Servitors come up in the fiction all of the time:
• floating servo skulls;
• the creepy floating cherubs;
• the a varieties of servitors: former human pseduo-undead merged with technology slaved for a specialized task (singing, doing some navigation thing, being a murder servitor)
• who ends up being servitors. I was hoping it was mind-wiped real criminals, but I have a bad feeling that it's not;
• why do they need servitors? is there something about the biological parts, particularly the brain, that is necessary;
• they seem to be able to persist for some time. Are they "undead"? Are they cyborgs?
Thank you in advance for your assistance.
Many people have already answered but as my own reply went missing in cyberspace, I'll give it a retry.
There is a lot of (often contradictory) information floating around but in general there seems to be 4 broad categories of supply:
Criminals. These are humans who have run afoul of Imperial authorities. Either because they purposely broke the law or because they failed their duties. Imperial Armour Volume XI describes an Inquisitor-Lord who fails and is sentenced to millenia of service as a servitor for his crimes….
Honored humans who after death provide skulls to be used as servo-skulls. Often these are servants who are given the opportunity to continue to serve their masters after death.
Vat grown 'humans'.
Unwilling humans. When the cog-boys need servitors, they are not picky about whom they impress in their service. Humans from forge worlds, human tithe to be processed or even human pilgrims who made the fatal error of landing on a forge world/tech-priest ruled world…Basically whoever they can get their hands/appendages on and who is too weak to scare them.
As to the reason of their existance, that seems to lie in the past. Humanity mastered AI technology and created robots to serve their needs, both worker types and combat types. These eventually rebelled after which AI is forbidden and all robots must have some kind of human/animal brain processing power. It is not necessary to provide processing power to servitors/robots but their presence and usage seems to prevent autonomous behaviour as well as possession by deamons.
AFAIK, there is no strict canon regarding their maintenance requirements. Most sources and forum threads seem to indicate they do require some kind of maintenance (either plug in power and/or food paste) but published adventures indicate they can survive quite long without it although suffering from some degradation.
Hopes this helps.