An Astral Spectre is a powerful entity composed of congealed psychic energy and Warp-stuff. When manifest in the physical world, these entities take the shape of incorporeal spectres: patches of moving darkness, unnatural mists boiling with flickering images, half-transparent figures that cast no shadow, and a host of other forms.
In the Imperium, psykers are feared not only for their strange powers but for the untold harm which can and often does arise when their powers are used carelessly. When the abilities of a psychically-active mind are wielded by those weak in faith or will, the psychic energy can congeal within the fabric of the Warp to form Astral Spectres. These malevolent shadow creatures attack humans and devour their soul–essence to replenish the psychic energy from which the Spectres were born.
Although Astral Spectres vary greatly in appearance, there are a few common characteristics that all such Spectres share. They are vaguely humanoid creatures composed of patches of semi–translucent shadow, and their presence unnerves all sentient creatures in their vicinity, often causing said creatures to experience psychic phenomena. Without fail, their forms are both vile and horrifying. They possess no solid physical form but wield a variety of psychic powers which allow them to interact with and harm material beings.
Spectres employ the full range of their psychic abilities in carrying out their evil plans. When pressed, Spectres first attempt to manipulate the minds of weaker opponents, causing them to interfere with or even attack their allies. Spectres almost always target psykers first, as they are far and away the greatest threat to a being of the Immaterium. When cornered, they either unleash their psychic powers in an all-out attack or attempt to possess one of their antagonists. Spectres are cunning and intelligent and always seek to take a host who is either capable of fighting his way out of the situation or one whose allies will be unwilling to attack him. Though Astral Spectres are far from the most powerful foe one may encounter in the Calixis Sector, they are amongst the most difficult to combat due to their nature as creatures of pure Warp energy.
Although Astral Spectres are sustained by a combination of stolen life energy and the psychic flux of the Warp, they seem to relish causing terror. They are drawn to fear and will expend great effort to cause it. Often, they will even place themselves at risk in order to terrify a victim by appearing before him in their true, nightmarish form. What benefit if any they derive from this fear is unknown.
Appearances of Astral Spectres are on the rise in the Calixis Sector. The reasons for this are many and varied. The violence and conflict in places like Tranch lead to a great deal of psychic energy being released when innocents are killed. Perhaps most significantly, the various Ruinous Powers seem to be turning their attention to the Calixis Sector and moving events in a direction intended to cause more chaos and death. One such Astral Spectre appearance involves the so-called "Alley Reaper" of Gunmetal City on the sector capital world of Scintilla.
- Warhammer 40,000: Rogue Trader (1st Edition), pp. 203-204
- Dark Heresy: Core Rulebook (RPG), pg. 350
- Dark Heresy: Creatures Anathema (RPG), pg. 111