the Commander gathered allies near a throne harboring the secrets of Iokath. However, the opposing power's leader reached the throne first, attempting to unleash the superweapon, but they were overwhelmed by Iokath's hidden power and perished while attempting to harness it.
While a tragic moment, this freed the Eternal Alliance (as well as Sith and Republic) fleet. The Commander then ordered Eternal Fleet ships to fire upon the superweapon revealed to be a droid named Tyth, not before it firing and destroying an Eternal Fleet warship first. The weapon retreated underground, where Alliance forces closed in, awaiting orders. The Alliance Commander formed a special operations team and engaged Tyth soon after, destroying it. But the Commander did gain a power cell from Tyth, and gained the ability to create more droids like him for the Alliance, something both the Republic and Empire feared but could not prevent, being preoccupied with the quarrel against each other.
Shortly after the battle on Iokath, Theron Shan and Lana Beniko informed the Alliance Commander that the traitor was on Umbara attempting to smuggle Adegan crystals. With Theron and Lana at their side, the Commander raced to Umbara to catch the traitor. The Commander hijacked a moving train and fought their way to the front of it. The traitor then revealed himself as none other than Theron Shan. Theron explained his motives for why he betrayed the Alliance and desired to topple it. He told the Commander how he thought the Alliance would be no different than the Eternal Empire. Theron escaped the train on a speeder while the Commander and Lana jumped before the train could crash.
Stranded in the Umbaran wilderness, the Commander and Lana fought against local Umbarans and wildlife while also collecting Adegan crystals to enhance the Alliance's weaponry. Eventually, Theron escaped and the Commander, along with Lana, fought against an Umbaran Spider Tank. Back at the Alliance Base, the Commander was informed by Lana that she had her agents looking for Theron and assessing how much damage he inflicted from the inside. The Commander then sent a galaxy-wide message to Theron. Meanwhile, a mysterious figure welcomes Theron to the Order via holomessage.
The Alliance Commander received a message from the Chiss Ascendancy about Theron Shan taking refuge with a rival house, House Inrokini. The Ascendancy, officially, can't act on this, but they secretly supported the Alliance. The Commander, with the help of Raina Temple, landed on Copero. They infiltrated House Inrokini, and after defeating the powerful Guardian Droid, and Syndic Zenta, they learned that Theron was trying to locate a powerful superweapon that could lay waste to the Alliance. Valss, a powerful Chiss Force-sensitive ally of Theron's, distracted the Commander, while Theron escaped. Back at the Odessen base, the Commander was given the secret support of the Ascendancy, and Temple would stay as a liaison.
Following the Order of Zildrog conflict, the Eternal Alliance prospered on Odessen until stories of the Quesh riots and Wild Space skirmishes arrived. The signals of a renewed conflict between the Sith Empire and Republic prompted Lana Beniko to ask the Commander to join forces with one of the major factions. The Commander chose to support the Republic and traveled to Nar Shaddaa to meet Jonas Balkar and arrange it.
Soon after, back on Odessen, the Commander was contacted by the Republic Military's General Ardinondu Dipolus Daeruun who requested the Commander's aid on the planet Ossus. General Daeruun had discovered that a hidden Jedi settlement led by Jedi Master Gnost-Dural was being threatened by Imperial discovery and couldn't assemble the needed forces in time to prevent the colony's destruction. The Commander traveled alone to Ossus to support the evacuation, pending the Imperial invasion of the planet.
In its initial phase, the Alliance's military comprised volunteers hailing from the Sith Empire, Galactic Republic, Jedi Order, Sith, and numerous other opponents of the Eternal Empire. Military Operations, the military arm of the Alliance, was commanded by former Republic Admiral Bey'wan Aygo, but remained under the direct supervision of the Alliance Commander at all times.
Initially, the Alliance Fleet consisted of privately-owned vessels donated by supporters. Following the first Battle of Odessen, Thranta-class and Terminus-class cruisers deserted their original factions to join the Alliance. The ancient frigate named the Gravestone served as the Navy's flagship, captained by Koth Vortena.
Following the Battle of Zakuul, the Alliance Navy experienced significant expansion with the Eternal Fleet under the Alliance Commander's command, establishing the Eternal Alliance as the possessor of the galaxy's most formidable Navy. With the complete absorption of the Eternal Empire, many regarded the Eternal Alliance as the dominant force in the galaxy, surpassing even the Galactic Republic and Sith Empire.
As a consequence of the Commander's Mission to Nathema, the Alliance Navy's strength diminished substantially due to the destruction of the Eternal Fleet and the Gravestone, thus reducing the alliance's overall military prowess.
The Alliance Army encompassed former Republic and Imperial citizens and soldiers, Jedi and Sith, along with Voss Mystics to ensure cooperation between the long-standing adversaries, smugglers and pirates of diverse backgrounds, Mandalorians, independent forces ranging from farmers to mercenaries, and later Zakuulans. With the majority of Zakuul's armed forces joining the Eternal Alliance, the organization's initial members harbored prejudices towards their former enemy. However, over time, Zakuulans demonstrated their commitment to the Alliance and proved that they did not necessarily endorse their Emperor's actions. Given the Eternal Empire's strong emphasis on military supremacy, the Zakuulans significantly enhanced the Alliance's power and influence in nearly every aspect. Furthermore, numerous Knights of Zakuul joined, along with the entire force of Skytrooper droids – and their manufacturing facilities – further augmenting the newly-established superpower.
The Alliance Army also maintained a specialized Recon Task Force, often led by the Alliance Commander themselves. This unit comprised four highly skilled, stealthy agents capable of neutralizing potent and hazardous threats. This squad was known to be deployed ahead of a main Alliance force. Although part of the Army, they were directed by Alliance Intelligence.
In Star Wars: The Old Republic: Onslaught, the player is presented with the option to integrate the Alliance into either the Republic's Task Force Nova or the Empire's Hand, contingent on the player's original faction and whether they have pursued the loyalist path. Alternatively, the player can opt to maintain the Alliance's independence, which serves as the default choice for players who have followed the saboteur path, as they would not be invited back regardless of the outcome.