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Sali 'Nyon is a Sangheili Zealot who previously was in the service of the Covenant faction under Supreme Commander Jul 'Mdama, but after the events on Requiem, he launched a failed attempt to rebel against Jul 'Mdama.
Battle of Aktis IV
After the events on Requiem and Jul 'Mdama allied himself with Doctor Catherine Halsey, Sali began questioning 'Mdama's true intentions. Sali started to recruit his own followers, viewing himself as the true Hand of the Didact, and plotted against Jul. By July 2558, amidst the Battle of Aktis IV, his followers were identified by 'Mdama's forces. During the battle, after 'Mdama's forces tricked the UNSC into delivering their half of the Janus Key to Aktis IV's surface, 'Nyon's followers shot down the D79-TC Pelican carrying the Key. This led to confusion among 'Mdama's ranks, whom recognized the attack to be unauthorized by 'Mdama. Nonetheless, 'Mdama's fleet proceeded with their planned attack on the orbiting UNSC Infinity ahead of schedule. Meanwhile, 'Nyon made his way to the Pelican's crash site and retrieved the UNSC's half of the Janus Key for himself.
Traveling to the surface of Aktis IV himself, 'Mdama and his forces began to eliminate 'Nyon's insurgents. 'Nyon broadcasted a message across Jul's entire fleet to incite them to join him in rebellion. 'Nyon, with his half of the Janus Key, retreated to his hideout in a jungle. A Sangheili Zealot approached him about the feasibility of continuing the rebellion, to which 'Nyon responded by reassuring his followers that the Forerunners had blessed them, citing his recovery of half of the Janus Key as proof. A Sangheili Minor stated that the Prometheans' allegiance to Jul 'Mdama was evidence to the contrary, but 'Nyon insisted that the answers to their questions would all be revealed in time. While 'Nyon left to help aid the wounded, the Minor, disillusioned with 'Nyon's rebellion, stole his half of the Janus Key and departed on a Type-32 Ghost. The Minor contacted a Zealot serving under 'Mdama, and promised to provide the stolen Janus Key half and 'Nyon's location of his hideout. The Zealot reluctantly agreed and prepared to establish a rendezvous point.
Not much later, 'Mdama's forces would discover 'Nyon's hideout. Most, if not all, of his followers were killed, and 'Nyon himself was imprisoned. His rebellion had effectively came to an end. 'Mdama, however, would decide to keep 'Nyon alive for the time being.
The Absolute Record
For the next two months, Jul kept 'Nyon incarcerated in a holding cell aboard his personal's flagship, Song of Retribution. Two days prior to setting a course for the Absolute Record, 'Mdama visited Sali 'Nyon in his cell for further interrogation. 'Nyon criticized 'Mdama for his nontraditional method of keeping a prisoner, and he refused to divulge the number of traitors within 'Mdama's faction.
Until September 17th, 2558, Sali was kept by Jul aboard the Song of Retribution as he journeyed to a planet that would lead to the Absolute Record. With the fleet damaged by slipspace ruptures, Jul decided to transfer Sali to the damaged Breath of Annihilation, setting down for repairs on a nearby moon, while he took the Song of Retribution alone through the portal. Needing a distraction to keep Spartan Gabriel Thorne alive, ONI agent Ayit 'Sevi arranged for Sali's escape, convincing the former leader that he could rally those loyal to him. 'Nyon would lead a revolt aboard the ship, killing those loyal to 'Mdama and seizing control of 'Mdama's collection of Forerunner artifacts taken from Requiem, using them to further cement his support. 'Nyon took the Breath of Annihilation back into Sangheili space to rally further support among the Covenant remnants, not noticing 'Sevi's absence, and was shortly after engaged by the Song of Retribution, a battle that ended in stalemate with 'Mdama unable to retake the ship.
After the death of 'Mdama on Kamchatka, 'Nyon emerged as the clear frontrunner for leader of the Covenant remnants, with some Sangheili, even one in the Swords of Sanghelios, viewing him as a true leader compared to the Arbiter and Jul, and the next best chance for a new Covenant.
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