Edict of Nikaea
The Emperor's decree banning the use of psychic powers among the Legiones Astartes.
Historical Documents
Population and resource accounting of the most dangerous Imperial frontier.
The Imperial Census of Sector Obscurus, conducted during the 39th Millennium, represents one of the most comprehensive attempts to catalogue the resources and populations of the sectors bordering the Eye of Terror. The census was ordered by the Administratum to assess the region's capacity to support military operations.
Notably, many worlds listed in the census no longer exist, having been consumed by Warp storms or destroyed during subsequent Black Crusades.
After reading this, you'll understand: