In early 023M42 Inquisitor Esquerra had issued an edict for the Imperium to secure the Hecate Gap by taking the worlds of Ergura's Fall and Haven, while preparing to evacuate the Rifts of Hecate, closing the gap in the warp storms once and for all. In an agreement with Inquisitor Huron, also working in the Hadron Expanse, Huron would seek the remaining necron Nexus Arrangement in the Rifts of Hecate, oversee the withdrawal of imperial forces from the region, secure the necron Tomb complex on Haven where another Nexus Arrangement was holding the Hecate Gap open, and close the Gap.
The rationale for closing the Gap was clear. Although the Rifts of Hecate were rich in resources, the combined threats of tyranids, necrons and lately a powerful greenskin infestation put the Imperium at risk. Imperial forces were already overstretched and at the end of a tenuous supply line in 023M42, and Esquerra wanted to secure the Imperium's logistics before attempting a crusade into new or in this case long lost territories. Inquisitor Esquerra had left on urgent business elsewhere, leaving Huron to oversee events in the Hadron Expanse, but Huron had other ideas.
The tomb complex containing the Nexus Arrangement holding the Hecate Gap open had fallen into ork hands, but the orks as yet hadn't figured out the importance of their find. With the Imperial armies actually doing rather well on both Haven and Ergura's Fall, despite the supply situation, Huron made the unilateral decision to change Esquerra's edict, conquer both systems in the Hecate Gap, and move forward with the Crusade in the Rifts of Hecate.
To do this Huron, with one Nexus Arrangement in his possession, moved to Haven in order to scout out personally the situation around the necron tomb complex now in the hands of the orks. He didn't bother to tell any military personnel of the importance or even existence of the ancient xenos artefacts, reasoning that ignorance was the best defence. Unfortunately on this scouting mission, the Inquisitor and his retinue found themselves surrounded by orks of the Bloodfang tribe, who were now within touching distance of two of the most powerful artefacts in the sector. Huron called for immediate extraction, and forces were scrambled to his location in order to hold a perimeter long enough to rescue him and his important artefact.
Many imperial units rushed to his aid including the Sisters of Battle, Dark Angels (including what appeared to be the chapter master himself) as well as hastily diverted Leman Russ battle tanks from a Librian mechanised regiment. Fierce and confused fighting erupted with the Imperium calling in bombardments as the orks swarmed the location, while even the tau, surprised by the commotion, sent their own air force to inspect the action. A number of quite baffling events characterised this engagement, including the unexpected behaviour of the ork Shokk Attack Gun, which at one point managed to replace an entire Leman Russ crew with snotlings. This initial success was somewhat damped from the ork perspective as the snotlings then began operating the tank for the Imperium. Later, the ork warboss was infected with a "madboy" virus, confusing him long enough for him to be slain in combat, while Inquisitor Huron's attempt to use Xenos technology in the form of a man portable railgun was less than effective.
Fortunately for the Imperium, the perimeter held long enough to see the extraction of all important personnel, and critically the evacuation of the Nexus Arrangement in the Inquisitor's possession.
With the ork strength now understood, Huron immediately convened a council with General Maximus. The focus was the Greenskins and the necron tomb complex. All available forces including the reserves were deployed at Haven with one aim, to force the orks back. If they failed, Haven and Huron's mission would lie in tatters, as would control over and access to the Nexus arrangement holding open the Gap. Success would put the Imperium in pole position to fully conquer both worlds and continue the Crusade both Huron and Maximus dearly wanted.
Against the horde of orks including the mighty war engine "Hope Killa" were arrayed the forces of the Novgorod Guard, an entire Knight Lance and a force of Adeptus Custodes. The battle raged over the southern plains of Haven as the Imperium pushed north from their second bridgehead. Casualties on both sides were vast and the orks, having numerical superiority were able to systematically wear down the imperial left flank, where desparate fighting took place to hold off an ork counter attack. This imperial flank eventually gave way, but the time bought by this valiant stand allowed the Knights and Adeptus Custodes to throw themselves into the middle of the ork horde in the centre of the front the imperial mission had created. Most of the Knights were lost in the melee, but on the right flank the Imperium secured their objectives, and in the centre the sacrifice of the imperial war engines was not in vain. the orks were gradually exhausted to the point where the Bloodfang tribe retreated to avoid being encircled and annihilated.
With the main action over both sides counted the cost. The Imperium were now in control of nearly 40% of the world and were now the preeminent faction on Haven. One more push against the greenskins and Haven would fall to the Imperium.