The 23rd Founding of Space Marine Chapters, also known as the "Sentinel Founding," occurred during the latter part of the 37th Millennium. Imperial scholars believe that the 23rd Founding was one of a series of linked Foundings that took place during this tumultuous period in Imperial history and that they were intended to repair the power and reach of the Adeptus Astartes that had suffered considerable losses in the preceding millennia.
According to the Requiem Malesent of Saint Kybra, no fewer than 57 Space Marine Chapters had been destroyed, turned Renegade or declared lost in the Warp during this troubled period. The era had been marked by such calamities as the Age of Apostasy, the disastrous 21st "Cursed" Founding, the attacks of the Forces of Chaos and a rampage of Orks almost unchecked along the Imperium of Man's frontiers.
Several of the Space Marine Chapters Founded at this time were conceived as Chapters that would pursue perpetual Crusades against the Emperor's foes. They were created from the most stable gene-seed stocks available to the Adeptus Mechanicus. The Marines Errant is one such Chapter created during this time. Further details of this Chapter's origins can be found in the Mythos Angelica Mortis, the great work concerning the Space Marines of this age, which lists five such new-Founded Crusade Chapters and their blood-progenitors.
The Marines Errant are recorded as having the Eagle Warriors Chapter as their immediate forebears. The Eagle Warriors' gene-seed was drawn from the Ultramarines' lineage, although why the Eagle Warriors in particular were singled out for the honour of a "named" Founding being drawn from their ranks remains lost to posterity.
The Star Phantoms were also created during this Founding to aid the Imperium's defences in numerous ill-starred and vulnerable areas of the galaxy. Their exact origins and progenitor Chapter remained mysterious even during their creation, as did the backgrounds of many of the Chapters of this Founding.
Some Imperial sources have since hinted that the Star Phantoms were Founded utilising Dark Angels gene-seed, although this has been vehemently denied by the Dark Angels themselves, and the Star Phantoms consider such queries, even via official channels, as inherently presumptuous and cause for offence. Likely this speculation is simply based on some observed similarity in livery, iconography and trappings between the two Chapters, which has given birth to an assumption about the Star Phantoms' origins by certain scholars of the Adeptus Terra and Departmento Strategos.
Another Chapter created during this time was the Imperial Harbingers, but like their fellow Astartes of this Founding their exact progenitor Chapter remains unknown.
The Steel Cobras were a formerly Loyalist Chapter of the Adeptus Astartes that was created during the 23rd Founding. Unfortunately, their blasphemous worship of the Emperor of Mankind as an animal totem prompted a puritanical Crusade against them by the Ecclesiarchy, led by a particularly bombastic Cardinal. Faced with such an assault by the Imperium, the Steel Cobras turned to the service of Chaos to gain the power needed to defend themselves.
Select 23rd Founding Chapters
|Imperial Harbingers||Unknown||Unknown||Birmingham||The Imperial Harbingers were created to help replace the considerable losses suffered by the Adeptus Astartes in the preceding millennia. Along with several other Chapters, the Imperial Harbingers were from the outset conceived as a replacement Chapter that would spend its existence on continuous Crusade and was to be created from the most stable gene-seed stocks available. The Imperial Harbingers hail from the Feral World of Birmingham, "the Black Planet," so named because it receives very little visible light.|
|Marines Errant||Eagle Warriors||Roboute Guilliman||Vilamus (gene-seed repository)||The Marines Errant were created to repair the gap left in Imperial military forces by the loss of other Chapters. The Chapter was well-named, for over the millennia since their Founding, the Chapter's Battle-Brothers have been active throughout the entirety of the Imperium and often far beyond its borders. The Chapter has shown a tremendous resilience and flexibility that have allowed it to participate in a broad range of Imperial Crusades even while its Battle-Brothers fervently venerate the dictates of the Codex Astartes.|
|Star Phantoms||Dark Angels (Suspected; Unconfirmed)||Lion El'Jonson (Suspected; Unconfirmed)||Jahga||Created to replace heavy losses sustained by the Adeptus Astates, the Star Phantoms were one of several Chapters whose mission was to take and hold various xenos-contested regions on the very borders of the Emperor’s domains. Many of the Chapter’s earliest campaigns were waged against now-extinct xenos monstrosities, and the Star Phantoms frequently operated on their own and far from the support of other Imperial institutions. The Chapter’s rites and traditions focus on death and martyrdom, the fallen being revered over and above the living. Symbols of death and mourning are used as Chapter iconography.|
|Steel Cobras||Unknown||Unknown||Tukaroe VII||The Steel Cobras were a formerly Loyalist Chapter of the Adeptus Astartes whose blasphemous worship of the Emperor of Mankind as an animal totem prompted a puritanical Crusade against them by the Ecclesiarchy, led by a particularly bombastic Cardinal. Faced with such an assault by the Imperium, the Steel Cobras turned to the service of Chaos to gain the power needed to defend themselves. They are known to have established a base of operations deep beneath the ammonia seas of the frigid world of Tukaroe VII. Although the Imperium is aware of these Renegades' existence, nothing short of an invasion by an entire Loyalist Space Marine Chapter is considered likely to dislodge them from their fortified seabed bunkers.|
- Adeptus Astartes: Successor Chapters (Limited Release Booklet)
- Battlefleet Gothic Rulebook, "To Cleanse the Stars"
- Codex: Eye of Terror (3rd Edition), pg. 16
- Codex: Space Marines (3rd Edition), pp. 44, 76
- Deathwatch: Honour the Chapter (RPG), pp. 42-49, 117-118
- Deathwatch: The Emperor's Chosen (RPG), pg. 54
- Deathwatch: The Jericho Reach (RPG), pp. 18-19
- How to Paint Space Marines (2004), pg. 89
- Imperial Armour Volume Two (Second Edition) - War Machines of the Adeptus Astartes, pg. 52
- Imperial Armour Volume Nine - The Badab War - Part One, pp. 26-27, 30-31, 39, 74-81
- Imperial Armour Volume Ten - The Badab War - Part Two, pp. 23, 44, 47-49, 53, 55, 132, 134-135, 180
- Imperial Armour Volume Thirteen - War Machines of the Lost & The Damned, pg. 25
- Index Astartes IV, "Rogue Sons - Renegade Space Marine Chapters"
- Insignium Astartes: The Uniforms and Regalia of the Space Marines, pg. 54
- Warhammer 40,000: Cities of Death (Supplement)
- Warhammer 40,000: Compendium (2nd Edition), "The Badab War", pp. 33-35
- Warhammer 40,000: Planetstrike (5th Edition), pg. 57
- Warhammer 40,000 Rulebook (5th Edition)
- White Dwarf Magazine #101 (UK), "Index Astartes: From The Imperial History Archive - The Badab War: The uniforms and history of the Badab Uprising" (1988) by Rick Priestley, pp. 71-73
- White Dwarf Magazine #249 (UK), "Index Astartes - Emperor's Shield"
- Angels of Darkness (Novel) by Gavin Thorpe, pg. 80
- Armageddon (Anthology) by Aaron Dembski-Bowden
- Blood and Fire (Novella) by Aaron Dembski-Bowden
- Blood Reaver (Novel) by Aaron Demski-Bowden
- Soul Hunter (Novel) by Aaron Demski-Bowden
- Legends of the Space Marines (Anthology), "The Trial of the Mantis Warriors" by C.S. Goto
- Flesh of Cretacia (Novella) by Andy Smillie
- Third War for Armageddon Worldwide Campaign - Forces Disposition, Imperial Forces: Celestial Lions