The Castellans of the Rift is a Loyalist Space Marine Chapter comprised entirely of Primaris Space Marines created from the lineage of the Ultramarines and raised during the Ultima Founding of 999.M41.
The Castellans of the Rift have a dire duty entrusted to them by Roboute Guilliman himself. Despatched to the Nachmund Gauntlet, they are locked in a struggle to drive back the hordes of daemonic war machines and Renegade Knights blighting one of the only stable routes through the Cicatrix Maledictum.
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, 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...
- War of Beasts (Unknown Date.M42) - Since Primarch Roboute Guilliman despatched the Castellans of the Rift to the Nachmund Gauntlet, they have been locked in a struggle to drive back the hordes of daemonic war machines and Renegade Knights blighting that channel of space. When war broke out on the vitally important Imperial world of Vigilus, the greater part of the Chapter was engaged in warfare against the Heretic forces that had revealed themselves on the Knight World of Dharrovar. Still, two companies joined the war on Sangua Terra and a further two travelled to Vigilus. With experience fighting against the machinations of Chaos, in the third stage of the War of Beasts they hunted the dark cults of Storvhal with commendable efficiency and resolve.
The Castellans of the Rift wear pale green Mark X Power Armour. The Aquila or Imperialis on the chest guard is gold. The backpack and right poleyn (knee guard) are black. The shoulder trim is dark green.
Chapter markings and unit designations are white. The white squad specialty symbol is displayed on the right shoulder pauldron, while the left pauldron proudly displays the Chapter's iconography.
The company number is displayed as a Roman numeral on the right poleyn on a field of black. These numerals reflect the Chapter's Ultramarines heritage. The black Roman numeral displayed in the centre of the squad specialty symbol on the right pauldron designates squad number.
Battle-Brothers display pale green helms with a vertical dark green stripe down the centre. Sergeants wear red helms. Veteran Sergeants wear red helms with a white vertical stripe down the centre. Lieutenants wear pale green helms bisected by a large red stripe with a pair of smaller white stripes painted to either side.
The faceplate of the helms is painted white rather than green, mirroring the skull that is part of the Chapter badge.
The Castellans of the Rift's Chapter badge is a white skull placed over a pair of crossed chains. The chains represent a symbolic barrier against the evil that these Astartes fight.
- Imperium Nihilus: Vigilus Defiant (8th Edition), pp. 75, 79, 86
- White Dwarf (October 2017), "Eavy Metal - Create your own Chapter," pg. 118