A number of years before his arrival in the Solar System, Calus led a revolt against the ruling Praetorate, a “corrupt military elite,” and became Emperor of the Cabal. During his reign, the Cabal moved away from martial power and towards decadence and festivities.1 Emperor Calus also brought a number of alien species, such as the Clipse, into the Empire.2 When the Psion Otzot rebuilt the OXA machine, Calus did not have her killed; instead, he had her named Imperial Dreamer.1
At some point, Ghaul was sent to Calus’ coliseum. Calus took an interest in Ghaul due to his ability to handle opponents much more powerful than he was. Due to his talent, Calus appointed him Primus of the Red Legion.3 According to Calus, Ghaul was like a son to him.4
Ghaul began conspiring with several of Calus’ associates to overthrow him.5 Other members of the conspiracy included Lictor Shayotet, Calus’ bodyguard; Otzot; Aedile Moli Imoli, the Celebrant; Evocate-General Umun'arath; Iska'al of Fantor, Calus’ confidante; Princess-Imperial Caiatl, Calus’ daughter; and the Consul.1
Ghaul led the coup against Calus under cover of darkness. Calus was sent into exile with a number of his supporters, sealed in the Leviathan and sent into deep space.4
While in exile, Calus was in a stupor for some time. However, he was awoken from this daze when the ship’s navigation system failed, reaching a space that didn’t exist. Calus stared into the void that the ship had reached and saw something looking back; according to Calus, the void then chose him to be the “herald of its victory.”6
After his experience with the void, Calus began exploring the cosmos, discovering ancient worlds and oddities.1 He also began recruiting his Shadows, who were powerful warriors from several alien species.7 Calus then sent his Shadows on a mission to assassinate Ghaul.8 However, the Shadows failed in their mission and were killed.9
After the death of Ghaul, Calus began using the Leviathan to devour Nessus. He also began inviting Red Legion troops to join the Loyalists.10
Following this, Calus invited the Guardian to the Leviathan, where he was seemingly defeated. However, Calus was not killed. Following this event, Calus called the Guardians back to the Leviathan a number of times, first to defeat Argos, Planetary Core, and then to repel Val Ca'uor’s invasion of the Leviathan.
Later, Calus nominated the Guardian to become a Shadow of Calus.11
Around this time, Calus attempted to take control of a Hive artifact, the Crown of Sorrow. He then created the Hive Gahlran, whom he wanted to wear the Crown and control the Hive.12 However, wearing the Crown caused Gahlran to be driven mad.13 Gahlran was also being controlled by Savathûn.1415 The Crown was a trap laid by Savathûn, who sought to control Calus with it.12
After Gahlran’s defeat, Calus made the Guardians the Shadows of Earth.16 He also tried to invite Toland, the Shattered and Eris Morn to be the Shadows of the Hive.17
