Gabriel rally the remaining Blood Raven forces in the system on Niroot, a planet next to Cyprus Ultima. He plans to bring the Inquisitor to justice. However the Inquisitor was already a step ahead of him. During the battle of Acheron, the Inquisitor contacted the Imperial Guards and they have now arrived. The Imperial Guards has send a army to Niroot in order to wipe out Gabriel and the remaining Blood Ravens. While they fight each other, a Necron fleet lands on the planet and wipes out both sides. Gabriel loses his life in a duel against the Sand King, the Necron Overlord. The Necron then moves to Bal Ur , a moon within the system and the Guards continues to send armies after them. The Necron are able to fight off every Imperial Guard invasion with ease. To make things worst for the Guards. Gorgutz has his waaagh back and is assaulting Cyprus Ultima again. A detachment of the Imperial Guards are stationed at Ultima, allying themselves with House Varlock's forces to hold off the waaagh while the majority of the Guards focus on the Necron.
The system's sun suddenly becomes dark, revealing itself to be a artificial sun called the Black Sun that was built by the ancient Necron. The current Necron led by the Sand King hopes to find a artifact somewhere on the Black Sun so he could control a powerful Transcendent C'tan Shard imprisoned inside. The Imperial Guard follows the Necron into the Black Sun. A Blood Raven Fleet from Sub Sector Aurelia arrives in the system, it seems Gabriel has contacted them before his death. The Blood Ravens also descends into the Black Sun. The Ravens and the Guards made a truce in order to stop the Necron from reaching the artifact. However the crons proves to be too powerful for the two armies. Realizing they can't stop the Necrons head on, Tarkus led a band of elite space marine to find and destroy the artifact before the Necron can reach it. With it destroyed, the Black Sun releases the C'tan Shard that begins to wipe out the Necron, Imperial Guards, and Blood Raven forces. The Sand King tells the remaining survivors that they are doomed unless they can reactivate the Black Sun's defenses. The remaining Guards, Ravens, and crons must work together to find and activate the Black Sun's defenses in order to imprison the Shard again. The Sand King unleash his own personal Shard but this is only to buy time as the Sand King's C'tan Shard is nowhere as powerful as the one from the Black Sun. The devices were successfully activated and the Black Sun's C'tan Shard was sealed once again. The Necron leaves and the Imperial Guard and Blood Raven stays in the system. The Orks has been pushed back and Gorgutz has escaped. The Black Sun has been reactivated again bring sunlight to the planets. The Inquisitor is nowhere to be found