House Heraan, based on the planet of Heron Cove, is a relatively minor house compared to the more famous ones like Terryn, Hawkshroud, etc. They are extremely loyal to the Imperium and abide by a very strict warrior code. Warriors of House Heraan have to be capable fighters both inside and out of their Knight suits, because ritual honor duels between the pilots are very common, and often determine who gets the honor of becoming one of the Barons, or even the High King. Indeed, when the High King falls, usually a selection of Heraan's barons fight, sometimes to the death, for the honor of becoming the next High King. Thus, ranks and honors are not determined by bloodline at all, but by skill in combat. Other Noble Houses see this as barbaric, but Heraan's system ensures that only the very strongest and/or smartest get to lead them into battle. The downside is that many strong and capable warriors die in these ritual duels, or succumb to their injuries afterwards. The tradition of determining their leadership this way dates back to the early days of the Age of Technology, when the original colony ship crashed on the planet's surface. It was a struggle to survive the harsh environment of the planet (which was suffering from a severe Ice Age), and sacrifices had to be made due to food shortages, so this was one way that the weak were culled from the population. The planet has since been tamed and largely rendered safe in the millennia since, but the tradition of ritual combat for leadership has endured. The Imperium as a whole does frown on the somewhat barbaric practice, but the skill of the warriors of House Heraan speaks to the effectiveness of the practice.

As far as the heraldry goes, the main emblem of House Heraan is a heron, for which the planet itself is named. Indeed, the name Heraan is derived from heron. The herons found on the planet are far larger than any such birds found on old Earth, easily twice the height of a man. They were hardy enough to survive the harsh conditions of the ice age, and became revered by the colonists. When they gained the ability to construct Knight suits and the Knightly House was founded, they chose this bird to be their emblem. Other symbology includes the lightning bolts seen in many places on the Knights. They are simply a traditional symbol of power among the people of Heron Cove, and can be found on not only the Knights themselves but on the transport ships, buildings, and even tattooed on the skin of the House's warriors.

Warriors of House Heraan begin as initiates, where they learn basic fighting skills and tactical doctrine. Only the very brightest and most skilled will continue and have a chance to become Knights; the others will usually end up in the planet's PDF and potentially be called up to help defend their planet in the event of an invasion (which has happened before). The ones who do make it will get the chance to pilot an Armiger-class warsuit. As there are only so many of these machines, and even fewer of the larger Questoris and Dominus classes, few initiates ever make it this far, and those that do are the best of the best. The ones who show particular aptitude with Armigers are considered for advancement, and when a new Knight is recovered and repaired after its pilot is slain, these candidates will battle for the honor of taking the dead warrior's place. Some may die in the duel although it is actually fairly rare, but the winner will get to operate a Questoris Knight, becoming a true Noble. A similar system is used to determine advancement to become a Baron, if and when such a position becomes available.

There are three major Orders within House Heraan, and upon becoming an Initiate, a warrior is allowed to choose which he or she will join. They are largely traditional in nature, with different rituals and symbology, and some internal friendly rivalry between them, but no real difference in training or abilities. This order is denoted by a different shaped outline around each warrior's personal rune, which is tattooed on the warrior's right shoulder and, should they eventually gain the honor of piloting a Questoris or Dominus Knight, displayed on the right shoulder armor and left knee plate in a field of dark gray. The rune itself is chosen by the warrior, and is usually intended to reflect their personality in some way, although none outside House Heraan know the significance of these runes. The Order of Quicksilver uses a circular outline around the rune, while the Order of Steel uses a diamond shape and the Order of Obsidian uses an inverted triangle.

I'm sure I can come up with more fluff for this House later, but this is what I have for now. It's rough and unpolished, but I'm a modeller more than a storyteller.

The Household Guard of House Heraan

While House Heraan's main contribution to the Imperium is obviously the services of its Knights, it is unlike most other Knightly Houses in that it also contributes a number of regiments of Astra Militarum, usually alongside the Knights in various war zones. In point of fact, all of those who become Knights start their service to House Heraan as regular line infantry, advancing through the ranks until they are chosen to be trained as Knights and learn to operate the signature machines of the House. Only those who show extraordinary valor, combat prowess, and tactical ability will be chosen, and it is not only high ranking officers who are selected. The ones who make the selections are known as Choosers, and they function as Commissars in the army, even being trained by the Officio Prefectus to fulfill this function in addition to their duties choosing future Knight candidates. It is relatively rare for them to have to execute anyone for cowardice in Heraan's army, because the entire planet's population basically has a strong warrior ethos and culture, revolving around the military and Knightly House. Indeed, the deeds of the Knights are highly publicized among the population, leading to the Knights being revered as heroes. The fact that the Knights are not born into their roles, but rather earn them through deeds, only enhances this, as technically anyone could become a Knight if they are skilled enough and lucky enough to survive a few battles.