Cybixx completes the Mallem Cybixxum

The knowledge of the battle station being built by the Adeptus Mechanicus of Cybixx was soon leaked to the loyalist faction through Hathek's spy and surveillance network. Hathek, "suggesting" to the Ultramarines that the battlestation may be heretical, the astartes despatched a company strength force to Vandrax to investigate. Their strike cruiser held on board a team of Hathek's loyalist Adeptus Mechanicus, who declared the battlestation, known as "Mallem Cybixxum" to be heretical and of Xenos origin. Enraged by this, the Ultramarines landed on Vandrax itself, demanding that Cybixx hand himself over to the Inquisition. Unaware of the wider Crusade implications and the ongoing disagreement between Vorushko and Hathek, the Ultramarines were naive in expecting Cybixx to comply. Without explaining to them, Cybixx launched a carefully calculated assault on the astartes.

It was Cybixx's intention to leave no marine alive, but a small number of devastator marines and at least one officer of the investigating company managed to disengage and escape from the ferocious battle which developed. Fleeing rapidly, the ultramarines broadcast plans of the space station to Hathek and his allies. 

Vorushko intercepted the astropathic signal intended for Hathek and sent her own urgent message back to Cybixx, demanding confirmation that the battle station had been built in line with their plans to close the Foramen Secundus. From Cybixx there was no reply.