Unnumbered Sons - History: Archmagos Dominus Belisarius Cawl had created hundreds of thousands of Primaris Space Marines beneath his forge city on Mars during the 10,000 standard years he spent on the project at the direction of the Primarch Roboute Guilliman.When that massive undertaking finally came to fruition after the resurrection of Guilliman and his return to the position of lord commander of the Imperium and Imperial Regent in ca. 999.M41, the primarch directed Cawl to divide half of the newly-awoken Primaris Marines of the Ultima Founding into new Chapters of Adeptus Astartes.Each of these Chapters were composed of Primaris Marines wholly descended from a single one of the nine original Loyalist primarchs' gene-lines. The other half of the Primaris Marines created by the Ultima Founding were divided up into nine armies the size of the massive Space Marine Legions of the Horus Heresy era.Unlike those Legions, however, these formations were created from a mixture of Primaris Marines belonging to all nine of the Loyalist gene-lines. Each of these Primaris Marines wore the livery of his progenitor primarch's First Founding Chapter, and each Unnumbered Sons Legion was further divided into Chapter-size units of 1,000 Primaris Marines. These units were further divvied up into companies and squads, each of which was a mixed formation made up of all the different gene-lines.Guilliman had ordered the Unnumbered Sons to fight as mixed gene-line units in the hope that the Primaris Marines would learn how to deal with the differing temperaments and personalities of their brethren from the other Loyalist lineages in a way that had eluded their ancient predecessors. The lord commander believed this might help prevent the eruption of the inter-Chapter disputes that had so plagued the Adeptus Astartes even after the great betrayals of the Horus Heresy.The Unnumbered Sons proved to be a potent force during the course of Guilliman's Indomitus Crusade to retake the Imperium of Man from the ascendant forces of Chaos and the myriad xenos assaults that threatened to consume it.However, as the crusade wore on, their numbers began to dwindle, both as a result of battlefield attrition and because large numbers of the force were increasingly detached to other duties on the orders of Guilliman.Whenever the crusade encountered embattled Chapters of Firstborn Astartes, the lord commander ordered members of the Unnumbered Sons of the same gene-lines to become replacements for the depleted Chapter's losses. As such, members of the Unnumbered Sons who were scions of Guilliman himself could become new Aurora Chapter Primaris Marines, or Doom Eagles Primaris Marines, or even replacement battle-brothers for the Ultramarines themselves. Primaris Space Marine scions of Rogal Dorn became new members of the Black Templars, the Imperial Fists, and so on for each original Loyalist Astartes lineage encountered as the Indomitus Crusade pushed outwards from Terra.At other times, Guilliman simply created a whole new Chapter of Primaris Space Marines from the Unnumbered Sons' formations to meet a given need such as the defence of a strategically important Imperial world. However, these new Chapters were not mixed and composed of only a single primarch's lineage like their Firstborn counterparts.By the time of the Battle of Raukos at the end of the first major phase of the Indomitus Crusade, only 20,000 Primaris Astartes remained within the depleted ranks of the Unnumbered Sons. The fight to defeat the Chaos forces emanating from the ancient Warp rift in Wilderness Space known as the Pit of Raukos proved to be the last campaign of the Unnumbered Sons, for at its successful conclusion, Guilliman disbanded the remaining Greyshield armies as he moved to intervene in the Plague Wars of Ultramar.Guilliman believed he was forced to disband the Unnumbered Sons by political necessity; there had been rumblings from his opponents in the Terran court that Guilliman was a hypocrite for engaging in "Legion-building" -- the raising of new Space Marine Legions that he had forbidden in his own Codex Astartes. Guilliman had no intention of allowing such charges to serve as an excuse to weaken his authority over the High Lords of Terra or the Imperial nobility, and so with the Imperium Sanctus stabilised following the Battle of Raukos he had felt the time had come to disband the Unnumbered Sons and show that the organisation of the Adeptus Astartes into individual Chapters was still the preferred structure for the Space Marines.Some were formed into new Primaris Space Marine Chapters such as the Knights Cerulean, the Praetors of Ultramar and the Wolfspear, which was tasked with defending the Pit of Raukos.The remaining Unnumbered Sons were dispersed to already established Space Marine Chapters, where they would take the lessons they had learned fighting alongside Astartes of different lineages into units descended only from their own primarchs.