Princeps - Princeps: A princeps (pl. princeps) is a senior officer of the Adeptus Mechanicus' Collegia Titanica who commands one of the towering Imperial or Chaos robotic combat walkers known as a Titan, and all of its crewmen -- moderati, Tech-priests and servitors -- are subordinate to them.Princeps are all people of exceptional willpower, which is required to enter a mind-link with a Titan and maintain their sanity intact amidst the roaring spirit of destruction housed within the Titan's adamantium hull.Although they belong to the separate military hierarchy of their Titan Legion and the Collegia Titanica, the princeps are still part of the Cult Mechanicus, and as such defer to the orders of powerful Adeptus Mechanicus magi, who command the might of the Titan Legions and are able to issue them direct orders and decide their assignments.The princeps exerts command over his war engine by the means of a Mind Impulse Unit -- a technologically complex neural input device which allows for a cybernetic connection between the Human mind and a Titan's Machine Spirit (artificial intelligence), and the ability to impose his or her will upon it.To establish the link between the Machine Spirit and the Human mind requires that the princeps submit to extensive cybernetic augmentation of his or her central nervous system, either by accepting the implantation of several cybernetic implants at the back of the neck and skull, a series of implants in the spine which enable the linking of the MIU to the spinal cord or even undergoing entombment in an amniotic tank with large parts of the body rewired to accommodate cybernetic interaction with the Titan.The process of linking the Human mind to a god-machine is very difficult and dangerous, as a Titan is possessed of a ferociously potent Machine Spirit; one that is unlike any other, harbouring its own savage and instinctive intelligence. The princeps must break the machine's opposition and bind it to their will -- a feat requiring enormous willpower.Because of this, princeps are rare individuals, and one of the tasks the Collegia Titanica carries out is to discover them wherever they can be found and train them to command the colossal war engines. Whilst normally the Adeptus Mechanicus searches for its personnel within the hierarchy of the Cult Mechanicus, the sheer rarity of such individuals requires the Mechanicus to search in the broader populace of the Imperium.Barely one in ten million meet the necessary criteria and neural profile to serve as a princeps, and even fewer of this number make it through the training to finally command a god-engine. Because of this reality, princeps are immensely valuable individuals, and their home Forge World will spare no effort to recover them should they go missing in action, and if the slimmest chance exists that they are still alive.There are two ways in which one can become a princeps -- undergoing training in Collegia Titanica academies, as mentioned above, or advancing from the rank of a moderatus to a full princepture, which is usually the command of a Warhound-class Scout Titan.When the princeps is linked to a Titan's MIU, they feel the Titan's body as if it was their own -- their hands become weapon arms, their senses are turned into powerful auspexes and their skin becomes the thick adamantium hull -- an experience of supremacy and escape from Human frailty that addicts every princeps to his or her link with a Titan.The princeps is then able to command the Titan intuitively -- they merely need to think of undertaking an action and the machine complies. During this operation, the princeps does not lose consciousness of his own body, and is able to simultaneously move and act as normal within the Titan's cockpit.