‘Brothers, we are approaching the insertion point,’ voxed Lieutenant Sarkis. ‘Drop in two minutes. Begin final preparations. Imperator victoriam!’

‘Victoriam!’ his warriors replied.

Of the many tens of thousands of Primaris Space Marines created by Belisarius Cawl, only half were initially formed into new Chapters. The rest had been gathered into great armies, each of one gene-line. They wore the livery of their founding primarchs, their badges crossed with pale grey chevrons, and within their gene-groupings they were then further organised into Chapter-sized formations.

There, agreement with the Codex Astartes ended.

Guilliman deployed his new weapons in every way imaginable. The Primaris Space Marines sometimes fought as the Legions of old had, in huge formations of one type, but they also fought in mixed groups of every size, from strike teams of five up to double Chapter strength. They knew the strengths of their gene-cousins, and their preferences. Brotherhood crossed the lines of primarch and gene-seed. Officially, they were designated the Unnumbered Sons of the Primarchs, but they called themselves the Greyshields. They were the new sons of old science, and they had no fraternity but their own.

As the Indomitus Crusade progressed, the Unnumbered Sons had dwindled. Roboute Guilliman took them from their companies and their squads, and he assigned them to understrength Space Marines Chapters encountered on the way. Whole companies might be hived off, or only a few units. Sometimes the primarch took them by the hundred to create new Chapters where he saw the need: to guard important worlds, or to scour an area of space, or to perform whatever other task he deemed important. Warrior by warrior, the Unnumbered Sons were scattered across the galaxy, taking with them the secrets of their creation to their new homes. Sons of Guilliman became Aurora Marines or Doom Eagles; sons of Dorn joined the Black Templars or the Imperial Fists; sons of Corax became Raven Guard or Revilers. By the time the fleet reached Raukos, only twenty thousand of the Unnumbered Sons’ original strength remained in the Indomitus Crusade.

For one such mixed brotherhood, the final battle approached.

Sergeant Justinian and his Inceptor squad hung from robotic drop arms. There were three warriors in each unit and six units in their bay, along with their leader, Lieutenant Sarkis. Cordus, scion of the line of Guilliman, flew with Justinian, as did Aldred of Dorn’s breed. In the ship’s other two drop bays, thirty-six more Primaris Space Marines awaited battle. They were giants clad in drop armour – Inceptor battleplate reinforced for solo atmospheric re-entry – and equipped with heavy jump packs for sustained flight. For armament, they carried paired assault bolters. Like their armour, these guns were one of Belisarius Cawl’s heretical marvels, massive pistols with the stopping power of heavy bolters.