The Gurash Nebula

The Great Crusade
From its first discovery by the 816th Expedition Fleet of the Great Crusade, the Gurash Nebula of the Malagant Sector has presented no end of trouble for the Imperium's settlers. It was the Iron Warriors that first colonised the Gurash Nebula, seizing it from the tyrannical clutches of the Gurashan Ascendancy, a sinister technocratic dynasty of degenerate humans left over from the darkness of Old Night. While the Gurashani wielded dark technology of unknown and inhuman origin, the unstoppable resolve of the Warsmith Sarvok Ghronn of the Iron Warriors persevered, the 87th Grand Battalion cleaving through the technologically superior abominations, and claimed it for the name of Perturabo and the Imperium.

Established as a transitory outpost within the turbulent Malagant Sector, the Iron Warriors lightly fortified the Gurash Sub-sector to ensure that passing Imperial forces had a quicker route through what was otherwise, a difficult to navigate sector.

Before the Heresy
With the 816th Expedition Fleet advancing to claim other sub-sectors for the Imperium, a token guard of one hundred Iron Warriors and their Mechanicum allies were left behind to maintain order over what would soon be regarded as a backwater system. Unfortunately for the fledgling Imperial presence within the Gurash Nebula, the settlers chosen to inhabit the hostile worlds of Gurash were predominantly convicts and defectors, delegated to labor camps to mine the green crystalline lattices that seemed to exist on nearly every world within the sub-sector. Under the control of local Mechanicum forces, masterminded by Archmagos Akoryphos Ikephiax, these crystals were harvested in great quantities through backbreaking, brute labor that left much of the penal population embittered and resentful of their machine cult overlords. With the Iron Warriors being used as little more than glorified prison guards, quelling any potential unrest through brutal crackdowns and regular executions of dissidents across the worlds, the Iron Warriors themselves soaked up some of that resentment. As the unrest boiled to outright violence, several worlds, starting with Valdec, Korasine Prime, and the forgeworld of Graevan V, fell into open rebellion, casting off their overlords and declaring independence. By the time a retaliation force of Imperial Army, Iron Warrior and Skitarii contingents arrived, the rebellion had seized control of the vessels of these worlds and made flight, fleeing into the unstable regions of the nebula, where they quickly adapted to a guerrilla hit and run campaign of piracy and reaving.

The system in chaos, and the Iron Warriors viewed as nothing more than the glorified enforcers of Archmagos Akoryphos, it was the Iron Warrior Sergeant Tekrus Kohr that discovered the great deception being carried out by their Mechanicus allies. Discovering that Archmagos Akoryphos was in fact harvesting the crystals to refine them into power cells utilized by the alien technology of the Gurashan Ascendancy, effectively following in the footsteps of the Technocratic former overlords of the sub-sector. Sergeant Kohr relayed this information to the Fabricator Locum of the Malagant Sector, and had the Archmagos and all subordinate to him, excommunicated. Descending into war with their former Penal Rebel enemies, the Mechanicum were able to overwhelm the Iron Warrior forces initially. It was only the tactical ingenuity of Tekrus Kohr, declared the de facto leader of the Imperial Resistance, that the Iron Warriors and their Imperial Army allies were able to hold the Gurash Nebula for long enough for Imperial reinforcement to arrive.The arriving reinforcements came from the 727th Expedition fleet, a combined force of Sons of Horus and Word Bearers under Chaplain Adramakaul the Unblinded, who came under the guise of upholding Imperial interests, but had another agenda altogether. This dark purpose proved to be far more sinister than whatever even the Dark Mechanicum had planned.

The Horus Heresy
When the Dropsite Massacre occurred, the Iron Warriors under the newly promoted Captain Tekrus Kohr had little knowledge of the treason of their Primarch, only a few rumors, nefariously planted by Chaplain Adramakaul. Discontent soured the Iron Warriors even further as the Sons of Horus and Word Bearer forces stole the glory in the pirate hunting campaign against the Dark Mechanicum renegades,and reclaimed a dozen worlds for the Imperium, while the Iron Warriors were again, re-delegated to rebuilding the sub-sector's defenses and fortifying the Legiones Astartes positions.But even this discontent paled in comparison to what came next. Greeting the surprise return of the 816th expedition fleet as it approached the port-moon of Allusia Secundus, Captain Kohr was utterly surprised when Warsmith Sarvok Ghronn approached flanked by an allied Dark Mechanicum Explorator Fleet under the command of Archmagos Akoryphos. Confusion setting in, as allies seemed to become enemies, and vice versa, the 816th Expedition Fleet demanded entrance into the heavily fortified hollow port moon. When Captain Kohr, refusing to allow the Dark Mechanicum, after knowing their betrayal, in,disobeyed orders from his superior, the Horus Heresy was brought in full force to the Gurash Nebula. With little more than a hundred Iron Warriors, and some twenty thousand Imperial Army and still loyal Skitarii allies at his behest, Captain Kohr did what he could to repel the unthinkable attack of his superior officer. With the defenses of the Hollow Moon at his disposal, he made some original leeway, calling upon his Word Bearer and Sons of Horus allies to aid him.

After a week's worth of harrowing void siege, those allies did arrive, and Captain Kohr allowed them to enter the defensive ring of the port moon. And that was his final mistake. Chaplain Adramakaul and the Sons of Horus showed their true colors, and betrayed the loyal Iron Warriors, blasting through the defenses from within, and allowing Sarvok Ghronn and his traitor Iron Warriors into the port moon, thus claiming the most strategic location within the Gurash Nebula with one swift blow.