A Lady of the Voids is a Daemon of the Chaos God Slaanesh, Prince of Pleasure, encountered within the Calixis Sector that lurks between the stars, seeking a way aboard an unwary vessel traversing the Immaterium by preying upon a Navigator or Astropath. In a moment of weakness they can use an unfortunate victim to pass directly through a Gellar Field and into a vessel. When the daemon manifests, its true form is horrific and is often enough to break a mortal's mind. With many voices the creature screams and moans in a dreadful Warp-song which enraptures all who hear it -- compelling these unfortunate souls to mutilate themselves, destroy equipment, open airlocks into the void and murder one another.
In spacefarers' tales, the Lady of the Voids is the safe, oblique name given to a type of foul thing that lurks between the stars. They are the voices in the void, the witch–queens of daemons who desire only to sunder vessels and tear the living breath from crewmen's bodies with a kiss. Their call is a siren's song that can send men mad, struggling to open their compartments to space or killing one another with nails and teeth.
The daemons that give rise to these fearsome tales are a nameless Slaaneshi breed that is often part of the vile host that trails any voidship of the Imperium as it travels established Warp–routes. Unlike her lesser brethren who can merely follow the ship ineffectually, a Lady can prey upon a moment of weakness by the voidship's Navigator or Astropath, using it to pass through the Geller Field and enter the vessel.
To view the bursting of an Astropath's body and nightmare manifestation of a Lady of the Voids, draped in torn flesh and entrails like a cloak of rags, is enough to break the weak of will. The daemon appears as a merging of several female bodies about a vertical axis -- faces, arms, and mouths facing in different directions. Her torso is a hideous mix of woman, crab, and bloated toad, whilst half of her arms end in spiny pincers.
From the first, the Lady's many voices scream and moan in the patterns of the Warp. This dreadful Warp–song enraptures all who hear it, piercing the ears and numbing weak minds. To the enraptured, the Lady is a beauty to burn the soul -- sanity flees as the Warp–song melts the mind, and a foaming madness soon results. Some crewmen mutilate themselves; others turn to destroy tech–devices, murder one other, or struggle to open the vessel's seal–gates and let in the void. The daemon gleefully sweeps through the vessel at the head of a growing horde of the insane, set upon multiplying the suffering of her puppets in an orgy of destruction and death.
Many vessels have been lost to the Calixian Warp in this way. The Inquisition knows of this daemon breed from the few faithful souls to survive: Adeptus Mechanicus Tech–adepts who sealed themselves in insulated enginarium spaces, hardened Battlefleet veterans who banished the daemon by detonating a munitorium vault, and of course, Jagamar Elste.
- Dark Heresy: Creatures Anathema (RPG), pp. 123-124