Warcry: Varies - Assumed No Official Warcry.
Founding: 13th Founding - Dark Founding.
Successors of: Officially Unknown; their gene-seed is drawn from both the Grey Knights and the Imperial Fists.
Successor Chapters: None by Order of the High Lords of Terra.
Number: Records Inadequate. Suspected to be under 2,000. Actual number is between 2,000 and 3,000.
Primarch: Officially Unknown. They have two progenitors: The Emperor of Mankind, and Rogal Dorn.
Chapter Master: Exarlious 'The Grim'
Homeworld: Fleet Based. Recruits come from multiple Feral Worlds and Death Worlds along the Eastern Fringe as well as from the Black Ships.
Allegiance: Imperium of Man.
Colours: Black with Deep Greens and Deep Blues.

During the 13th Founding – otherwise known as the Dark Founding – a select set of members from the Inquisition, particularly the Ordo Hereticus and the Ordo Malleus, were set on establishing and maintaining a stronger presence in the galaxy’s eastern realms, particularly along sections of the Eastern Fringe. They argued that their forces were insufficient in the eastern regions of the galaxy, but at the time, the truth of it was never given any serious consideration. The excuse was a cover for their real intentions which was only known to a select few.

The purity of the Grey Knights gene-seed is unparalleled among and of the Adaptus Astartes, though it proved to be non-conducive of using as a genetic template for Successor Chapters. The select council responsible for started this project – whose identities were never discovered – sought to purify a chosen gene-seed stock by merging the Grey Knights gene-seed with their chosen gene-seed stock. There were several candidates for the gene-seed stock that was to be paired with that of the Grey Knights, chief among them were Chapters such as the Space Wolves whose gene-seed is plagued by genetic flaws. Bonding the gene-seed of the Grey Knights with some of the more flawed gene-seed stock proved unsuccessful, the council eventually bonding it with the gene-seed of the Imperial Fists.

The resulting gene-seed was found to be incredibly stable with perks and drawbacks from both origins present. The combined gene-seed never allowed for the reintroduction of the Belcher’s Gland, but did allow for the Sus’an Membrane to be re-introduced. The gene-seed also allowed for an increased prevalence of psykers and a resistance to psykic corruption – particular at the hands of the Ruinous powers. The prevalence of psykers and the resistance the corruption is not close to that of the Grey Knights, but well beyond what is typically found in any other Chapter.

Once the Chapter was at full strength, their founding was considered complete. The council that had conceived of their creation had long since died and no records were ever officially found. Known only to each Chapter Master through methods undisclosed are the secrets to their gene-seed and the project that led to their creation. It is a set of secrets that is very closely guarded by the Chapter Master, and nobody else within the Chapter let alone the Imperium knows of the existence of these secrets let alone their subject matter.

As with many of the Chapters established during the 13th Founding, very little was actually recorded beyond their basic Chapter details such as their title and colours. One of the few details that was retained was the region in which they were originally intended to operate. Their unique gene-seed has proven to be something of a curiosity and throughout their history, with genetic comparisons made in attempts to determine the Chapter to whom they owed their gene-seed yielding often odd and sporadic results. This meant that there was no way of predicting the potential short and long term flaws of the gene-seed were. This fact combined with the Chapter’s prevalence of Psykers and their resistance to the touch and corruption of the Ruinous Powers led to their gene-seed being restricted to renewing the Chapter’s numbers, meaning that the gene-seed was expressly disallowed for the purposes of forming Successor Chapters.

For reasons quite different to those originally conceived, the Chapter was given their fleet and sent to the eastern region of the galaxy where they began patrolling, their efforts focusing more towards Ultramar along the Eastern Fringe, though their reach has been known to extend beyond that. As time went on, the attitudes of the Chapter changed with regards to their abilities to properly fulfil their duties. They became less codex-compliant, expanding their numbers and altering their structure – these changes occurring over the course of nearly a thousand Terran years and the tenure of two Chapter Masters. These changes were predominantly encouraged and forcefully enacted by the Chapter Masters, both of whom drew inspiration from their patron Chapters as well as other Second Founding Chapters drawn from the Imperial Fists gene-seed. They both felt that the inspiration for these changes should be drawn from many sources, but kept in keeping with their heritage. As a result, the changes were inspired by many Chapters, predominantly the Grey Knights and Imperial Fists, but also many other Successor Chapters, the most notable of which being the Black Templars. How exactly the preceding Chapter Master convinced his successor to continue the changes he had set in motion is a secret as well guarded as the secrets of their origins, but he nevertheless managed it. The exact nature of the changes is not officially known due to the Chapter being fleet-based patrolling a region of space so far out where the Imperium’s ability to keep track of the Chapter in detail is strained at best.

Over the next three thousand or so years, the Chapter began crusading against the Ruinous Powers and, once their numbers had unofficially breached the two thousand mark, they also began actively trying to repel Tyranid splinter fleets. The practice of actively seeking out the Tyranids was eventually limited after suffering unacceptably large losses during their first attempts – their close succession disallowing the proper renewal of their numbers.