Science and Technology
Servitors and Tech-Thralls
Where Menials fail, Servitors serve to provide the Machine Cult with heavy labour and the additional computing power.
Servitors serve two practical uses, one they can perform activities where thinking, sentient, human would fail for various reasons, two they serve as an example for criminals that dare to breach the laws of the Machine Cult or the Imperium.
Servitorisation is a punishment considered preferable to death as it ensures that the body of a criminal will serve where its deviant mind would not. The process is complex and cruel, Servitors are sometimes referred to as 'lobotomized' (a barbaric practice of involuntary neurological mutilation) but that fails to appreciate the extent to which this punishment is enacted on the brain of the individual. Servitorisation is not about causing deliberately inflicted brain damage, far from it, the process 'preserves' the brain to act as the central intelligence for the cyborged machine it will later power. The brain is extensively implanted with bionic augments that trap it in cycles of pre-programmed behaviour unable to deviate from them without additional programming by a Tech Priest. This is important for while particularly stupid individuals might be condemned to an existence of menial servitude bright intelligent brains serve to become advanced calculators or the control mediums of vast machines.
From plodding labour-servitors, still relatively human in appearance, to the remnants of flesh encased in the controls of some baroque walking engine, Servitors fulfill many roles. This is because Servitors serve a vital duty to the Mechanicus and the Imperium, with the creation of machines capable of independent thought utterly forbidden the slave-minds of Servitors serve as vital 'processing units' where artificial intelligence might have once provided a way to enable machines to perform complex tasks independent of direct control and human oversight. In this way even those judged irretrievable in their first life may serve again.
Exactly how much of the sentience of the individual survives inside the mind of a Servitor is a question few Tech Priests have applied themselves to studying. And all for the better, for the unanswered possibility that something does survive the process serves as an all the more terrifying deterrent to criminals and rebels.
Not all Servitors are 'human' however, some are created from monsters grown in gene-vats, abhumans and even animals have their roles to play as Servitors.
Machine Spirits
It is a core tenet of the Cult Mechanicus that all machines are endowed by the Omnissiah with a Machine Spirit - the core or 'soul' of the device which must be placated with appropriate ritual behaviour in order for it to fulfil its sacred function. These rituals are shrouded in mystery and tradition, and can vary from something as simple as pressing a series of buttons while reciting a carefully-timed fragment of Binaric prayer to elaborate, cargo-cult rituals involving sacred unguents, incense and invocations of the Omnissiah.
Great Machines
The Machine Spirits of so-called Great Machines - immense, complex constructions like an Imperial Navy warship or a Titan - are nurtured and coaxed into life by the priests of the Cult Mechanicus. This is a delicate and sacred process which begins with the uploading of a living neural pattern: by ancient Machine Cult law, this must be taken from an animal. This neural pattern is embedded deep in the machine's systems, filaments growing through every control system and layer of code. Throughout the engine's lifetime it will learn and grow, becoming marked by the experiences and histories of the human crews which serve the mighty machine, and taking on some of their qualities and memories.
The Cult Mechanicus keeps banks and banks of genetic data and neural matter for this purpose. Various animal minds are approved and tested for various machine taskings: a freighter might use some sort of placid herd animal mind, easily roused to rapid action by threats but otherwise easy to guide and handle during long straights of inactive travel. A Warhound Titan, by contrast, will often use a predator's mind (often a pack hunter given warhounds are often deployed in squadrons), aiding the Princeps linked into it by giving them instincts humans otherwise lack.
The Mechanicus require only a tiny sample of neural material for the stability required to upload to a large machine's systems, meaning some extinct animals live on through these bizarre means.
This process can have its downsides, however. The strength of the primal mind of the Machine varies from forge to forge, from wild animal neural pattern to domesticated one; some Forges prefer to sheath the wild untamed neural pattern raw into the machine, whereas others tweak and lobotomise it until it is servile.
Regardless of local Forge habits, the sacred symbiosis of blending a human mind within a machine's manifold - the neural interface through a Mind Interface Unit or MIU required to pilot a Titan, and preferred by some Navy captains to steer their vessels - has an impact on the human component. The stereotype of freighter Captains being sedentary isn't entirely undeserved, for example, but it isn't entirely their fault either; the mind of the ship influences them just as they influence the ship. A Warhound Princeps might go a step further, displaying predatory body language, or even filing their teeth to points - such is the potency of an awakened Machine Spirit.
The Throne Mechanicum technology integrated into Imperial Knights is a rare exception to these processes, produced to STC patterns to allow a single pilot to operate these large mechanical fighting machines where in their God-Machine cousins of the Titans whole teams of Princeps and Moderati are required. The Throne Mechanicum typically possesses a default source program that dates back to the dark age of technology - embedded in it is a overarching drive to protect the worlds upon which the Knight is based - this infectious thought is something of an origin of how the noble protectors of the Knight Worlds such as Anaximund Alpha came to be and is a unique technology not fully understood by the Mechanicus.
Lesser Machine Spirits
Lesser Spirits, such as those found in laspistols, cogitators and other less awesome devices, are not born from living neural patterns. While the Mechanicus make no formal theological distinction between Machine Spirits, the 'Spirit' of an advanced weapon is more likely to be an ancient onboard computer, with a few characteristic quirks - or in some cases, something unique and supernatural. In most cases the techno-animism of the Machine Cult simply masks interaction with technology that possesses no animus of its own - though nobody educated enough to understand that a Tech Priest 'appeasing' the spirit of a Laspistol is simply sending instructions to the processor that governs its firing mechanisms and charge regulators would be stupid enough to say such a thing out loud for fear of persecution as a Heretek.
To this end the Imperium and Mechanicus apply a belief that all machines are possessed of this animus though they treat it as something to be respected it should be noted that both the Imperium and Mechanicus possess an innate fear of 'thinking' machines so rather than being responded to with joy, a machines 'machine spirit' answering back to the user is generally reacted to with horror followed by the destruction of the item as noted above, the fear of thinking machines is deeply engrained in Imperial and Mechanicus cultural history.