The Grail Abyss is a desolate streak of territory at the extreme northern border of the Imperium of Man. It is a celestial wasteland locked between two galactic spiral arms where stable star systems are scarce and rogue planets, energy bleed-outs, cosmic detritus and other navigational hazards are many. Sparsely populated and remote, it makes for one of the most dangerous regions of the Segmentum Obscurus. With the more populous sub-sectors of the Cyclops Cluster and the Manachean Commonwealth, the Coronid Reach and the Mechanicum-controlled domain of the Cyclothrathine Holdfast, the Grail Abyss constitutes one of the regions of the wider Coronid Deeps. Its history is closely linked to that of the famed 7th Expeditionnary Fleet of the Dark Angels Legion of the Legiones Astartes under comma