Astronomicon

The Astronomicon is psionic beacon that starships of the Imperium use to navigate through the Warp.

The Astronomicon is generated by the Emperor with the assistance of a "chorus" of psykers collected by the Adeptus Astra Telepathica. The Emperor draws energy from the psychic chorus and broadcasts it into the Warp, where it can be seen by Imperial Navigators and used as a reference point. The Astronomicon covers most of the Milky Way galaxy, but there are regions of the galaxy on the far side from Earth that are too far away for Navigators to detect it. "Warp storms" can also obscure the Astronomicon from Navigators whose ships are inside or on the far side of the disturbance.

The energy taken to maintain the Astronomicon drains the life forces of the psykers in the chorus. How long it takes them to die depends on the strength of the individual psykers, but many die every day, and the ranks of the chorus require constant replenishment. Psykers selected for the chorus generally have little control over their psychic abilities; psykers with more controlled talents are sent to become Astropaths or to other duties.