Emperor Calus appointed a younger Ghaul to Primus of the Red Legion, where his talents would be best put to use. For his albinism, Ghaul became known as the Ghost Primus. Under his command, the Red Legion became loyal to Ghaul over their emperor, such that when Ghaul launched his coup against Emperor Calus, the Red Legion accompanied him, arresting Calus and forcing him aboard The Leviathan.
The Legion was last deployed in response to the Skyburners' distress call to attack the Last City on Earth, launching a successful invasion of Earth and the Last City. Using the Traveler Cage, they managed to cripple the Last City and devastate the Guardians, leaving them vulnerable and displaced. They are attempting to claim the Light from the Traveler and become Guardians. Following the attack, the Red Legion began to quickly occupy the Solar System, even making an attempt to dig up ancient Vex ruins on Nessus, where they unearthed the ancient Vex mind Protheon, Modular Mind. Soldiers of the Legion utilize highly advanced technology, far more advanced than that of their older scouts.
Ghaul's death and the Legion's defeat at the City did not substantially hinder their war machine. With the Dominus's command succeeded by Val Ca'uor, the Red Legion began to actively occupy Mercury and Mars in order to resupply their forces. Red Legion forces headed by Kargen, the Technocrat hacked the Insight Terminus on Nessus for Vex technology while Psions were also attempting to evolve into Flayers by tapping into the Warmind Rasputin on Mars; both efforts were thwarted by the Guardians. Around the time the Hive began emerging from the Hellas Basin on Mars, Val Ca'uor led a Red Legion fleet against the Leviathan in order to seize it from Calus and weaponize it. Ca'uor's forces were repelled by The Guardian and was assassinated afterward, thus leaving the Red Legion leaderless again, weakened and further demoralized.
In addition to their disheveled state, the Red Legion began suffering from multiple desertions such as those following Garut Gra'am who rooted themselves in Trappers Cave. The most prominent of these groups, the Unbowed Legion, made their debut in the EAZ during the Solstice of Heroes event in an attempt to take over the EAZ as a base of operations. Despite the group being lead by three large Cabal commanders similar to Ghalak the Colossus, Forge Warden, they were quickly put to an end by the Guardians partaking in the event.
More recently a family group of Psion Flayers, having commandeered Osiris' time-traveling Sundial, split Mercury into three alternate timelines that threaten to span beyond the planet and into the system. It is their intention to undo Ghaul's defeat, or, failing that, gathe enough Light from the future to buy their way back into Calus' favor. Though the Psion Flayer sisters, Niruul, the Hollow Voice, Ozletc, the Sky Piercer and Tazaroc, the Sun Eater, managed to create a border realm for themselves, the Guardians would ruin their plans. One by one, the Psion sisters would face the Guardians and be defeated. After weeks of their forces being eliminated, the three sisters, driven to desperation, used their vast psionic powers to merge into a single being, Inotam, Oblivion's Triune. Despite Inotam's vast powers, the Guardians would nonetheless prevail against her, thwarting the sisters efforts to subvert time. However, one sister remains, Amtec, who was informed by her sisters of their possible demise and now schemes to avenge them.
After their crippling defeat at the Sundial, the Red Legion, headed by the escaped Psion Flayer, Amtec, decide to use the Almighty to crash into the Last City itself. With little to no choice, the Vanguard decide to cooperate with the Warmind Rasputin, with Guardians arming his arsenal, in order to save their home from destruction.
Named Leaders and Bosses
The command structure and tactics of the Red Legion are more aggressive and agile than any Cabal Legion observed before, with deadlier weapons, advanced technology, and battle techniques. The Red Legion also has a handful of new units that operate in the field. Majors will typically wear silver armor, whereas Ultras wear gold armor.
Red Legion troops can be primarily identified by their signature gunmetal and red color scheme, with some troops having gold, silver, or orange highlights depending upon their rank. They are also more heavily armored than other Cabal Legions, wearing metal plates over a bodysuit of War Beast scales. 
List of appearances