Torchbearers were the specialised task forces of the Indomitus Crusade whose mission was to give the genetic engineering technology and Adeptus Mechanicus Tech-priests required to create Primaris Space Marines -- known as the "Primarch's Gift" -- to the already extant Firstborn Space Marine Chapters.
Early during the muster of the Indomitus Crusade Fleets, specialised task forces were assembled and sent racing out into the galaxy. Known as "Torchbearers," they were tasked to make contact with specific Firstborn Space Marine Chapters and to furnish them with the "Primarch's Gift" -- the name given to the genetic technologies and Magi Biologis required for those Chapters to create their own Primaris Marine Battle-Brothers.
Torchbearer task forces typically comprised small, fast, heavily armed craft and were garrisoned with a mixture of Sisters of Silence, Adeptus Custodes of the Emissaries Imperatus, and Greyshield Primaris Battle-Brothers of the same genetic line as the chosen Chapter to be reinforced. These escorts ensured that their precious cargo reached its destination regardless of threats and impediments and was put swiftly to use by its recipients.
Some Chapters were assigned Torchbearers because they were known to be nearing -- if not already past the brink of -- extinction. Task forces despatched to these so-called "waning" Chapters had first to locate them and determine if they still fought on in the Emperor's name, then begin the replenishment of their strength if they did.
If tragedy had already overtaken the waning Chapter then a new Chapter Master was selected from amongst the Greyshields and the Chapter was reestablished, their first duty often to exact vengeance upon whatever foe had laid their forebears low.
Many Torchbearer task forces were assigned to those Chapters simply too far distant, or else too mobile in nature, for the main thrust of the Indomitus Crusade Fleets to reach. Many such Chapters had homeworlds that lay beyond the roiling mass of the Great Rift. Others, including such illustrious names as the Ultramarines, the Black Templars, and the Raven Guard, inhabited regions far from Terra or were scattered across the void aboard crusading fleets.
Torchbearers assigned to these Chapters employed every asset that might lend them speed and efficacy. Most boasted multiple cadres of Silent Sisters, their presence intended to quell the most ferocious of Warp Storms and aid their comrades in weathering an often-desperate passage through the madness of the Cicatrix Maledictum.
Some further augmented their ranks with Rogue Traders whose voidcraft and knowledge of hidden routes was invaluable, especially potent Astropaths to aid in making contact with their quarry, and brotherhoods of Grey Knights to stave off the perils of malefic interference with the Torchbearers' vital mission.
Saving the Angels Revenant
For the task force sent to locate the Angels Revenant it appeared at first as though the Chapter was extinct and their duty was to reestablish it in whole. The Chapter's homeworld of Libethra had been cracked open by the Necrons of the Maynarkh Dynasty in order to engulf the original Angels Revenant in lava.
No trace could be found of those scattered Battle-Brothers who had avoided the tragedy. Yet even as Torchbearer forces set down upon the riven, airless carcass of Libethra and prepared to declare the waning Chapter extinct, their auspex and Vox networks picked up faint signs of ferocious battle taking place deep beneath the planet's surface.
Tales are told elsewhere of the subsequent battle for dead Libethra against the Necron menace, of the alliance between the Torchbearers and the last vengeful remnants of the Angels Revenant, and of that Chapter's rebirth amidst the furnace of war -- suffice to say that the Primarch's Gift ushered in a new era for the Angels of Libethra.
Sons of Medusa
Some Torchbearer task forces were assigned to Chapters who, for reasons of doctrine, genetic heritage, or historical circumstance, were expected to resist the bequest of the Primarch's Gift. It was unacceptable, but not unbelievable to Guilliman and his advisors, that the most traditionalist or headstrong Firstborn Chapters might wholly reject the Primaris gene-tech or the intrusive presence of the Adeptus Mechanicus magi who accompanied it.
In such cases the task force's complement of Adeptus Custodes was typically larger than average. Their presence left no doubt that this boon came by the grace of the Emperor Himself and that to resist its implementation was to deny the will of the Master of Mankind. Just such Torchbearer forces were dispatched to locate the tripartite fleet elements of the Sons of Medusa.
Resistance was predicted from their three War Clans: Lachesis, Mageara, and Atropos. The gene-seed used to fashion their Primaris Marine reinforcements came from that of their parent Chapter, the Iron Hands, and the internecine savagery of the Moirae Schism had left no love lost between them and the Sons of Medusa.
In the event, the task force sent to locate the Lachesis War Clan had the easiest duty; by the time they had rushed to aid the Sons of Medusa in their battle against the Orks of the Dravus Cluster and fought alongside them for a full Terran year the martial bonds they forged superseded all other barriers.
Those Torchbearers assigned to the Mageara and Atropos fleets, however, faced much greater challenges that went far beyond resistance from the Sons of Medusa themselves.
- White Dwarf 39 (November 2019), "Dawn of the Era Indomitus," pp. 46-51