In 40K, each Knight Household will have dedicated Sacristans, trained and indoctrinated by the Adeptus Mechanicus to large amounts of failure because it turns out that the Sacristans have a deeper loyalty to their Knight House than the dreary cogs of the Mechanicus. At least according to Knights of the Imperium by Graham McNeill anyway. In 30K, the Knight Households still have Sacristans to repair and maintain their suits for them, and also Forge Worlds to build them. They are actually trained by an Archmagos Prelate. Awesome. This holds true especially for the Knight Households that remain in contact with far-flung Forge Worlds, and they develop symbiotic relationships. Basically, you protect me, I fix your awesome suit for you.
Those who swear fealty to the Mechanicum are often rewarded with esoteric augmetics, and have much improved suits such as the Cerastus Knight Atropos. Pretty good deal, if you ask me. One of these oaths is known as the Sidon Protocols, because one of the writers read the cool mecha manga Knights of Sidonia. Anyway, the Sidon Protocols is a complex web of obligation and duty that binds both House and Forge in a dangerous accord where failure to uphold the protocols leads to the Forge robbing the Knight Household of its independence and autonomy. In return? All they get is the right to wear the Opus Machina...dude, the Aquila looks cooler. Join the Emperor's side if all you want is a cool crest.
|Back in our time, Knights look like this...|
Thankfully, most Imperial Knight Houses remained loyal to the Imperium despite the events of the Horus Heresy, as well as the betrayal of the Fabricator-General of Mars, who decided to side with the warmaster. Following the example of House Taranis, most Knight Households kept their oaths to the Imperium and wrought heavy destruction upon the Traitors. After the Siege of Terra and during the Scouring, the Loyalist Knights sought out and almost completely destroyed every single Knight House that had turned Traitor. Awesome. House Devine, the Traitor Knights in Vengeful Spirit, were driven back to hiding in the Warp after House Terryn and a bunch of Loyalist Houses set upon them with destructive vengeance. Serve them right.
Knights of the Imperium! We march!