The Unnumbered Sons, officially known as the Unnumbered Sons of the Primarchs, and unofficially among themselves as the "Greyshields", were nine special formations of Primaris Space Marines created by Lord Commander of the Imperium Roboute Guilliman for service in the Indomitus Crusade. Active for over a standard century well into the 42nd Millennium, they were comprised of nine Space Marine Legion-sized armies of Primaris Space Marines, all drawn from the lineage of one of the 9 Primarchs who had led the Loyalist Space Marine Legions during the Horus Heresy.
Approximately half of the Primaris Space Marines created during the Ultima Founding were formed into entirely new Chapters of the Adeptus Astartes, while the remaining half were placed within the Legion-sized armies of the Unnumbered Sons. However, unlike the new Chapters, Guilliman forced these armies to fight using mixed squads that contained Primaris Astartes from multiple different gene-lines to better forge cooperation between the different lineages.
The Unnumbered Sons served as a reserve force for Guilliman during the Indomitus Crusade, their ranks slowly reduced by attrition and the need to replenish already-extant Chapters of the Adeptus Astartes with the new class of Primaris Space Marines. Other members of the Unnumbered Sons were eventually integrated into whole new Chapters comprised only of Primaris Astartes like their brethren.
By the end of the Indomitus Crusade at the Battle of Raukos, over a standard century into the 42nd Millennium according to the original Imperial Calendar, the armies of the Unnumbered Sons had been reduced to approximately 20,000 Primaris Astartes. These were ultimately disbanded and divided up into a final group of new Primaris Chapters on the orders of Guilliman before he began his intervention in the Plague Wars of Ultramar.
Archmagos Dominus Belisarius Cawl had created hundreds of thousands of Primaris Space Marines beneath his forge 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 in 999.M41, the Primarch directed Cawl to divide half of the newly-awoken Primaris Space Marines of the Ultima Founding into new Chapters of Adeptus Astartes. Each of these Chapters were composed of Primaris Astartes wholly descended from a single one of the nine original Loyalist gene-lines. The other half of the Primaris Astartes 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 Astartes belonging to all nine of the Loyalist Primarchs' gene-lines. Each of these Primaris Astartes wore the livery of his progenitor Primarch, and each Unnumbered Sons Legion was further divided into Chapter-size units of 1,000 Primaris Marines. These units were further divided into companies and squads, each of which was a mixed formation.
Guilliman had ordered the Unnumbered Sons to fight as mixed gene-line units in the hope that the Primaris Astartes 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 prevent the eruption of 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 into the second century of the 42nd Millennium, 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 standard 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 Prime 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 standard counterparts.
By the time of the Battle of Raukos at the very end 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 brought the Indomitus Crusade to its end and disbanded the remaining Greyshield armies as he moved to intervene in the Plague Wars of Ultramar. 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.
Unnumbered Sons Badge
All Unnumbered Sons were marked with the same badge on their shoulder pauldrons regardless of their gene-line descent -- pale grey chevrons. This badge set them apart from the other Primaris Space Marines who were either placed from the start within new Chapters or were later assigned as replacements for already extant but badly depleted Chapters of the original Astartes during the course of the Indomitus Crusade. This badge was the source of the Unnumbered Sons unofficial moniker, the "Greyshields."
Notable Unnumbered Sons
- Aldred - Aldred was an Inceptor from the genetic line of Rogal Dorn and the Imperial Fists. He served in the same squad as Justinian Parris.
- Sergeant Bjarni Arvisson - Arvisson was a Sergeant of an Inceptor Squad from the genetic line of Leman Russ and the Space Wolves. After the disbanding of the Unnumbered Sons, he became a founding member of the Wolfspear Chapter.
- Quentus Carmagon - Quentus Carmagon was an officer of the Unnumbered Sons of the genetic line of Roboute Guilliman and the Ultramarines. He later became the Captain of the Knights Cerulean Chapter 3rd Company after the Unnumbered Sons were disbanded.
- Ciceron - Ciceron was a member of the Unnumbered Sons from the genetic line of Roboute Guilliman and the Ultramarines.
- Cordus - Cordus was an Inceptor from the genetic line of Roboute Guilliman and the Ultramarines. He served in the same squad as Justinian parris. He was killed in action during the Battle of Raukos.
- Decimus Felix - A former Inceptor Lieutenant of the Unnumbered Sons, Decimus Felix was a scion of the genetic line of Roboute Guilliman and the Ultramarines. He later became Guilliman's Equerry during the Indomitus Crusade and was also made the Eleventh Captain of the Ultramarines Chapter at that time, the first alteration of the Ultramarines' Codex Astartes-dictated order of battle in over ten thousand standard years. Decimus Felix was later named by Guilliman as one of Ultramar's new ruling class of Tetrarchs, an ancient rank that the Primarch had decided to restore to prominence. Felix was given rulership over the Ultramaran world of Vespastor, and charged with enlarging Ultramar's eastern expanse by whatever means necessary.
- Lei Jian - Lei Jian was a member of the Unnumbered Sons descended from the genetic line of Jaghatai Khan and the White Scars.
- Kalael - Kalael was an Inceptor of the genetic line of Lion El'Jonson and the Dark Angels.
- Sergeant Justinian Parris - Parris was an Inceptor Squad Sergeant from the genetic line of Roboute Guilliman and the Ultramarines who served in the company under the command of Lieutenant Sarkis. He later joined the Novamarines Chapter as part of its new Primaris Space Marine contingent and took part in the Plague Wars.
- Sergeant Rusticus - Rusticus was the Sergeant of an Inceptor Squad in the Unnumbered Sons.
- Lieutenant Sarkis - Sarkis was an Inceptor Primaris Astartes from the genetic line of Ferrus Manus and the Iron Hands.
- Solus - Solus was an Inceptor in Sergeant Rusticus' squad and was a scion of the genetic line of Sanguinius and the Blood Angels.
- Urstan - Urstan was a member of the Unnumbered Sons of the genetic line of Rogal Dorn and the Imperial Fists.
- Dark Imperium (Novel) by Guy Haley, Chs. 7, 13, 15, 20