The Halo Stars are the scattered, isolated suns that lie beyond the fringe of the galaxy's great spiral, strewn across the lonely dark of the galactic halo where stars grow sparse and the void grows deep. Remote and largely beyond the reach of the Imperium, this desolate frontier is a place of mystery, rumor, and half-glimpsed horror.
Because the Astronomican, the psychic beacon projected from the Golden Throne, grows faint and unreliable at such extreme distances, travel among the Halo Stars is perilous in the extreme, and few expeditions that venture into the dark ever return. The region is spoken of as a haunt of ancient and terrible things, of lost human colonies gone strange in their isolation, and of xenos powers that dwell far from the light of the galactic disc.
To the Imperium the Halo Stars represent the very edge of the known, a boundary beyond which its authority dissolves into darkness and uncertainty, remote kin to the dread reaches of the Ghoul Stars. What secrets lie among those distant suns, what threats gather there unseen, none can say with confidence. The region endures in the Imperial imagination as a fearful unknown, a reminder that for all its vast dominion, humanity clings to only a fraction of the galaxy, encircled by a night full of things it cannot name.