The Eternal Fleet was an ancient armada created on the planet Iokath. It was operated by sentient droids, and controlled through the Eternal Throne. The Eternal Flagship was a capital ship that served as the flagship of the Eternal Fleet. It was utilized first by the Eternal Empire, and later by the Eternal Alliance.
The Eternal Fleet was an immense fleet composed of alien battlecruisers of an unknown design which were roughly equal or greater in length than that of a Terminus-class destroyer utilized by the Sith Empire. They were highly advanced, possessing cloaking technology, and operated by sentient droids; in combat they were able to overwhelm almost any other vessel. They were very fast, as only vessels retrofitted with Isotope-5 were capable of outrunning them, although Republic and Imperial ships weren't able to compete with them in combat.
These capital ships carried drop ships that could perform in both atmosphere and space combat to land troops, along with deploying starfighters. They also possessed Skytrooper boarding pods designed to penetrate the hull of an enemy vessel, allowing their droid occupants to cause damage throughout multiple sections of a targeted ship.
By lining up in a precisely calibrated array formation, the fleet could release a powerful combined attack. If one of the arranged vessels was destroyed while charging, they would all violently explode, destroying anything within the blast radius.
The Eternal Fleet was built many centuries ago before the time of Valkorion by an unknown race on the planet of Iokath. The fate of the Fleet's builders is unknown but their legacy would live on. Its first known action was in the annihilation of all life in Wild Space. It spread across Wild Space and conquered almost every inhabited world within the region, including Zakuul. They were finally defeated by a mysterious vessel known as the Gravestone, a massive alien warship that countered the Eternal Fleet's might. Outfitted with specialized weapons designed to take out multiple targets at once, the Gravestone destroyed whole sections of the fleet with a single shot. The Eternal Fleet was finally defeated over Zakuul, where it was deactivated and hidden away. The Gravestone landed in the swamps of Zakuul, where the crew scuttled it and hid it away.
Rumors would persist of this unstoppable fleet until they finally reached the ears of Valkorion and came to the last place it was said to be: Zakuul. It was for this reason that he chose the world to house his new Empire; once he ruled Zakuul, Valkorion used the power of the Scions of Zakuul to locate the fleet. A little more than a century before 3636 BBY the Eternal Fleet was brought back into operation this time under the control of the Eternal Throne. Valkorion used the fleet to carve out a sizable area of Wild Space with the ships being kept close to the capital world being cloaked until needed. The fleet would see little use from that point on save a few ships collecting tributes from the worlds underneath the Empire's sway, it would not be until a century later that the ships saw true combat once more. Arcann and Thexan, twin princes of the Eternal Empire attempting to gain their father's admiration proposed on using the fleet to test the strength of the Galactic Republic and Sith Empire to which Valkorion agreed.
In a lightning strike, the fleet along with the princes and their Knights of Zakuul attacked the outlying planets of both governments first those in Wild Space then deeper until even Korriban was attacked leaving only devastation in their wake. Sometime after this event, a combined Republic-Imperial fleet led by Darth Marr would have the First skirmish with the Eternal Fleet, resulting in the capture of both the Sith Lord and the Outlander, which would culminate in the death of Emperor Valkorion, causing his son Arcann to assume the throne and to begin the Eternal Empire conquest.
In 3631 BBY, the Eternal Fleet attempted to thwart the Outlander's escape from Zakuul, but the Outlander and their allies found the Gravestone, which destroyed more than two dozen ships in a single shot, enabling the warship to bypass the blockade. Later, the Eternal Fleet saw action over Asylum. Despite the Gravestone's omnicannon being non-operational, the ship was able to destroy one Eternal Empire ship with its blaster cannon before escaping into hyperspace.
The Eternal Fleet later destroyed five planets in five separate sectors on Arcann's orders in an effort to force anyone to come forward with the whereabouts of the Outlander.
The Alliance later attempted to commandeer a lone warship in hopes of plugging GEMINI Prime into the captain's chair and take over the entire GEMINI network. However, SCORPIO secretly betrayed the Alliance, granting the GEMINI captain free will and faked her own destruction. While Arcann was away from Zakuul, SCORPIO's intelligence took over the Eternal Throne and the fleet, save for the detachment that Arcann took with him. The Alliance suspected that before GEMINI Prime shut down, she managed to protect Arcann's support ships from SCORPIO.
Arcann later brought his support ships to attack Odessen after SCORPIO leaked the location of the Alliance base. The planet was defended by only the Gravestone, which cleared a path for the Outlander's shuttle to board the Eternal Flagship. But some time after the Flagship's weapons and shields were sabotaged by the boarding party, SCORPIO managed to take control of all the Eternal Fleet ships and ordered them to fire on the Flagship. As the Flagship is vacated, the Eternal Fleet ship formed up and began charging a powerful energy attack. The Gravestone fired its omnicannon at the Flagship, the chain attack disrupting the Fleet's attack. The Flagship then exploded, wiping out the entire Fleet and saving the Alliance from destruction.
