Origins

After receiving the precious geneseed and equipment from the Adeptus Mechanicus, the training cadre returned to a planet that was well known to their Commander, as the Storm Lords had found recruits there on several occasions. They claimed it as their own, and there they began to recruit and train new Marines as was their duty to the Imperium and the Emperor. After many years of building and training they earned the right to return to their beloved Chapter, their final duty was to turn over command to the new chapter's Master who christened them, the Stygian Angels.
Homeworld
The moon of Kirin, in orbit around the gas giant Maelon III, is the home of the Stygian Angels chapter. Though not technically a planet, Kirin is classified as a "city-planet" type Hive World. The great hive city covers a full 90 percent of the moon, with the remaining 10 percent a scorching wasteland. The Angels' Fortress Monastery lies in the middle of this wasteland.

Following the example of Jaghatai Khan's combining the warring tribes of the steppes of Mundus Planus, the Angels combine recruits from different gangs into a single fighting force. Their loyalties no longer to Kirin or its gangs, but now lie only with the Angels and the Emperor.
Beliefs
The Stygian Angels have a base belief that sets them apart from many of their fellow chapters. To complete the goal of the Emperor as the Angels interpret it, they will do anything. As the Angels see it, the Emperor's goal is to bring all of scattered remnants of mankind under the will of the Imperium, and to destroy all threats, those from within and without.
Anyone, or anything, that stands between them and that goal is to be destroyed. No amount of brutality inflicted or sacrifices made can keep them from pushing forward, and everything is justified in the name of the Emperor. In their eyes, the ends truly justifies the means.
We Are Brothers
Like the gangs from which their initiates are recruited, the Angels practice a unique form of brotherhood within the chapter. They set themselves apart from the rest of the Imperium, including other chapters of Space Marines. The don't see themselves as one among many, but as a single force tasked to with a near impossible goal.
Upon becoming Scouts for the chapter, each new initiate is given a bike of their own. Throughout their lives are marines, they will continually customize and personalize these bikes to reflect their own personalities. A marine's bike is second only to his bolter in value to the Angels that ride them.
Upon becoming full Battle Brothers, each new marine is reborn with a new name given by the chapter's elders. Their old names were a symbol of their old lives, and it no longer has a place within the new marine's heart. No matter who or what he was before, now he is a brother in the Stygian Angels, and he will live and die for his brothers. The names given represent the chapter's gang style of combat and life, names like the Skull Crusher and the Death Rider, and simpler names like Whitey and Bigfoot are common in the chapter.
Organization
The organization of the Stygian Angels reflects Kirin's gang structure. The chapter only recruits from their "city-planet" home. Only the best and most promising young warriors are chosen, with no regard for prior affiliations, to become Space Marines.
Recruits from different gangs, following the example set down by Jaghatai Khan, are mixed together in squads. Each squad become part of a Brotherhood, equivalent to a standard Company. Separate Brotherhoods are identified by their differing helmet colors.
Unlike other Codex Chapters, and even their parent chapter, the Stygian Angels are entirely a mounted force. They use Bike Squadrons and Land Speeders, reflecting their preferred style of warfare. The chapter is also completely devoid of Devastator Squads, replacing those slow heavy weapons squads with Attack Bike Squadrons instead. Fighting on foot is abhorrent to the chapter and Veterans do not use Tactical Dreadnought Armor, but remain in Veteran Bike Squadrons. Finally, they do not possess any Dreadnoughts, as those are seen as the epitome of slow "stand and fight" warfare that is completely opposed to the Angels combat style.
Combat Tactics
The Stygian Angels are a completely mobile force, specializing in savage urban warfare reflecting their gang-like lives. They make use of Bike Squadrons, Land Speeders, Storm Talons and other fast vehicles exclusively. Heavily armored forces are left behind as the Angels outmaneuver the enemy and attack them at their weakest points again and again.
Their vehicles allow the Angels to get in range to use their weapons quickly, withdrawal fast and reposition themselves quickly for another attack. Smaller forces are easily overrun by the Angels, while larger forces are confused as they are struck by mass attacks at different points repeatedly.
If an enemy goes to ground, taking up positions in terrain inhospitable to the chapter's mobile assaults, then the Angels use sustained orbital bombardments and air strikes to drive them into the open. Once in the open, the Angels' massed assaults tear through them with ease.
The Angels are merciless killers. Anything standing between them and the enemy is quickly destroyed. Their methods are nothing if not brutally efficient. It may seem cold hearted to others, but to the Angels it's all necessary to achieve the goals of the Emperor.
Prior to battle, squads are assigned to gangs. Each gang has its own hierarchy, its leader is responsible for for directing their attacks. If the leader falls, the next in command automatically takes over the attack. Squad members follow their leaders without question, and their complete lack of the need to communicate during battle confuses friend and foe alike.
Geneseed
The geneseed of the Emperor's 5th Legion, the White Scars, and their Primarch Jaghatai Khan was given to the Stygian Angels by their predecessors the Storm Lords. It remains pure and they remain loyal to the Imperium.
Edited by Ecritter, 25 May 2013 - 08:29 AM.