The Astartes Praeses are a group of twenty Loyalist Space Marine Chapters whose sole purpose is to guard the Eye of Terror in the Segmentum Obscurus. The ancient tome known as the Mythos Angelica Mortis makes a single reference to 20 Space Marine Chapters created from the unique gene-seed of those Primarchs who did not fall to Chaos during the Horus Heresy and who were charged with protecting the Imperial sectors surrounding the Eye of Terror and supporting Cadia and the Inquisition as needed. Although the brotherhood of Space Marines included in the Astartes Praeses originally included 20 Chapters, one has been destroyed by the Forces of Chaos and two other Chapters, the Relictors and the Sons of Malice, were both declared Excommunicate Traitoris by the High Lords of Terra. Though it should be noted, the latter Chapter is only suspected of being one of the original 20 Chapters mentioned in the Mythos Angelica Mortis. The truth of this matter may never be known for certain. The Astartes Praeses were evidently Founded anew rather than assembled from the remnants of the Space Marine Legions, like many of the other Second Founding Chapters, to reduce the possibility of corruption by Veteran Space Marines who had been exposed to Chaos during the fighting of the Horus Heresy.
Compiler's Note: This is a partial list of the Imperial military strength forming the containment force around the Ocularis Terribus. Communications difficulties and the secrecy of some Adeptus Astartes Chapters means that this should be considered little more than conjecture. Though no comprehensive list has ever been assembled, the current known and past members of the Astartes Praeses include:
|Black Consuls*||Ultramarines||Second Founding||31st Millennium|
|Excoriators||Imperial Fists||Second Founding||31st Millennium|
|Iron Talons||White Scars||Unknown||Unknown|
|Relictors (declared Excommunicate Traitoris)||Unknown (Presumed to be the Ultramarines and the Dark Angels)||Unknown||Unknown|
|Sons of Malice (declared Excommunicate Traitoris)||Unknown||Unknown||Unknown|
|Subjugators||Imperial Fists||23rd Founding or 24th Founding||41st Millennium|
|White Consuls||Ultramarines||Second Founding||31st Millennium|
*Reported destroyed 455.M41. Current status unknown.
- Codex: Eye of Terror (3rd Edition)
- Dark Creed (Novel) by Anthony Reynolds, pg. 45
- Legion of the Damned (Novel) by Rob Sanders, pp. 14, 21, 60, 74
- Architect of Fate (Anthology) by Sarah Cawkwell, Ben Counter, Darius Hinks, and John French