With the entire Eternal Fleet under her control, SCORPIO accomplished her main objective: to grant the GEMINI units free will. Soon afterwards, some Eternal Fleet ships left Zakuul to explore the galaxy. SCORPIO then yielded the Eternal Throne to Vaylin, promising that she and her "children" would support her.
The Eternal Fleet later invaded Voss after Vaylin discovered her mother Senya Tirall and Arcann were on the planet. The Alliance responded to the attack and engaged the Fleet. Ultimately, the GEMINI droids chose to retreat when another fleet sent by the Sith Empire arrived and destroyed a few of their ships, an action which served to anger the Empress.
SCORPIO, still operating under her own agenda, convinced Vaylin to hijack the Gravestone. Three Eternal Fleet ships were sacrificed in a ploy to lure the Gravestone into a trap, in which Vaylin and SCORPIO boarded the frigate in a cargo ship. The Outlander brought the Alliance fleet to stop Vaylin and SCORPIO and began battling the former for control of the Gravestone. While the organics were distracted, SCORPIO gained control over the Gravestone and discovered the location of Iokath in its databanks and ordered the Fleet to travel there.
Upon entering the superstructure, the Fleet was hit by a planetary superweapon controlled by ARIES, the only sentient droid left on the planet, who impounded the Fleet at a docking spire and removed the crews and scattered them across the planet to place in impossible tests to see who was worthy of inheriting Iokath. Vaylin managed to rally her followers to liberate the Fleet, releasing half of the armada from the spire, while the other half were towed with tractor beams. However, one Eternal Fleet ship was destroyed upon colliding with Iokath's planetary energy shield, so Vaylin ordered the Fleet to track down and destroy ARIES's base of operation. After SCORPIO lowered the planetary shield, the GEMINIs desired to escape, as ARIES had prepared the superweapon to fire lethally. Annoyed with GEMINI's free will, Vaylin learned from a damaged Purifier droid she captured that he can reset GEMINI to default protocols, making them all obedient again. Five Eternal Fleet ships then pursued the Gravestone, while the rest fled the planet and returned to Zakuul. Vaylin then brought the Purifier to the Eternal Throne, connecting him to the GEMINI frequency, resetting all the droids to default settings, and tested their renewed obedience by ordering one ship to destroy another.
When the Grand Festival of Empress Vaylin was crashed by both the Outlander and Arcann, Vaylin ordered the Fleet to fire on the Palace of the Eternal Dragon in an attempt to destroy both her enemies.
After Vaylin had broken her mental conditioning, she led the Fleet in an even more devastating attack on Odessen. The Fleet ultimately retreated after the Outlander slew Vaylin.
Without a master sitting on the Eternal Throne, the GEMINI droids reset to default programming and the fleet reverted to its primal instinct: extermination. The Eternal Fleet went on a rampage throughout the galaxy, assaulting worlds such as Coruscant, Dromund Kaas and Zakuul in an effort to eradicate all life in the galaxy.
When Vaylin was defeated, and the Outlander secured the Eternal Throne and absorbed the Eternal Empire into a new Eternal Alliance, the Eternal Fleet became the navy and effectively largest threat the Alliance had at its disposal. It was then used as a leverage between the smaller Alliance and its Republic and Imperial counterparts. Ironically, the fleet was the main reason of tension between the three powers, with leaders fearing the Outlander's unchecked power as commander of the Eternal Throne and its fleet.
The fleet would mainly be used for supplies runs between the Alliance and other galactic powers. It would not be until the War on Iokath that the Fleet would be used in combat for the Eternal Alliance's first military conflict. Upon arriving in Iokath's orbit, the Fleet mysteriously went offline, which Theron Shan theorized was due to the planetary superweapon. The Fleet later came back online in time when the superweapon, revealed to be the enormous droid Tyth, awoke. Tyth unleashed his power, destroy one Eternal Fleet ship before the armada opened fire on the superweapon at their master's command, forcing Tyth to retreat.
Following the events which transpired on Umbara and Copero and the apparent treachery of Theron Shan the Eternal Alliance found itself in the crosshairs of an organization known as the Order of Zildrog, under the leadership of former Horizon Guard member Vinn Atrius. This group of fanatics sought to destroy the Eternal Alliance by supposedly resurrecting the Dragon God which is their namesake. The Alliance soon discovered that this plot revolved around the world Nathema, a planet left lifeless by Valkorion when he still went under the guise of Vitiate. The Alliance Commander and Lana Beniko deployed planetside to find and stop the Order of Zildrog before they could carry out whatever it was they had planned. On Nathema they met up with Theron Shan, who as the matter fell had feigned defection to the Order in an effort to learn what Vinn Atrius was trying to do and feed information to The Eternal Alliance. Together the trio broke the defenses set in place to bar them and found themselves face to face with Atrius himself, in what they discovered was Zildrog's core.
The Dragon God of Zakuul was an advanced AI in much a similar vein to the Zakuulan pantheon, which turned out to be constructs fabricated by the builders of Iokath. Except Zildrog's body as it were, was the Gravestone itself. Upon activation, Zildrog seized control of the ship and employed its Omnicannon to utterly annihilate the Eternal Fleet in orbit above Odessen, bringing an end to the armada once and for all.