Astartes Praeses

The Astartes Praeses were founded as a group of Space Marine Chapters tasked with guarding the borders of the Eye of Terror. It is a difficult and unforgiving task; the chapters are constantly beset by the Traitor Legions and even the occasional Black Crusade. Originally numbering twenty Chapters, eighteen now remain because one went traitor and the other was destroyed. And then this happened.

The full membership of the Praeses is unknown, but the following 14 Chapters have been confirmed as being part of the Praeses:

• Angels Eradicant
• Black Consuls until they were (probably) destroyed. Confirmed to have been destroyed in a Hive City by Iron Warriors detonating the Hive reactors to prevent capture and rebuilt with Primaris Marines. Some forces were on the Achillus Crusade in the Jericho Reach and survived as well.
• White Consuls, their counterpart, (definitely) still around.
• Brothers Penitent
• Crimson Scythes
• Excoriators, who take Dorn's stoic endurance to the point of borderline BDSM.
• Iron Talons, known to flay the skin of their victims and drape it on their armor, Drukari\Night Lords style.
• Knights Unyielding
• Marines Exemplar
• Night Watch, notable for having one of the best names and color schemes in all the Adeptus Astartes.
• Reclaimers
• Subjugators, what the Black Templars would be if they were Codex compliant. Known for excessive use of force. Their homeworld is not so much near the Eye of Terror as in the route Abaddon is supposed to take to reach Terra.
• Viper Legion, a chapter so minor only 3 things are known about it.
• Fire Claws, until they went rogue (kinda, it's in the radical inquisitors sense) and renamed themselves the Relictors.

The Ultramarines Honour Company is sometimes numbered amongst them. It is not an actual Chapter, but is tasked with the same purpose as the Astartes Praeses.

Unconfirmed members

List of chapters that may or may not also be members of the Praeses:

• Sons of Malice - Participated in the 13th Black Crusade to reclaim their homeworld Scelus, a world in the Cadian sector. Which puts them existing exactly where you would want an Astartes chapter if you're trying to round up enough to guard the Eye of Terror. Shame about that whole being excommunicated and not-worshipping Malal thing.

Taking all of this into account, and assuming that the Black Consuls were the aforementioned destroyed chapter (before being rebuilt) and the Sons of Malice are the traitor chapter, and further assuming the Ultramarines Honour Company is not technically counted, that leaves 5 chapters that haven't been named.

The Wardens of the Gauntlet

With the Great Rift spreading warpfuckery over nearly half the galaxy, there is no longer any point in trying to contain the traitor legions to the Eye of Terror. Instead, what is vital now is to secure the few stable passages between what is now called the Imperium Sanctus and the Imperium Nihilus, or "Dark Imperium". To this end Roboute Guilliman ordered the creation a new fraternity tasked with ensuring the stability of the Nachmund Gauntlet, from Sangua Terra all the way to Vigilus, led by the Castellans of the Rift. This was supposed to be an organization not unlike the Maelstrom Warders, which pitted the Astral Claws, Lamenters, Mantis Warriors and Charnel Guard against whatever dared to come out of that other hellhole, but due to warpfuckery the message arrived piecemeal to the chapters.

The end result has been a piecemeal alliance of Space Marines that is yet to formalize. Some have sworn themselves to Nachmund's defense, while others... just happen to be there and willing to lend a hand.

• Castellans of the Rift: The leaders. They have established numerous outposts to coordinate the Gauntlet's defense.
• Necropolis Hawks: sworn themselves to the defense of the Nachmund Gauntlet.
• Sons of the Phoenix: Were on Vigilus from the War of Beasts and intended to go fight elsewhere, but decided to stay in Nachmund.
• Wrathhost: Purged an asteroid field that was infested with pirates of a dozen different species. Surprisingly (or perhaps not), the supposedly self-serving pirates fought with uncharacteristic cohesion and concern for their fellows. Turns out the whole mafia was being run by a water-caste Tau, somehow light years away from his supposed habitat in the Eastern Fringe.
• Salamanders: A company of the sons of Vulkan fought a Khornate warband of Night Lords so degenerate that the sallies had to paint their helmets black to bleach their eyes from the attrocities they witnessed.
• Kolossi of Kronos: One of the newest Ultima Founding chapters. They have managed to destroy three capital-class ships of the Black Legion... but at 4/5ths of their own fleet.