The 13th Founding, also known as the Dark Founding, occurred sometime between the 35th and 36th Millennium, and is one of the very rare Foundings of Space Marine Chapters that were not recorded in exact detail. Since the Horus Heresy, the Adeptus Terra has maintained a bank of original gene-seed tithed by every single Chapter ever created, with one notable exception: the 13th Founding. There are no reliable records that indicate how many Chapters were created during the Dark Founding or what became of them. Full disclosure of the exact details of this mysterious Founding may lie buried deep within the record office of the Adeptus Terra. There are only two known Chapters that were Founded at this time -- the mysterious Exorcists and Death Spectres Chapters.
The exact nature of the Exorcists' creation and the gene-seed used in their Founding has remained classified by a special Bull Absolute of the Inquisitorial Representative issued at the time of their Founding. The Chapter has long-standing and strong links with the Inquisition and certain factions within the Ordo Malleus in particular, and it is most likely that it is the sponsorship and designs of that Ordo that has given them their unique character, and may well have specified their creation, either as a grand experiment or for some singular purpose. They are unusually resistant to both daemonic possession and Chaotic corruption. As part of their initiation into the Chapter, Exorcists Astartes are forced to serve as Daemonhosts for a short time before the possessing daemon is expelled back to the Warp by the intervention of an Inquisitor.
The Death Spectres are the second known Chapter to have been created during this unusual Founding. They are possibly a Successor Chapter of the Raven Guard as they share the same mutations as found in that Chapter's gene-seed. Like the Raven Guard, the Battle-Brothers of this Chapter possess a minor mutation that causes the Melanchromic Organ (which controls the amount of melanin in an Astartes' skin tone) to not function properly, leading to the development of albinism in Death Spectres Astartes. Differing Melanchrome gene-seed from Chapter to Chapter leads to variations in skin and hair colour, and in some Chapters all of the Space Marines may have identical colouration, such as is found in the albino warriors of the Death Spectres Chapter.
Select 13th Founding Chapters
|Exorcists||Classified by order of the Inquisition, believed to be the Grey Knights|
|Death Spectres||Raven Guard (Suspected)|
- Codex: Armageddon (3rd Edition), p. 18
- Codex: Eye of Terror (3rd Edition), p. 16
- Codex: Space Marines (5th Edition), p. 26
- Codex: Ultramarines (2nd Edition), p. 8
- Hammer and Bolter 2, "Exhumed" (Short Story), p. 30
- Heroes of the Space Marines (Anthology), "Headhunted" by Steve Parker, pp. 251-304
- Imperial Armour - The Badab War - Part Two, pp. 124-131
- Warhammer 40,000 Rulebook (5th Edition)