|Heraldry is identical to each member's primogenitor Chapter.|
|Battle Cry||Unknown, likely nonexistent|
|Successors of||All First Founding Chapters, possibly ALL First Founding Legions|
|Successor Chapters||Multiple Ultima Founding Chapters (those formed during and immediately after the Indomitus Crusade) as well as some refounded Chapters (de facto anyway)|
|Chapter Master||n/a, under direct command of Guilliman|
|Primarch||All the Loyalist Primarchs (and maybe the others too although nobody can prove that)|
|Homeworld||Mars (Effectively, No homeworld was ever established)|
|Strength||About 20,000 at the time of the Indomitus Crusade's end, currently disbanded into the Ultima Founding Chapters and into other Chapters in need of reinforcements, formally defunct.|
|Specialty||Great coordination and cooperation between astartes with different gene-seed, being a massive pool of reinforcements during the Indomitus Crusade.|
|Colours||Pale Grey, with heraldry of each member's primogenitor displayed on their pauldrons|
The Unnumbered Sons (full name being the Unnumbered Sons of the Primarchs, colloquially known as the Greyshields) are a Chapter of Astartes formed during Ultima Founding, during the Indomitus Crusade. Created by the Lord Commander of the Imperium Roboute Guilliman, this Chapter was comprised of only Primaris Marines, numbering around nine times legion-size. This unnatural size for a chapter is due to the fact that the Unnumbered Sons originally included the entirety of the existent Primarines, made with the geneseed of the nine loyalist primarchs, and made to work as a unit to improve the synergy between different chapters.
Origins of the Unnumbered Sons
After Archmagos Dominus Belisarius Cawl unveiled his 10,000 year project to Guilliman, the Imperium had thousands of these new Primaris Marines ready and available for use. The beginning of the Indomitus Crusade and the Ultima Founding meant that this massive force would have to be used on the battlefield as soon as possible. Thus, the Unnumbered Sons, famous for not wearing any chapter heraldry (having nothing drawn on their pauldrons and nor any colour on their armor, hence the nickname "greyshields"), were forced to push the tides of Chaos back and stop the 13th Black Crusade. During the duration of the conflict, Guilliman used this chapter to draw reinforcements and new chapters, reinforcing under-strength chapters with new blood and establishing entire primarine chapters. This, combined with the losses caused by attrition, meant that the Greyshields' numbers began to shrink fast.
By the time Roboute Guilliman declared the end of the first phase of the crusade, around 20,000 Greyshields still existed. After the Battle of Raukos was over, Guilliman (having declared the Indomitus Crusade over and his intent to fight Mortarion in the Plague Wars) ordered the disbandment of the Unnumbered Sons, to either add them to already existing chapters who had yet to receive reinforcements or to create more new Astartes Chapters from the final core of veterans to cap off the Ultima Founding; formally rendering them defunct.
The Bond of Countless Brothers
Though they may now be disbanded, at their peak, the Greyshields (yes, the real name is technically the Unnumbered Sons but Greyshields sounds way cooler) were one of the greatest united forces of Space Marines in the Imperium's history. The sheer diversity between even a single squad of Greyshields guaranteed a slew of varying tactics within the group's arsenal. Sons of Russ charged headlong into the fray, chainswords roaring, alongside the children of Dorn, covering their advance with the explosive symphonies of heavy bolters. White Scars dove into combat atop attack bikes while Dark Angels melted their queries with searing hot plasma. A few Greyshields fighting together is massive Fa/tg/uy porn. A whole detachment? Prepare the holy lube. This brings up the question of why didn't Guilliman just allow new Primaris chapters to use multiple geneseed sources instead of a single type, since they seemed to cooperate well enough as brothers without their origins becoming any impediment.
The Greyshields notably fought all through the Indomitus Crusade, all the while dwindling in number, as Guilliman passed planets on his righteous tour of the galaxy shouting "YOU get a Primaris chapter, and YOU get a Primaris chapter!" until the Unnumbered Sons were reduced to merely TWO LEGIONS WORTH (albeit two small legions, see the First Founding article for the full numbers), when they fought one last time as one big brotherhood at the Battle at Raukos. After that Bobby G had 'em all disperse at once, breaking the bonds the Primaris Marines had forged over roughly a century. So, with mixed feelings, the Greyshields took up the armor of their new chapters, some returning to their Primarch's chapter, some forming new ones, and some going to the few existing chapters that hadn't yet received reinforcements.