Cairn Gruach

**Cairn Gruach** is an Adeptus Astartes Chapter Homeworld of the Iron Arbiters Space Marine Chapter located in the Segmentum Solar in the Anakitis Sector.

## Background

Cairn Gruach is an eerie world. Its name is taken from the true identity of a character attributed to one of the long-forgotten plays of the ancient dramaturge Shakespire, a scheming and malevolent figure with ruthless ambition who manipulated many for her own gain. At the time of the early Great Crusade, there was a dread warlord north of the Sol System, a tyrant and despot who held dominion over dozens of worlds. She was laid low by Horus Lupercal himself, and his Luna Wolves Legion finally defeated her forces upon this shrouded world. Her followers buried her there, within a colossal mound of stones. And thus the world is named Cairn Gruach, to honour the warrior who the Warmaster regarded as a worthy opponent. And so it was forgotten, for millennia, and the evil that slumbered there was left out of sight.

As the body of Gruach decayed, her soul did not. Instead of dissipating into the Sea of Souls as most do, it lingered, persisted. Gruach was what the Inquisition would call a Beta-class psyker, or even Alpha-class, if one were to be pessimistic. And so she remained, dwindling in power, resisting the pulls of the Ruinous Powers, thrashing and screaming for all eternity. But in the 36th Millennium, a Chapter of Space Marines called the Vermillion Ravens came to the world and made it their own. They built a massive basalt fortress, which they named Haemus Mons, and which they called home. Within a year, all of the Chapter's Librarians began to have the same, repeating visions of a slumbering darkness and mist-wreathed, long-haired shadowy figures watching them as they slept. It began with the least psychically potent individuals, as they were weakened, and their minds broken down by attrition. In time, all the Librarians found excuses to spend time off-world, but in time they returned. They always returned.

But Chapter Master Orkada Erythros began to experience significant trouble a mere decade after taking the world, when Haemus Mons was all but newly built. One-by-one, his Librarians all disappeared. Desperate for answers, he ordered his warriors recalled to Cairn Gruach from across the stars to find his lost psykers. The hunt began, and weeks past, and no trace was found. The entire Chapter scoured their world, and found nothing; and Erythros feared daemonic taint. As his position was privy to knowledge of the Imperium's greatest defence, he contacted Titan, to find that a strike force of Grey Knights were already en route. They arrived, and were immediately assailed by psychic visions of a world shrouded in darkness like smoke, and figures that came for them in the night. But the Emperor's final gifts remained resolute, and they refused to bow.

Within two days, they had pinpointed the location of the lost Librarians. And so Grandmaster Belphegor and Chapter Master Erythros led a joint task force into the cairn where Gruach's soul resided, in an isolated mountain range in the far north of the planet. And when they entered, they found each of the Chapter's twelve Librarians in various states of decay, some withered away to bones inside their armour, and others still flesh and blood, each dead and lying in ritual positions. And in the centre, a mass of coalescing life force formed from writhing shadows in the shape of a dark figure, stood Gruach. Erythros and Belphegor ordered their men to destroy her, but with a flick of her blurry fingers, they were torn asunder, blood spurting from ripped ceramite. The two heroes charged forward, and they grappled with the figure, and at the climax of the ritual she summoned enough power to draw the souls of every one of the Vermillion Ravens on the planet, and each were consumed, and Erythros lay dead on the ground. But Belphegor did not give up, and he shattered Gruach's essence at the cost of his own life. On a distant world, a bell tolled one thousand times. Gruach's soul was shattered, and each of those of the Vermillion Ravens laid to rest.

And so the last fragments of Gruach still haunt her world - half-glimpsed spectres upon distant mountainsides, the shadow that follows a tribal warrior gone off-path alone, the looming presence in the night. But as long as she is contained, she is harmless. Cairn Gruach is a world of dreams and madness. It is mountains that scrape the thin white sky, and craggy heathland. Spines of peaks spiral out into haunting patterns, and the howls of distant ghostly predators echo with the wails of banshees like the gheists of tangible sounds. Piles of stacked rocks - cairns - litter the landscape, mounds to the honoured dead and to ward off the evil spirits that haunt the world. Arctic tundra stretches, veiled by mist and shadow, into the icecaps. Frigid grey seas cover much of the surface that is not mountains and slopes littered with tall pines and dense forests. It is a dark place.

The people of Cairn Gruach are a hardy lot, adapted to live beside the remnants of an inhuman horror. They are hardly known to the wider Imperium, not even deemed significant enough to be civilised, or subjected to tithing. To say that they are phantoms themselves in that manner is an accurate assumption. They exist in a constant state of hunting and gathering, nomads with little land to farm. Some possess rare bronze or iron tools, but most are still locked within a stone age. They make ideal stock to recruit from, but only a handful have ever become Space Marines, for no Chapter has been on the world long enough to culturally integrate. Though an initial batch has already been taken by the Iron Arbiters, the traditions of the recruitment of each of the clans and tribes has yet to be truly established. Haemus Mons is the fortress atop the highest mountain on Cairn Gruach, of the same name. When the Iron Arbiters found it, it was desolate, full of dusty corridors and unpolished statues of Sanguinius, Primarch of the Vermillion Ravens.

Entire wings had been taken over to cobwebs, but thankfully due to its nature, it had survived the many years since last being inhabited. And so they began to make it their own - gothic shrines to Sanguinius replaced by boltgun racks, tall windows modified to allow screens and control consoles, spires transformed into weapons mounts, and the grounds of the fortress properly fortified with buttresses and one main gatehouse. The armoury took the colossal dungeons below Haemus Mons for their forges and their hangars, an entire great hall for the sarcophagi of dreadnoughts to slumber in stasis. The Apothecarion chose the easternmost wing, a low squat affair with much capability to host houses of healing and gene-research, but the Librarius positioned themselves on the north spire, taking up the ancient libraries therein, but also saw it as their duty to guard the last remnants of Gruach. Each company took a section for their barracks, training rooms, etc; and the Chapter Command decided the top reaches would be there. Venteel took an ancient throne room as his own, and ruled the world from a mighty obsidian throne.

Gruach is also noted to contain the small and barren world Nidavellir, home to a Kinhold of the Hyrthka-Wyrm Syndicate. The "Squats", as they are pejoratively termed, seem to hold no particular hatred for the Imperium or their Human cousins. To the contrary, a shaky alliance has existed between High Kâhl Andvari and Chapter Master Venteel since arrival into the system, whereupon a brutal war was fought with Aeldari forces seeking to gain a foothold on the shadowy world. The Kin of the Syndicate are stubborn, grudging, but loyal to a fault and have yet to go back on their oaths. However, an issue remains. Venteel's track record of attempting to negotiate with his would-be enemies were he following traditional Imperial dogma has only been increasing over the past months, and treaties with Nidavellir may truly be the spark that lights the flame that burns down the Chapter in the fires of the Ordo Astartes.