Faze V Uprising
In the wake of the Nephilim Schism, refugees fleeing the wars afflicting the southern galactic rim came upon a region of space usually wracked with Warp Storms. However now, the region was curiously calm and a joint expedition between Rogue Traders and the Dark Angels 5th Company was dispatched. Upon entering the orbit of Faze V, the fleet was immediately fired upon by orbital energy weapons of an unknown type. The Dark Angels combat dropped to the surface, discovering men altered by cybernetic arts and controlled by some blasphemous machine intelligence. The Dark Angels cut their way through the machine-slave hordes, smashing the the massive logic engines of the central intelligence.
Although they assumed they had freed the enslaved population, the captives craved continued communion with the machine. They rejected the newly installed rule of the Adeptus Terra. A massive uprising consisting of millions was launched against Imperial rule. The Imperium's response was predictably brutal, and the Dark Angels launched a grueling four month counter-insurgency campaign. The rebels were beaten back to their mighty silicon and fortresses and eventually wiped out entirely. However before departing Faze V, the Techmarines of the Chapter, accompanied by Grand Master Bekenel, entered the remains of the central machine intelligence and retrieved some scrap of undisclosed data. Though its contents has never been revealed, the Dark Angels left Faze V to burn.