Edict of Nikaea
The Emperor's decree banning the use of psychic powers among the Legiones Astartes.
Historical Documents
Surviving pages from Guilliman's masterwork on military organization.
The Codex Astartes, written by Primarch Roboute Guilliman in the aftermath of the Horus Heresy, established the organizational and tactical framework followed by most Space Marine Chapters to this day. These original fragments represent some of the earliest surviving copies.
The Codex divided the remaining Legions into smaller Chapters of approximately 1,000 warriors each, ensuring that no single commander could ever again wield the devastating power that Horus had turned against the Imperium.
After reading this, you'll understand: