Gautgund

Background
The Marauding Eagles hail from the subarctic Feral World of Gautgund. This backwater planet was brought to Imperial Compliance by the Chapter itself at the very end of M34. The climate is harsh, with violent winds blowing most of the years, snow even at the hottest parts of the globe during bad summers and vast forest of oaks, larch and firs, dotted with villages whose population as regressed to early Iron Age levels of technology, save for the crafting of their armors, which shares a lot in common with primitives versions of the Space Marine's power armor.

All the humans inhabitant of Gautgund shares the same ancestry, which is proven by the fact that all the languages of the planet derive from an archaic form of Germanic dialect, which has evolved into thousands of forms. A Gauntgunder from a village may not even be able to understand the language of another leaving 50 kilometers away. Therefore, it is no surprise that warfare is quite common, even endemic, to the planet. The Gautgunder may have become a peaceful people had they had prevented their technological and scientific regression. or they could have had, at the very least, banded together if their world had had dangerous lifeforms hunting Mankind.

Instead, the Gautgunder kill each others for every scrap they can get their hands on, for women and horses and thousands of other fickle reasons.Even family inheritance is the source of much blood being drawn, with brothers killing brothers to be elected as heir to their father. Lacking any form of stability, the Gautgunder society may allow for the rise of a powerful kingdom during decades, only to reduce it to splintered fragments vying for power over one or two villages at the death of its founder.

It is this no surprising that the Marauding Eagles have proven to be quite savages and brutal, and sometimes lacking in the more spiritual traditions of Khan's Sons. However, the impermanence of all things is also quite ingrained into the Gautgunder's mindset and beliefs, hence their reverence for legendary figures and great heroes, whose legacy can traverse the centuries unblemished, standing forever over the squabbling of their heirs. The faith in the Emperor, while nominally present on Gautgund is far less prevalent than the worship of ancestors. In fact, even the prayers to the Emperor and Jaghataï Khan have had to be ingrained into the native's system of belief, with the former becoming the ancestor of all Humanity and the latter the Father of Warriors.

Fortress-Monastery
Arnwarin is the name of the massive Fortress-Monastery which houses the Marauding Eagles. It has been built upon a sole pillar of rock, a lonely mountain piercing the skies, surrounded by dark and deep forests. Long ago, before the coming of the Astartes, Arnwarin was the castle of a mighty lord of Gautgund. When the Eagle came, this warlord rejected their offer, refusing to surrender to the foreigner. The 200 Battle-Brothers then proceeded to obliterate his forces, killing or routing all his followers, driving them away from the smouldering ruins of this ancient castle.

Seeing the strategic value of this location, both thanks to its isolation and the natural durability of local stone, Alaric the Conqueror, leader of the Chapter, reached out to the Adeptus Mechanicus, petitioning for the creation of the Fortress-Monastery. During a decade, the Mechanicus toiled, carving great tunnels below the towering mountain and into it. At its top was created a space-port for the Chapter's fleet, a burning halo which is believed by the natives to be the gateway to their ancestor's realm.

Into Arnwarin, great halls and deep caverns are lit by torches and fire, each Brotherhood claiming for itself one of the peak's portion, from the very top for the Suntalons to the ground level for the Stormdaggers. Large passageways link those demesnes to the shared spaces such as the Training Grounds, Apothecarium and Archives of the Chapter. At the heart of the mountain lies the Hall of the Feasts, where the whole Chapter may gather to eat, drink and jest. In their fortified abode the Marauding Eagles may leave behind them their aggressive behavior, pursuing more fulfilling pursuits, such as reflection on the vacuity of existence, writing poetry or learning about their Chapter's past.

Surrounding Arnwarin is a deep and savage forest, where many a trap has been laid, laser-canons and mega-bolters hidden behind great rocks while servitors remains cloaked by vines, waiting for intruders to wander into their line of fire. Aspirants who aren't made Scouts yet patrol the forest, driving away any and all natives who would dare to explore it. After thousands of years of such practice, this forest has become a cursed place in the memory of the natives, who avoid it now, except for the most unconscious, arrogant or despaired people.

Recruitment
Unsurprisingly, the Marauding Eagles have a method of recruitment well suited for their brutal tastes. The Chaplains and Apothecaries from this Chapter eschew the use of elaborate tournaments or trials. Instead, they watch closely the constant wars of Gautgund, selecting those young warriors whose savagery and skills would make for fitting recruits. Those youths are then brought to Arnwarin, where they are tested for genetic purity and, if found satisfying, they receive the first seances of psycho-endoctrinement and the surgery which will one day make Astartes out of them.

While this method allows for a great influx of recruits, which is how the Marauding Eagles have been able to survive in the Halo Stars for so long, replenishing their forces enough to face off every threats, it also offer the Chapter with another advantage. Most of those Aspirants won't become full-fledged Scout Marines until 5 years after they have received the Black Carapace. While it is clearly a deviant practice compared to the wisdom penned in the Codex Astartes, the Marauding Eagles make use of it to bolster their gene-seed reserves without resorting to unfit bodies to replicate them at greater speed.

This practice has saved the Chapter several time during its past, allowing it to go from less than 100 Brothers to roughly 400 in less than twenty years, without a great loss of skill. For the Marauding Eagles, such practices are an absolute necessity to survive their constant war with the horrors infesting the Halo Stars.