Right: I have added the following to the IA.
It does not yet constitute a culture for the chapter, or a comprehensive outline as to how-they-were, but its a start:
Being a fleet-based chapter, the Oath Keepers set about securing recruitment rights over a number of suitable worlds, mainly on the borders between the Segmentums Pacificus and Obscurus. On three of these worlds, Techmarines uncovered evidence of ancient human civilisations. The feral inhabitants of each planet possessed no knowledge of these once great cities, the ruins of which dotted the polar caps. Research indicated that these technologically advanced civilisations pre-dated the Imperium by many millenia. Uncovering three such planets had a dual influence on the Oath Keepers. On one level, it further invigorated a sense of the Imperium's superiority - a line of thought that was zealously preached by the Chaplaincy. Yet the memory of the Scouring and the Heresy remained raw. The discovery also instilled in the brotherhood a sense that for all its greatness the Imperium was clearly vulnerable - it was magnificent but not invincible. That, after all, had been the reason for the creation of the Adeptus Astartes. In the light of subsequent events, it is feasibly that this exerted a prominent influence on the Keepers' chapter cult. Certainly many of tapestries and murals within the halls of the Act of Conscience depicted scenes of what these civilisations were imagined to be, with the visage of the Emperor looking on in dismay, in full knowledge of their shortcomings, and with the image of lion looking over his shoulder to symbolise the Keepers' Primarch - as yet unborn but ever in the mind of the Emperor.
The chapter's first opportunity to incarcerate one of the Fallen arose in M33. A long-planned and carefully nurtured uprising had been nursed by small Chaos warbands that were initially believed to hail from the Alpha Legion. Entire Imperial Guard regiments had been turned, from the subsector Purgatio. Bribes, threats and other methods of subterfuge had delayed the Administratum from noticing a steady reduction in tithes. When treachery was revealed, the entire subsection had fortified itself against retribution. The Oath Keepers responded. They dispatched a powerful crusade, working in close concert with the Halo Shields - a successor chapter of the Imperial Fists (LIbrarium note: unlike other allies in this IA, the Halo Shields are also a DIY faction).
From the beginning the hidden leaders of the uprising sought to avoid set-piece battles. The Oath Keepers and Halo Shields divided their forces to invade the worlds at the top of their priority list. But once the bombardments lifted from the sprawling fortresses, and the Adepts made planet-fall, it was clear that all static defences only boasted token resistance. Instead, the enemy had withrdrawn to mountains, jungles, swamps and subterranean mines. The conflict became a prolonged and bloody war of attrition, as the two Adeptus Astartes chapters learned to adapt their tactics. When a set battle was eventually forced upon the world of Purgatia, the Oath Keepers' highest ranking officers were met with a chilling surprise. Reconnaissance showed hundreds of traitor Guardsmen bearing great banners depicting the face of Luther. In truth, none of the Guardsmen had an inkling of the significance of this image. They had been ordered to paint and display it by the agents of one of the Fallen. Similarly, the majority of the Oath Keepers could not fathom this practice. But representatives of the Inner Cirlce were perturbed. Especially since Scouts from the Halo Shields had also reported this to their own commanders. A hasty decision was made. Veterans from the Oath Keepers boasted of their prowess to the Halo Shields, stating that they no longer needed their assistance. The Halo Shields were outraged. Many demanded an honour dual, but instead a decision was made to immediately withdraw all support from the campaign. The chapters parted company in disgust. Some among the lower ranking brothers of the Oath Keepers contemplated questioned the honourability of their veterans' conduct, but said nothing aloud.
The Fallen Angel was eventually captured when his last fortress was razed. This would be the first of only three members of the Fallen that the Oath Keepers would even capture despite their years of service.
In M34, the Halo Shields became one of the many chapters to be eradicated by the events of the Pale Wasting (see http://wh40k.lexican...ki/Pale_Wasting).
Edited by Welcheren, 23 January 2015 - 03:35 PM.