Editing Imperium Asunder Campaigns (section)

===12th===

In the Grey Stars near the western border of Imperium Minorum, an upstart race called the Tau suddenly begins expanding and claiming territory across the stars. Expanding out from their homeworlds of Tau and Tau'n, the xenos begin to encroach upon imperial settlements. Colonial PDFs prove ineffective at holding back the highly advanced technology of the Tau, and many human lives are lost in the name of the Tau's greater good.

In the Imperial Senate on the throne world of Terra Nova, Alexios the White and his angels petition for a united crusade against the xenos upstarts. Anders Kor, who had held himself aloof from the Senate since its founding, came to speak for the Tau. The Primarchs debated the Tau question for many months, Alexios presenting his arguments clearly, and Anders retorting with confident rebuttals. Alexios spoke of many practical concerns, of duty, honor, and the unity of the human race under the God Emperor of Mankind. Anders spoke of morality, of the wrongness of exterminating a species.

As the primarchs debated in the senate, war against the Tau raged on Imperium Minorum's borders. New chapters of Angels were founded, and the Varangiran Guard began entrenching the border worlds. In the border system of Kythera, the Gryphonwing Chapter uncovered the involvement of Blackshield Paladins supporting the Tau military. The Blackshields and their Tau puppets are defeated at Kythera, and word of the Paladins' involvement soon reaches the ears of the Senate.

Due to the destructive nature of the battle that took place on Terra Nova after Alexios' death, records are unclear as to how or why exactly he was killed. in Imperium Minorum it is said that Anders struck down the White Angel when his treachery was revealed. In most of the crusader states, it is said Anders knew nothing of the treachery of one of his rogue elements, and when Alexios called him a traitor to his face, he lashed out in anger. In some more conspiratorial corners of the galaxy, it is whispered that Alexios threw himself onto Anders' blade, knowing that his death would ignite a war. In the Protectorate of Kor, to even speak of the incident is to incur the wrath of Anders Kor, for regardless of reason, Anders' grief is beyond doubt.

The Angel of Light cohorts who came as Alexios' retinue fell into incomprehensible fury when news of the White Angel's death reached their ears. The first shots were fired by the honor guards outside the senate chamber itself. 19 days of open warfare between the Angels and the Paladins took place on Terra Nova before the Custodes could put a stop to it. The Astartes returned to their crusader states, and as soon as fighting on Terra Nova ended, fighting across the galaxy began.

The war between the Angels and the Paladins was bloody, gruesome, and costly. Black Paladins and the Tau were pushed back quickly by the rapid assaults of the Angels, but war on the eastern front against the Protectorate did not go as easily. Prolonged naval battles with many losses strained the industrial capacity of both crusader states, and the high lethality of combats strained the recruitment resources of the Astartes and guardsmen alike. Eventually the war becomes far too costly for both sides, and a peace accord is called on Terra Nova by the ruling council of the Jade Empire. The Sky Serpents pressure the two sides into peace by threatening to join the conflict themselves. The terms are twofold: a neutral demilitarized zone is established between the Protectorate and the Angels of Light, and the Tau are exterminated. The homeworlds of Tau and Tau'n are given the Rite of Exterminatus, the surviving Tau are exterminated with callous efficiency, and the Mechanicus claims what it can of the Earth Caste's technology. A small enclave of Tau lead by Shas'O Vior'la Shovah Kais Mont'yr survives in a nomadic flotilla, a people without a home.