Knight Worlds - The Forge Worlds: Most knightly houses, though by no means all, are associated with a Forge World, and in return for fighting alongside that Forge World's Titan Legions, they gain access to advanced technology and knowledge that only the Adeptus Mechanicus possess.The association between the knightly houses and the Adeptus Mechanicus dates back to the time of the Great Crusade. When the Knight Worlds were first discovered, the different Imperial organisations that made up the Great Crusade competed ferociously with each other to gain control of the valuable resource the Knights represented. This Machiavellian political contest went on for solar decades, until the ancient Mechanicum of Mars was finally able to establish their dominance in the right to exploit the Knight Worlds.The Mechanicum were driven in this by a desire to gain control of the archeotech that could be found in abundance on the ancient Knight Worlds, but were also aware that the vast natural resources and military might of the knightly houses could make them a valuable asset in the service of the Machine God. To this end, once they had established their right to exploit the Knight Worlds, they set about making them dependent upon the Mechanicum for their continued survival.At the time of the Great Crusade, the Tech-priests' space fleets found an anarchic galaxy where the ancient confederacy of interdependent Human-settled planets no longer existed. The surviving Knight Worlds that were discovered had not retained all of their old technology and had devolved into feudal states ruled by aristocrats. The Tech-priests settled amongst these feudal empires, founding many Forge Worlds, and established contacts with the knightly houses, trading with their worlds and investigating the ancient ruins where surviving technology could still sometimes be found. The ferocious warrior Knights proved invaluable in combating enemies such as marauding Orks and land-hungry Aeldari Exodites.In return, the Tech-priests promised technical expertise and helped the Nobles to rebuild their planets to the Imperial standard of technology. The most important thing that the Tech-priests brought to the Knight Worlds was the knowledge and technology needed to maintain the Nobles' suits of battle armour.Over the course of the Age of Strife, much of the expertise needed to keep the complex suits of Knight armour working had been lost. Local technicians and artificers did their best to maintain the suits, but in many cases, they simply did not have the necessary technical ability.When the Knight Worlds were rediscovered, most had only a handful of operational Knight suits remaining, and even these were in a poor state of repair. The Mechanicum promised to remedy this situation by inducting the local technicians that had been caring for the armour into the Cult Mechanicus, teaching them the skills they needed to keep the Knight armour in good repair. Because of this, nearly all suits of Knight armour now bear the mark of the Cult Mechanicus as a reminder of the debt of gratitude they owe to Mars.Over the millennia, the Forge Worlds have grown powerful, with the Knight Worlds flourishing alongside them. Year-long, the Knights battle and patrol until the great cargo ships arrive from a Forge World, bringing new Knight suits, weapons, tools and mining machinery. They leave with their holds packed with ores and food.The Tech-priests and the Knights are now mutually dependent, and many Forge Worlds form the hub of a tiny empire consisting of a Forge World and its surrounding Knight Worlds. In return, the Knights have gained much from the Tech-priests, their worlds gradually returning to being technically sophisticated cultures. However, the relationship between Forge World and Knight World is not always an easy one, and nowhere is this more true than in the fraught relationship between the Knights and the Sacristans trained by the Adeptus Mechanicus to maintain their armour.