Astoth Knight Army
Aside from the Tempest Angels Chapter, the world of Astoth is protected by its local force of Knights clad in powered adamantium exo-armour provided by the Adeptus Mechanicus for millenia- since Astoth was settled as a Knight World during the Age of Technology. These Knights follow the principles of the Terran knights of old and have vowed to protect the Astothian people for uncountable generations. These chivalric Knights have made war a ritualized art, techniques passed down from forefathers to be honed and improved by Knights further down the line. Each Knight belongs to a noble household of Astoth with their own proud heraldry to display on their armour. These Knights have fought alongside the Tempest Angels to defend their home against Tyranids and Chaos Space Marines alike, showing no hesitation in standing shoulder to shoulder with their guardian angels of death.
In times where Astoth isn't under attack, these Knights test their skills at arms in tournaments and keep a watchful eye over their ancestral household's lands for predators and bandits that prowl looking for weak prey- prey that these Knights dedicate their lives to protect. They number in the low hundreds but in combination with the Tempest Angels, it has certainly proven enough in the past. Whilst primarily acting as protectors of Astoth; the Knights campaign off-world to fight the many threats the Imperium faces- especially when they are requested to do so by the Imperium. Indeed, it is not uncommon for them to launch crusades alongside the Tempest Angels to reclaim lost worlds.
Knights normally deploy in squadrons comprised of several of these war machines. These ancient battlesuits stand thirty to forty feet tall, are protected by nearly impenetrable Ion Shields and armed with a devastating array of heavy weapons. Imperial Knights are colossal war machines that tower over the battlefield. They are propelled into battle by powerful servos and have the power to kick over tanks and crush soldiers into red paste. Vulnerable limbs and joints are protected by sweeping armour plates of adamantium and supported by an incorporated Ion Shield which responds to the thought-commands of its noble pilot. The presence of just one of these towering engines of destruction is enough to change the course of a battle- even against foes such as demons of the Warp.
A Knight's Machine Spirit is of a particularly unusual type: to interface with the suit, an aspiring noble must first join with the Throne Mechanicum (the Knight's control system) in a ritual known as the Rite of Becoming. Due to a quirk in the bonding process, the device retains an imprint of each of its former pilots' personalities at the time they were first bonded, and as a result individual suits may develop traits echoing those of their former masters. The link also affects the noble's own mind as well; exposure to the metaphorical (or possibly literal, since there's been at least one case where a Throne Mechanicum took over operating the Knight when its noble was slain by using the memories of its old operators) ghosts in the machine inevitably causes the noble to develop strong positive feelings towards the concepts of fealty and hierarchy.
House Aglorion: The largest House on Astoth also happens to be the oldest. They have fought alongside the Tempest Angels as stalwart allies since they arrived. They have a stronghold simply named Aglorion Keep in the northern mountains a fair few kilometers away from Omnis Fortis which- apart from the Fortress Monastery itself- is the most defensible position on the planet. They boast approximately 160 Knights. Some of which accompany the Tempest Angels on their campaigns.
House Reinhold: This House is known for rarely being on Astoth- they spend the majority of their time crusading on foreign worlds for the glory of the Imperium. Their stronghold lies in some thick forestry of Astoth and is filled with a plethora of trophies from various campaigns. They are the second largest and have approximately 120 Knights.
House Elyas: Unlike the other Houses, Elyas mans two strongholds; one lying on the equator of Astoth and the other on the nearby agri-world of Oscion. They have the responsibility of protecting the important planet from invaders in order to keep the food supplies running. They field approximately 80 Knights- 60 of which are on Oscion.
House Americ: In the past, House Americ were one of the larger households, but recently suffered crippling losses that would have otherwise rendered a House all but disbanded were it not for their close relationship with Layria and the Mechanicum there- who have resupplied them with enough knight armours to bring them up to approximately 60 from their previous 6. They are always the first to arrive to support the Adeptus Mechanicus in times of need. Their keep lies just north of the equator.
House Arnet: The smallest and humblest of the Houses, their small keep lies just south of the equator. They fully dedicate all of their 20 knights towards the aid and protection of the local Astothians.