Almost fair.
I have a 100% official contribution this time!
Some Imperial fluff mixed up in it, but it's linked quite closely to Eldar Knights so I left a lot of it in.
Knights (by Andy Chambers, excerpted from WD 126)
Knights are fast-moving powerful war machines, thirty to forty feet tall and controlled by a single warrior, that fight on the battlefields of the Horus Heresy in the service of both Eldar and Human armies. Recruited from feral worlds where lesser versions of these machines are used to herd mighty Megasaurs, Knights take to the field of war alongside other members of their noble families. With their devastating visor-mounted psychic and shock lances, the mere gaze of a Knight can bring death to its enemies.
THE BIRTH OF THE ELDAR KNIGHTS
Long before the Dark Age of Technology, numerous barren as planets were visited by Eldar seed ships. These inhospitable worlds were prepared for the long process of terraforming and then seeded with the essential ingredients to sustain of life. The Eldar plan was to create new worlds to colonize in thousands of years time. These worlds were known to the Eldar as Lilaethan or Maiden Worlds.
As their civilisation neared its collapse, a number of Eldar groups denounced the easy decadence offered by Chaos and abandoned the homeworlds in a series of migrations they called the Exodus, referring to themselves as Exodites. These groups travelled far away and colonized the Lilaethan, determined to escape the terrible fall of their a race that they had foreseen. On their arrival, the Exodites split into individual clans each led by a warrior elite.
Those who joined the Exodus came from all levels of Eldar society but were united in their determination and powerful will to survive. The Exodites were a group which had long been aware of the dangers of indulgence and hedonism; by choice, they selected worlds where their life would be hard so as to avoid the trap of sloth. To a great extent, this suppressed the natural Eldar character of intense emotion and intellect, and did indeed save them from the Fall. Among the Exodites, the intensity of the Eldar nature is expressed as a powerful loyalty to their individual clans and a strong determination to achieve their objectives.
The struggle for survival on these worlds was indeed grim. To enable them to deal with the harsh conditions, the Exodites converted the sleek war machines they had brought with them into tall walkers which they piloted across their new planets, tending the virgin worlds. The ruling warrior Elite gradually developed a system of status and honour which brought about the society now known as the Eldar Knights. Dwelling in tall keeps, the Knights strove to hasten the planets' evolution and bring life and order out of the primeval maelstrom.
After the Eldar Fall, the craftworlds sought out the colonists to offer them a place on board. The Exodites coldly told their craftworld brethren that they preferred to stay where life was simple if harsh, and the dangers were obvious. Though the craftworlds and Exodite colonies trade with one another, the Exodites still maintain that the easy lifestyle on the craftworlds is dangerously close to that which brought the downfall of their race.
In order to produce the food necessary to trade with the craftworlds, the oceans of the planets were seeded with algae to form vast floating weed beds. These weed beds and the lush vegetation of the primitive jungles provided nourishment for docile brontosaurus-like herd beasts called Megasaurs created by the Knights through cloning and genetic engineering. The Megasaurs in turn provided protein-rich food for the craftworlds. The herds were shepherded by the Knights in their machine-bodies, protecting the Megasaurs from predators and moving them from place to place to feed. On occasion, the Knights of different clans would clash over watering rights or border disputes, though combat took an almost ritualised form intended more to hone the Knights' skills than bring about bloodshed.
THE COMING OF MEN
During the Dark Age of Technology, scouts from Earth travelled far through the galaxy seeking planets to be used as agricultural worlds to provide food for the huge hiveworlds of Humanity. They copied the farming techniques used by the Eldar Knights already living on some of the worlds discovered. In a period referred to by the Exodites as The Coming of Men, the Eldar and Human colonists clashed in a series of bloody wars as the Eldar Knights sought to protect their homes from the interlopers.
When these planets were cut off in the Age of Strife, they became feral worlds. A warrior aristocracy grew up on the Human worlds, mimicking the lifestyle of the Eldar clans. On many worlds, the Eldar clans resurged to win back the lands they had lost and settled into a pattern of battling and raiding both against the Humans and each other. The wealth of the noble Human houses and Eldar clans was based on their herds and much herd-raiding went on. The herds were greatly reduced in size, but, as the only readily available food source, were just as important.
While the Eldar shared their duties equally throughout the clan, the Human nobility enforced a feudal system on those below them. A sub-class of Drovers looked after the herds, as the nobles would not soil their hands with such work. The Drovers' walkers were not, by law, armed with weapons even though they lived in constant danger from raiders and predators. This ensured that the Drovers had to rely on the Knights of the nobility for protection and nullified any chance of revolt.
As well as the nobles, each house could field large numbers of men at arms, either mounted on horses or on foot. These were equipped much like Planetary Defence Force and Imperial Guard units elsewhere in the Imperium, though with not nearly as many heavy weapons. When the nobles grew too old to carry on fighting in the harry and slash of raiding or the swirling melee of battle they would give their armour to their eldest son and take instead the armour of a Warden. Wardens formed the steadiest element within the noble houses, usually found defending the keep or protecting the Drovers.
On many of the worlds, groups of artificers and technicians became the most important of the nobles' subjects. They initially simply maintained the Knights for the nobles but soon learnt to speak with one voice, threatening to withdraw their services from any Lord who failed to take heed. They styled themselves as a priesthood for the half forgotten mysteries of technology and were called Sacristans. As their power grew, they arbitrated between the different houses to ensure they did not wipe one another out in bitter feuds. The ever-present dangers of their worlds meant the Knights could not survive wars of attrition and genocide, and this necessitated the use of chivalric values to settle disputes. Eventually the Sacristans on many worlds ritualised the virtues of Honour, Duty and Valour and passed on these traditions from generation to generation. With the acceptance of these values the nobles became known as The Chivalry.
In addition to the threat posed by hostile houses, the Chivalry had to fight constant battles against swift Carnosaurs which preyed upon the herds. Hunting the Carnosaurs honed their fighting skills to a deadly art, preparing them for the periods of violent warp activity which created monstrous mutated beasts. When such a beast was sighted, all the Chivalry would go on quests to seek out and destroy the creature before it tainted the land.
THE REDISCOVERY
Thousands of years later, the planets were brought back into the Imperium. When Rogue Trader Jeffers rediscovered the agriworlds he referred to their inhabitants as Knights, pointing out their many Knightly virtues as he emphasised the worlds' value to the Empire both as a massive food resource and as a source of born and bred warriors. The Administratum agreed with Jeffers' findings and quickly set about rediscovering the rest of the long-lost agriworlds. To their delight, they found that two in three of the originally settled worlds were still occupied by Humans working along very similar social lines. The remaining worlds were either occupied by both Eldar and Human Knights or held exclusively by clans of Eldar Knights with strong links to the craftworlds, trading natural raw materials for technology.
Often, a Knight world would be affiliated to a Titan forgeworld, producing food for it, while the Sacristans would come under the control of the Adeptus Mechanicus. Other Knight worlds were left with a large degree of autonomy, required only to produce food and obey the call to arms when given.