Dominus Ghaul's History
Dominus Ghaul was the self-proclaimed ruler of the Cabal Empire, after the exile of its previous Emperor Calus. Upon receiving the distress call sent by the Skyburners during the Taken War, Ghaul traveled to the Solar System with his Red Legion with the goal of claiming the Traveler and its Light for himself.
He successfully carried out a surprise attack against the Last City, capturing The Speaker, destroying the Tower, and severing the Guardians' connection to the Light by isolating the Traveler within a containment device.
The Ghost Primus
Ghaul was born a runt, and was abandoned at birth to die of exposure according to Cabal custom. Instead, he was found by The Consul, a disgraced scholar and aristocrat of the Praetorate, who decided to raise, befriend, train, and teach Ghaul in the hopes that he would one day overthrow Emperor Calus. In particular, the Consul taught Ghaul of the Traveler and instilled in him a belief that the Cabal deserved its power by right. Ghaul knew how the Consul was using him and accepted it as a fair exchange for his upbringing.
Ghaul first came to Calus's attention as a new fighter in his coliseum. His striking sun-bleached white skin, combined with his singular skill and measured, patient approach to combat, quickly made him the Emperor's favorite Gladiator. Calus would amuse himself by forcing those who had displeased him to bet against Ghaul, while he bet for him. However, Calus began to grow apprehensive of wasting Ghaul's skill in the coliseum, and so elevated him to Primus of the Red Legion, where he became known as the "Ghost Primus." As the Primus of the Red Legion, Ghaul quickly became indispensable to the Emperor not only for his skill in battle but also his wisdom. Ghaul soon found himself as the right hand of Calus, who would often discuss his plans and ideas with Ghaul to refine them and temper the Emperor's passion with discipline. Ghaul grew close with the Calus as well, confiding in him how he believed the adversity he had faced throughout his life shaped and strengthened him into the warrior he became.
Despite the growing friendship between Ghaul and Calus and the close trust and faith the Emperor favored him with, Ghaul's loyalties remained with the Consul and he utilized his position to began plotting a coup against the Emperor with the aid of what remained of the Praetorate and a number of Calus' closest allies and advisers. Among the allies he gathered were Calus' own daughter Caiatl, Evocate-General Umun'arath, Calus' bodyguard Shayotet, and Freeborn Otzot, who feared losing her status should Calus free all Psions from slavery. Calus grew concerned about Ghaul's activities and dispatched a spy to follow him, although he did not know the true extent of Ghaul's plans.
Ghaul's plans were complicated by the surviving members of the Praetorate, who sought greater control over him and tried to delay his coup for a more advantageous moment. Ghaul ignored their efforts and rejected their attempts to rule over him, and chose his own time and place to remove Calus from power. Alongside the Consul and the Red Legion, Ghaul personally invaded Calus' palace on Torobatl in the middle of a late-night court celebration and arrested him, with the aid of Caiatl and Shayotet ensuring that Calus' was caught off-guard and unable to resist. Under the cover of darkness, the Emperor and his remaining military supporters were marched into The Leviathan, sealed within, and exiled far into space along a pre-programmed course, as he was too popular to openly execute. Ghaul found himself unable to look into Calus' eyes during the coup and exile, although Calus was unsure why and thought it could be due to shame.
With Calus gone, Ghaul titled himself Dominus and declared himself the leader of a new Cabal regime, where there would be no more emperors and where everyone could attain greatness if they worked hard for it. Under his direction, the Cabal militarized and became a conquering, expansionist empire, and the Praetorate regained little of the power it had held before Calus, although the Consul remained Ghaul's advisor. Ghaul eliminated much of the decadence of the Empire in favor of perfecting the Cabal into what he viewed as an ideal war-driven form. Knowing that Calus remained alive and a potential threat to his rule, Ghaul took steps to hide his movements from the exiled Emperor in an effort to keep his plans secret.
Along with his efforts to hide his movements from Calus, Ghaul had also employed the use of Psions to mask his fleets from the Hive in his conquest of their War moons on the fringe of Cabal space to ensure a "buffer" against invasion.
Skyburner's Distress Call
Centuries after taking power in the Cabal Empire, Primus Ta'aun of the Skyburners legion sent a report to the Cabal High Command detailing the destruction of Fleetbase Korus on Phobos at the hands of a Hive fleet led by Oryx, the Taken King. This report reached Ghaul who gave Ta'aun explicit orders to board the Dreadnaught and eliminate Oryx. Following the taking of Ta'aun and the deaths of Valus Mau'ual and Valus Tlu'urn, Cabal forces on the Dreadnaught sent a detailed distress signal to Ghaul. While a Guardian managed to stop the signal, The Dead Orbit found evidence that the signal had reached its intended target.
The Red War
Fall of the Last City
Dead Orbit's assertion was confirmed two years later, when Ghaul led his Red Legion in an invasion of the Last City, instigating the Red War. In attacking the City, Ghaul sought to show the Traveler the error of its ways in choosing humanity over the Cabal and establish a new order of Guardians from within the ranks of his own species.
Ghaul's assault was carried out flawlessly. Taking the City by surprise, the Red Legion rapidly overwhelmed it and destroyed the Tower while his cage device latched onto the Traveler. Ghaul's forces took particular care to capture the Speaker alive, Ghaul being interested in his connection to the Traveler. In a desperate plan to kill him, The Guardian boarded his flagship, the Immortal, and destroyed its shield generator in advance of a concentrated attack. This attack never materialized, and Ghaul personally stepped out to confront the Guardian. As the two faced off, the Cage activated its suppressive shield and stripped the Guardian -- all Guardians -- of their Light. His victory assured, Ghaul beat and mocked the Guardian before kicking them off of the Immortal.
