The Diamor System was claimed by the Imperium during the Great Crusade and the System, particularly the capital world of Tourmalid, was heavily built up and today serves as a major staging area for the Imperial Navy in Segmentum Obscurus. During the 13th Black Crusade, the System was targeted by a major Chaos Space Marine invasion.
In the aftermath of Cadia's destruction, Daemon hordes materialized on every world in the Diamor System and overwhelmed the Imperium's forces stationed there, following the end of the Diamor Campaign. It is not known if any of the Imperium's forces escaped from Diamor, as contact with the System has now been lost.
- Topas — Astropathic relay station
- Ioline — Factory world. Reduced to irradiated wasteland in the Diamor Campaign
- Zircon Sprawl — Asteroid belt
- Diamor — Blue Giant sun
- 1: Black Crusade: Traitor's Hate, Chapter 1
- 2: Gathering Storm: Rise of the Primarch, Chapter 1: Revelation and Rebirth - Addenda Inquisitoria