The Praetors of Ultramar is one of the ten Astartes Chapters permanently assigned by Lord Commander of the Imperium Guilliman with defending the Realm of Ultramar in the wake of the Plague Wars. The Praetors were created after the end of the Indomitus Crusade in the early 42nd Millennium and their numbers were originally drawn from the remaining Unnumbered Sons of Ultramarines descent. These were the nine Legion-sized forces which comprised half of the Primaris Space Marines created during the Ultima Founding who were not placed within the normal Adeptus Astartes Chapter structure. Their Chapter homeworld was named Howsbridge.
For ten millennia, Archmagos Dominus Belisarius Cawl has been working on a task set for him by the Primarch Roboute Guilliman before he was mortally wounded by the Daemon Primarch Fulgrim in the days after the Horus Heresy: a new legion of transhuman warriors. Developed on orders from Guilliman 100 standard centuries past, Primaris Space Marines were diligently developed and perfected by the Priesthood of Mars during the long intervening millennia. As an optimist, but never a fool, Guilliman learned from the mistakes of the Horus Heresy, and he foresaw that the Forces of Chaos would never relent in their aim to bring the Imperium low. He anticipated that devastating times would once again engulf the galaxy and knew that warriors resilient enough to stand against them would be needed as never before. That time has surely come. Now, as the Imperium of Man is poised on the brink of annihilation at the hands of Chaos, his task is at last complete.
The Primaris Space Marine is a new breed of hero for this, the darkest age in the Imperium's history. These new warriors are the next step in the evolution of the Emperor's Angels of Death -- genetically altered from their brethren to be bigger, stronger and faster -- timely reinforcements for the Imperium's armies as their enemies close in for the kill in the wake of Abaddon the Despoiler's 13th Black Crusade and the birth of the Great Rift dividing the Imperium in two.
To aid them in battle, these gene-forged warriors are equipped with new arms and armour forged on Mars itself, such as the Mark X Tacticus Pattern Power Armour worn by the Primaris Space Marine Intercessors, which combines the most effective elements of ancestral Horus Heresy patterns of battle-plate with more recent developments in Power Armour technology; the Mark II Cawl Pattern Bolter, the archetypal firearm of the Adeptus Astartes, now re-engineered, re-crafted and perfected, and Redemptor Dreadnoughts.
At the dawn of the Indomitus Crusade to retake the Imperium from the advancing armies of Chaos and xenos alike, Lord Commander of the Imperium Roboute Guilliman has gathered his new armada, along with elements of the Adeptus Custodes, a small contingent of the Silent Sisterhood and a vast war host of Primaris Space Marines as he fights to liberate the scattered bastions of the Imperium. Some, such as the Praetors of Ultramar, Guilliman has forged into new Space Marine Chapters, whole brotherhoods comprised only of these new transhuman warriors. Others he has offered to the existing Space Marine Chapters. Many Chapter Masters have welcomed their Primaris brethren into their ranks, accepting the new reinforcements gladly. Others, though, view these new creations with suspicion or outright hostility, claiming that the Emperor's work should never have been meddled with by mere mortals.
Though they are a step removed from their brothers, the Primaris Space Marines still bear the gene-seed of their Primarchs, and some dissenting voices worry how this new type of warrior will react with the known genetic quirks and flaws of some of the more unusual Chapters, such as the Blood Angels and the Space Wolves. Though the Primaris Space Marines offer new hope to a besieged Imperium, the future remains a dark and uncertain place...
- Guardians of Ultramar (Unknown Date.M42) - The Knights Cerulean were originally among the members of the Unforgotten Sons who accompanied Primarch Roboute Guilliman when he went to the aid of the Realm of Ultramar during the Plague Wars. Following the conflict and the formal end of the Indomitus Crusade, Guilliman created the Praetors of Ultramar Chapter from Primaris Space Marines descended from his Ultramarines lineage and charged them with being one of the ten Chapters assigned to the region to permanently defend Ultramar from further attacks by the Forces of Chaos.
The Praetors of Ultramar's Chapter colours are currently unknown in Imperial records.
The Praetors of Ultramar's Chapter badge is not currently listed in Imperial records.
- Dark Imperium (Novel) by Guy Haley, Ch. 20