Discussions with the Speaker
Days later, aboard the Immortal, Ghaul implored the Traveler to choose him and join his empire. The Consul, in contrast, only viewed it as an advanced machine, and advised Ghaul to simply seize its Light by force. Ghaul disagreed with the Consul's approach and had the Speaker brought to him.
In addition, he sent his prized warship, The Almighty, to the system's sun to destabilize it and cause it to go supernova should the system resist any further. His remaining forces have been sent to the European Dead Zone to hunt the remaining Guardians, to Io to mine the remaining energy from the Traveler and to Nessus to study the Vex. Ghaul also met with Bracus Zahn to acquire advanced weaponry for the Red Legion. He questioned the rogue arms dealer if he had brought all his weapons, who claimed he would not have made the journey to the Dominus' "throne room" without them. The flippant nature of Zahn prompted a rebuke from the Consul, but Zahn suggested that they not waste the time of their only weapons supplier. Ghaul, the Consul, and the other Legion personnel present were angered by this response, but had no choice but to deal with him.
After days of brutally interrogating the Speaker, Ghaul began to accept that to earn the Traveler's favor he would need to learn devotion and self-sacrifice, but his interrogation of the Speaker was interrupted by a furious Consul. His old advisor informed him of the Guardian's efforts to humiliate the Red Legion's forces across the system using their restored Light, their disablement of the Almighty, and the plan to use the City's remaining forces to launch an attack to liberate the City and the Traveler. With this, the Consul angrily informed Ghaul that they had failed for the first time in the Red Legion's bloody history due to Ghaul's fixation with an "inert machine" and a "creature who claims to speak to it". This angers the Dominus.
The Consul demanded that Ghaul take the Light by force to defeat their enemies but Ghaul remained adamant that he should prove his worth. This led the angered Consul to kill the Speaker. He reminded Ghaul of how he took him in and raised him for greatness, not the Traveler, and how he had risen from a lowly runt to the most powerful warlord in history. The Consul declared that Ghaul dethroned the Emperor Calus and reshaped the Cabal's society, and thus he should take what is his, as the Cabal have always done. Convinced by the Consul's argument but angered by his insubordination, Ghaul throttled his old friend to death and took his warship to the center of the Traveler Cage device to drain the Light by force.
Confrontation with the Guardian
At the top of his warship, Ghaul faces off against the Guardian he defeated before but this time infused with some of the Traveler's Light, having successfully stolen it and becoming a Lightbearer. However, the Light that was bestowed upon him was corrupted. After a fierce battle between the two Light-infused warriors, Ghaul was nonetheless defeated. With his death, Ghaul attempts to use Radiance, and is resurrected as a massive ethereal figure due to his corrupted Light, and he declares himself immortal as he speaks to the Traveler directly. In doing so, the Traveler wakes from its slumber, destroying the device that was harvesting its power and then destroys Ghaul himself, sending a massive shockwave across the planet and system, restoring the Light and ending Ghaul's threat forever. For the first time in history, the Red Legion has known true defeat and the leader of their people, their strongest warrior and Dominus, is now dead.
Legacy
Following Ghaul's death and the liberation of the Last City, the Red Legion maintain a foothold in the Sol System but have become seriously weakened and demoralized at the loss of their leader. Eventually, command of the Red Legion was usurped by Val Ca'uor, who sought to revitalize the legion by acquiring energy and supplies from Mars and Mercury respectively. However, such campaigns lead to further conflicts with the Guardians, the Vex and the Grasp of Nokris Hive faction.
Despite continued setbacks from the Guardians, Val Ca'uor decided to further empower the Red Legion by stealing the massive spaceship, The Leviathan, the personal pleasure-craft of Ghaul's predecessor, Emperor Calus. Ca'uor gathered a large fleet and managed to storm the Spire of Stars to assume control of the vessel. However, Calus called upon the Guardians to repel the Red Legion in exchange for riches and rewards. Like Ghaul, Ca'uor would fail against the Guardians, leading to a crippling defeat for the Red legion and the end of the Red War.
With Ca'uor's death, the Red Legion was leaderless for a time, although its remnants were still active across the system. Eventually, a trio of Psion Flayer sisters would rally these remnants on Mercury, finding and exploiting The Sundial of Osiris in an attempt to alter the timeline and reverse Ghaul's defeat in the Red War. However, the sisters had their own motivations in doing so, desiring to use their knowledge of Ghaul's failures not just to win the Red War, but to puppeteer Ghaul so that they might find freedom for the Psion race from the Cabal. Their failure at the hands of Guardians caused a fourth sister, Amtec, to launch Ghaul's prized weapon, the Almighty, at Earth, though it would be destroyed by Rasputin. In the ensuing power vacuum, Ghaul's fellow co-conspirator and daughter of Calus, Caiatl, the Princess-Imperial, has begun rallying the Red Legion once more, proclaiming that she will surpass Ghaul's weaknesses. As of Season of the Hunt, her emissaries have arrived in the system and begun to interact with the remaining Red Legion troops.
Though Ghaul failed in his goal of claiming the Traveler's Light, his actions in the Red War and nearly destroying the last bastion of humanity would remain a bitter memory for the Guardians and survivors of the initial attack. As a result, Ghaul's form would be used as a Nightmare in the newly emerged Hive fortress on Luna.