A Primaris Marine is a new breed of transhuman warrior of the Space Marines, developed across ten thousand years of secret labour by the Primarch Roboute Guilliman and the geneticist Belisarius Cawl. Larger, stronger, and more resilient than their forebears, the Primaris were created through the addition of new gene-seed organs, refining the ancient template first laid down by the Emperor.
Awakened in vast numbers to reinforce the Imperium during its darkest hour, the Primaris marched to war alongside the older Astartes as the galaxy was torn asunder by the Great Rift. Their arrival brought both salvation and unease, for some among the traditionalist Chapters viewed these new brothers with suspicion, wondering whether they were true Space Marines or something altogether other.
Equipped with advanced Mark X armour and weaponry recovered from ancient archives, the Primaris represent both a continuation and a reinvention of the Emperor's original vision, a testament to how far the Imperium will go to hold back the encroaching dark.