The Nachmund Gauntlet is the only confirmed navigable passage in realspace through the Great Rift which has cut the galaxy in half since the end of the 13th Black Crusade in 999.M41. Yet the Nachmund Gauntlet brought little hope to the Imperium of easy access to the territory of the Imperium Nihilus.
The gauntlet crossed space through the barrier of the Great Rift from the world of Vigilus in the Imperium Nihilus to the planet of Sangua Terra in the Imperium Sanctus, the half of the Imperium of Man still accessible to the light of the Astronomican.
The Nachmund Gauntlet was maintained by the large spears of polarised blackstone ore found within the planetary crusts of Vigilus and Sangua Terra, whose anti-psychic effect acted to push back the effects of the Warp rifts pressing against the gauntlet from either side.
The Cicatrix Maledictum had at least one gap, though others have been reported but not confirmed. The passage was located near the great Warp rift known as the Eye of Terror, which had been avoided by Navigators since the Great Crusade, for Warp Storms and strange anomalies have always made the region too dangerous to travel.
There, when the swirling nebula lulled, was revealed the Nachmund System. The Tyrant King of its primary planet of Dharrovar, Kaligius, ruled over the Renegade Knights of House Mandrakor who had not been seen since the Horus Heresy. Claiming Old Night had returned, Kaligius rejected all communication with the Imperium, instead forging pacts with Renegades and pirate fleets. Some Imperial starships have run the Nachmund Gauntlet successfully, but many more have been destroyed attempting the journey -- the ruined hulks of innumerable voidcraft now hang suspended in space as a vast starship graveyard.
Once considered cautious, the king's behaviour became ever more paranoid and erratic, and it was said he protected his holdings with the ferocity of an enraged drake. His defenders claimed he was like that with good reason, for on either side of the Nachmund Gauntlet was a seething tide of Chaos that constantly sought to break its metaphysical bonds and spill into realspace.
At the dawn of the Great Rift, starships that sought safe passage through the gauntlet had no choice other than to pass near Dharrovar. Those who gave the planet a wide berth were allowed to slink past without interception. Those who sought safe haven or attempted to contact the Knight World under a flag of parley were treated with hostility, suspicion or even violence.
A staunch independent, Kaligius was already convinced that no good would come from allowing the Imperium to draw him back into the fold. Instead he turned to tyranny and oppression. Even as the term Imperium Nihilus was coined, he was declared Excommunicate Traitoris.
Lord Commander of the Imperium Roboute Guilliman despatched the Castellans of the Rift, a Space Marine Chapter raised during the Ultima Founding, to drive back the hordes of daemonic war machines and Renegade Knights blighting one of the only stable routes through the Cicatrix Maledictum.
At least two companies of the Castellans of the Rift eventually deployed to fight the daemonic legions besieging Sangua Terra on the Imperium Sanctus side of the gauntlet.
On the far side of the Nachmund Gauntlet lay the Hive World of Vigilus. Control of Vigilus allowed the Imperium to just barely keep its beleaguered worlds in the Imperium Nihilus on the far side of the rift reinforced and re-supplied; to lose it would cripple the war effort against the rampaging forces of Chaos.
Vigilus also provided a vital staging ground for the billions of refugees that come through the Nachmund Gauntlet to escape the threat of Chaos or worse in the Dark Imperium.
In time, because of its strategic position, Vigilus became coveted by several of the factions of the galaxy, and the conflict known as the War of Beasts erupted on its arid surface.
Creation of the Nachmund Gauntlet
Noctilith stone, also called blackstone, had a peculiar property that, to those who understood the nature of the cosmos, made it more valuable than any other resource in the galaxy.
Blackstone was Warp-resonant, and could be charged either to attract or repel empyric power.
The spear-like deposits in Vigilus' crust had been polarised to repel Warp energy by some ancient xenos technology. It was these that were holding back the Great Rift around Vigilus -- and indeed, by creating a channel of anti-Chaos force between the Imperium Nihilus and the Imperium Sanctus, forming the Nachmund Gauntlet itself.
The planet of Sangua Terra had the exact same spears of blackstone in its crust, held in a strange black suspension that meant they always pointed towards Vigilus.
The anti-empyric field that thrummed between these spears kept the Nachmund Gauntlet open.
If Abaddon the Despoiler succeeded in destroying that esoteric resource, the Warp Storms around the Nachmund Gauntlet would close in, and the corridor of safe passage would be subsumed completely, leaving the Imperium Nihilus to the mercies of the forces of Chaos.
It was for this reason that the Despoiler and his Black Legion were so determined to seize or destroy Vigilus and its counterpart on the other side of the gauntlet during the early years of the Era Indomitus.
- Warhammer 40,000: Rulebook (8th Edition), pg. 53
- White Dwarf (October 2017), "Eavy Metal - Create your own Chapter," pg. 118
- Wake the Dead: Lore
- Imperium Nihilus: Vigilus Defiant (8th Edition), pp. 5, 11, "To Run the Gauntlet"
- Imperium Nihilus: Vigilus Ablaze (8th Edition), pp. 26, 44