Prior to this codex, variant Chapters (Iron Hands, Salamanders, etc.) were often restricted to specific characters or minor trait rules. The 6th Edition codex formalized this into . Players chose a Chapter upon army creation, granting specific universal special rules to the entire force:
: Included dedicated histories and fluff for the Ultramarines, Raven Guard, Imperial Fists, Salamanders, and Iron Hands. Black Templars 6th Edition Space Marine Codex Pdf
The book moved away from the 5th Edition's heavy focus on the Ultramarines, providing more balanced "screen time" for the other First Founding Chapters. Prior to this codex, variant Chapters (Iron Hands,