The Veiled Region is a vast unmapped area of Segmentum Pacificus that consists of dense nebulae and newborn stars that suffer from waves of radiation alongside discarded stellar matter whilst being cloaked in stellar dust. Within its expanse is known to reside a number of greenskin pirates, a race of sluggish primtive creatures on a dying world and a few xenos mercenaries as well as traders. Unknown to many, Necrons are known to populate this region of space.
Since the beginning of recorded history of the Imperium, this area had been referred to as the Veiled Regions. It is known that Explorator Fleets had barely probed the surface of its nebulae since the age of the Great Crusade thus there was only limited knowledge on this region of space. One Rogue Trader is known to had travelled on the outskirts of the Veiled Region before heading to the western edge of the galaxy with his records indicating his limited encounters with some alien species. The limited levels of navigation conducted of this region had been both dangerous and hazardrous with some such as Khrul believing that the reason it remained unexplored is because of the resources needed to penetrate it. Under Imperial law, it was prohibited for any Human settlements to be established within the Veiled Region. Despite this being the case, Human settlements within the Veiled Regions was a persistent yet unproven rumour. Amongst the greatest dangers of this area was its isolation with Astropathic communication being difficult as any psychic communication being reflected back and echoed with only silence being returned to them. Any exploration of the region was thus rarely attempted and never successful.
Baradrin Thaal is noted to had received Archeotech that he claimed he got from a Rogue Trader by the name of Devian who in turn acquired it from the Veiled Regions. The Adeptus Mechanicus were unable to discern this artefacts origin except that it was from a xenos civilization of advanced technological development. Thus, they decided to dispatch Archmagos Voar to finding its source in the Veiled Region and he in turn assembled an Explorator Fleet for this task of hunting down the alien creators of the mysterious mask. This fleet was headed by the flagship Antithesis that was formed from the Martian fleet and consisted of forces that Voar believed would have little trouble in their expedition into the Veiled Region. The fact that the mask resembled a Human led the Mechanicus to believe that Human settlements resided in the Veiled Region that were either under xenos domination or serving as allies thus Voar was tasked with liberating them whilst bringing them under the Imperium of Man. The expedition was within its second year when the Veil was penetrated as the Mechanicus Explorator fleet passed through light years of thickening nebulae and stellar clouds whereupon they went through the clear void of space.
During this time, the Soul Drinkers Chapter that had been declared traitors by the Imperium took their Space Hulk, the Brokenback, into the Veiled Region to escape persecution where it was noted that the area had not been explored by the Imperium for thousands of years. This saw them attempt to escape the Adeptus Mechanicus leading them deeper into the Veiled Region to the point that Chapter Master Sarpedon was informed that they were in unexplored space. At this time, the Necrons native to this area of space awakened from their slumber which forced the Adeptus Mechanicus to ally with the Soul Drinkers as well as the Human inhabitants native to the Veiled Region to combat this threat.