This world lies in the Segmentum Pacificus, far to the galactic southwest of the Eye of Terror. As such, it is a rare thing indeed for the Chapter's brethren to appear in the court of Marneus Calgar, and when it does it is a great cause for celebration. Very little was known about Sabatine, due largely to the secretive and defensive nature of the White Consuls.
Not long after the formation of the Great Rift, Sabatine was assaulted by the Heretic Astartes of the Weeping Veil and the Lords of Silence, warbands of the Word Bearers and Death Guard Traitor Legions, respectively. The skeleton force of White Consuls left behind while the majority of the Chapter had been deployed to defend the Imperium from the massive assault that was the 13th Black Crusade proved incapable of protecting Sabatine from the sheer size of the Chaos assault.
Each warband sought to betray the other and seize the world for its own, but the Lords of Silence ultimately prevailed and the Weeping Veil fled Sabatine. Sabatiune has been transformed by the Lords of Silence into a Daemon World that can be considered a facsimile of the Death Guard's own homeworld in the Eye of Terror, the Plague Planet.
The White Consuls, alongside about twenty other Chapters known as the Astartes Praeses, are sworn to protect the Imperium from the depredations of the servants of Chaos -- in particular the Traitor Legions -- who periodically spew forth from the Eye of Terror on one of their devastating Black Crusades.
So that they may prosecute their duty as sentinels of the Eye of Terror whilst maintaining operations against a wide range of enemies of the Imperium, the White Consuls have instigated a highly unusual policy. The Chapter is ruled not by a single Chapter Master, but by two. One of these oversaw the defences of Sabatine and commands a standing force ready at a moment's notice to respond to Chaos incursions through the Cadian Gate, while the other is responsible for the operations of the Chapter's forces in war zones further afield.
This equal division of command works well for the White Consuls, although it is doubtful whether it is sanctioned by any entry in the Codex Astartes. Perhaps the Chapter's great separation from its Progenitor Legion means that it has not been challenged on the matter. In addition to its homeworld of Sabatine, the White Consuls also maintain sovereignty over several nearby star systems which they hold as protectorates, such as the Boros System and its central world of Boros Prime, site of a massive incursion by the Word Bearers Traitor Legion in the late 41st Millennium.
Fall of Sabatine
After the Great Rift opened, the Chaos Gods charged the Weeping Veil Dark Apostle Mor Jalchek with the conquest of Sabatine, the homeworld of the White Consuls Space Marines. The Word Bearers Chapter's flagship, the Styx-class heavy Cruiser Ayamandar, then left the behind the battles of the Cadian Gate raging after the fall of Cadia to carry out the Ruinous Powers' latest sacred task.
However, with the onset of the Noctis Aeterna, the Weeping Veil proved unable to determine Sabatine's exact location in the Warp, no matter what instruments of technology or sorcery they employed. Their difficulties ended when they were approached aboard the Ayamandar by the Death Guard Repulsive-class Grand Cruiser Solace and the warband that commanded it which was known as the Lords of Silence.
The Lords of Silence also desired to conquer Sabatine and their Chaos Lord Vorx explained that he knew its location and promised to lead the Weeping Veil to the White Consuls world if the Word Bearers Chapter agreed to join with them in carrying out the planetary assault. After some consideration, Jalchek agreed to Vorx's proposal, but also secretly planned to betray the servants of Nurgle and allow the Word Bearers' daemonic allies to claim the world for their own once it was conquered.
With their combined forces, the Weeping Veil and the Lords of Silence easily overwhelmed the skeleton garrison force maintained by the Astartes of the 4th Company of the White Consuls, regiments of the Astra Militarum's Praetorian Guard and the world's own Planetary Defence Forces. The servants of Chaos claimed the planet for their own. But when the Weeping Veil moved to betray their allies by sacrificing much of Sabatine's captured population to summon three Greater Daemons and their daemonic legions to the captured world and remove the Nurglites, the Lords of Silence struck first.
Vorx had been prepared for the Weeping Veil's betrayal from the start and he had ordered his warband to poison Sabatine's mortal population with a pathogen prepared by his Biologus Putrifier Slert during the invasion. Before the Word Bearers could initiate their sacrificial ritual, all the people of Sabatine were transformed into Plague Zombies and Poxwalkers who quickly joined with the Lords of Silence to overwhelm the Weeping Veil.
Jalchek was forced to lead his Chapter in a retreat from the world back to the Ayamandar which successfully fled into the Warp. Sabatine was soon transformed into a Daemon World dedicated to the Plague God and became a remarkable facsimile of the Death Guard's Plague Planet within the Eye of Terror.
Luckily for the Imperium, the bulk of the White Consuls Chapter had been off-world when Sabatine was lost, unlike many of their fellow Astartes Chapters in similar circumstances. The effect the loss of their homeworld had upon their unusual Chapter hierarchy remains unknown.
- Codex: Space Marines (5th Edition), pg. 30
- Deathwatch: Rites of Battle (RPG), pg. 56
- The Lords of Silence (Novel) by Chris Wraight, Chs. 10-12, 21-22
- Warhammer 40,000: Rulebook (8th Edition), pg. 51