Blooding Years

The Sangheili civil war was a major conflict fought between the forces loyal to Arbiter Thel 'Vadam and the Servants of the Abiding Truth in 2553 on Sanghelios.

Causes
Some months after the dissolution of the Covenant, an ancient religious order of Sangheili known as the Servants of the Abiding Truth continued to preach the divinity of the Forerunners, claiming that while the Covenant's Prophets had been false, the Forerunners were still gods and demanded reverence and respect. Consequently, they felt that Thel Vadam and those loyal to him were committing blasphemy by saying otherwise.

Assault on Vadam
In March 2553, an attempted Jiralhanae insurrection in Ontom led Avu Med 'Telcam, leader of the Servants of Abiding Truth, to the decision for an immediate assault on the state of Vadam. Along with nine ships and forces from Nuan keep and Rtova keep, 'Telcam commanded the assault from the frigate Unflinching Resolve. Eventually, however, the Unflinching Resolve suffered a direct hit and crash landed. Despite being caught off-guard it appeared as though the Arbiter would be victorious, however, news spread that he allowed humans to land on Sanghelios; this caused many keeps to ally with the Servants of Abiding Truth and the tide turned in their favor. The Arbiter was caught off guard and when his own reinforcements couldn't arrive on time, he reluctantly accepted Admiral Terrence Hood's offer for help in fending off the attackers. The tide turned when arrived over Sanghelios and destroyed the rebel destroyer Defender of Faith before finishing off the rebel ground forces with a MAC round. The, posed as a Kig-Yar pirate ship, destroyed a few of 'Vadam's ships in order to maintain the stalemate between the two factions, leaving the Arbiter with a Pyrrhic victory.

After the battle, Thel 'Vadam was in talks to visit the UNSC Infinity, a ship more powerful than any during the Human-Covenant War. The remnants of the Servants of Abiding Truth escaped to New Llanelli to regroup. One month later 'Telcam said he would remain on New Llanelli until he convinced more keeps to join his cause or get enough ships to destroy those who refuse.

Massacre at Nes'alun keep
The conflicts in Vadam led to other engagements throughout Sanghelios. Unlike the majority of keeps in Acroli, Nes'alun keep was against the Arbiter. While the keep's males left to fight Vadam's forces, the keep females and children were left behind. The elder of Lacalu keep took advantage of this and attempted to seize the keep and its land. The keep's lady, Elar 'Nas, defended the other females and children in a small farmhouse for an unknown length of time. Soon the keep's Unggoy laborers Dengo and Gikak returned along with Evan Phillips, who had been teleported to the nearby Forerunner ruins. Elar allowed Phillips to come inside, armed him, and prepared themselves for another wave of attackers. Soon afterwards Kilo-Five arrived at the keep to retrieve Phillips. Their extraction was stalled when the Tart-Cart, piloted by Lian Devereaux, was attacked by several Type-26 Banshees. After holding off more Lacalu warriors, Vasily Beloi, Malcolm Geffen, and Naomi-010 extracted Phillips in the midst of battle, leaving the women and children to defend for themselves. Elar and her clan were later killed which unsettled Phillips.

List of appearances

 * Halo: The Thursday War
 * Halo: Mortal Dictata