The Emperor's Gaze is an Imperial diplomatic vessel that was lost in the early days of the Achilus Crusade in the Jericho Reach. Indeed, it became subsumed by the space hulk Mortis Thule, yet somehow survived impact with that dreaded vessel, along with its crew.
The vast mass of Mortis Thule is made up of starships of all types, as well as spaceborne rock and other debris. It has long been noted that much of the wreckage of which the space hulk is composed is destroyed beyond any hope of the crew having survived the calamitous accidents that drew their vessel to its doom.
Very occasionally, however, a voidship caught up in the draw of the Mortis Thule survives the impact and melds into the hulk in such a state that many of its crew do too. Such was the rare example set by the Emperor's Gaze.
The ship was struck off of the crusade's fleet registry when it was determined that it had somehow become lost in the Warp.
Near the end of the 41st Millennium, however, doubts as to the ultimate fate of the Emperor's Gaze began to emerge, many of them voiced by the extended kin of the Navigator that was guiding the vessel through the Warp at the time of its loss.
In short, the Navigator's peers assert that had the soul of one of their own been claimed by the denizens of the Sea of Souls, then every other Navigator within a hundred light years would instantly have known of it and shared a portion of his torment.
After decades of searching, the Navigator's family have come to believe that that vessel must still be adrift somewhere within the Jericho Reach, though beyond this they have no solid theories.
- Deathwatch: Ark of Lost Souls (RPG), pp. 10-11