The Cohaagen Device was pioneered on Mars where a group of rogue cyberneticists and neurotechnicians decided they wanted to get into the business of dream dealing. It wasn't a new business, there was already a fair bit of the trade going on. There were black market peddlers who sold Sweet Dreams to people who wanted them, sometimes upping the ante with darker stuff. This was kiddie stuff, they argued, and that in the right hands they could do even better.
The Cohaagen Apparatus
The Cohaagen Apparatus is a SQUIDband turned up to 11, turbocharged, and then pumped full of jetfuel. The Apparatus, looks like a bizarre collection of wires, probes, neural scanners, and lots of shiny blinking chrome bits. It is approximately 45 kilograms in weight, and is typically attached to either an operating table, or a throne like chair. The person to use the apparatus sits or lays down while the machine is wrapped around their head. It is a frightening piece of machinery.
The tests were carried out on cadavers first, and it was demonstrated that the apparatus could 'suck' memories out of even a dead or damaged brain. Running these memories back through something like a dream feeder was jarring and deeply unpleasant. Eventually, the group, under the direction of it's leader, Cohaagen, decided to start working on living test subject. The memories extracted were much better and less incoherent. There was a side effect though, the 'donor' was left functionally lobotomized. Their memories weren't copied, they were torn out of their brains, leaving them in catatonic states, or in blank fugues. A few were left irreversibly insane, and a few just died.
The tap worked both ways though.Extracted memoried could be implanted in a person as well. This was discovered through what amounts to crimes against humanity human experimentation on the part of the group. They found that the memories extracted from the brain could in fact be copied from the data banks, even if it was one way for organic brains. They found they could remove the very identity from people, and place memories in other bodies. This was a great cause for hilarity among them, as they could put the persona of a man into a woman, a murderer in a child, a rapist in a woman, and so forth.
The Cohaagen device was found, and the men who created it were incarcerated. The details of the penal system 'losing' them is of no consequence to the details of the apparatus. The plans for the apparatus were disseminated, and they can be found, for the right price, and most of the technology required to build one is not horribly hard to come by.
Requirements to build:
Plan acquisition: hard
Technology skill: above average
Materials acquisition: hard
Programming: above average
Building a Cohaagen apparatus takes approximately three weeks, less time if it is done by a team instead of a single technician. Failures on the plan acquisition check is likely to alert authorities, as can checks on the materials acquisition that fail. The authorities are usually keen on keeping apparatuses out of circulation. A functional apparatus can command a hefty price on the black market
There is a market for programmed women. Women, and pretty men on occasion, will be grabbed off of the street or out of some slum where no one will notice their abduction. They are placed in the Cohaagen apparatus and their persona is 'sucked' out and saved. Other personas are then put into the body and sent back out to work. This is a very black market operation, and Dolls can be picked out by augscannen, or specific questioning. (The Voight-Kampff test works well)
Pocket Assassin - the Doll has a hunter killer persona planted in their head. The doll will attempt to reintegrate into society, lurching hard away from their old lives and towards their targets. Most pocket assassin dolls are programmed with the stolen persona of a murderer or serial killer modified with the desired target fixed as their fetish. Pocket assassins have additional engrams to resist questioning, and suicidal impulses after completing their missions.
Servitor - picked from among the most beautiful people, Servitors have their identity slaughtered and replaced with that of a meek seldom spoken servant. Servitors are popular among underworld bosses as they are trustworthy, and nearly silent, regardless of what is done to them. The Servitor is a masochist and submissive to the core, and through twisted engram manipulation, they enjoy perversely what is done to them.
Professional - The professional Doll has had a significant portion of their brain replaced with artificial components, this allows them to undergo more frequent brain draining and implantation. This also gives them the ability to use skillsoft chips, further enhancing their value as operatives, consorts, or servants.
There are times when there are people who simply know too much, but are too visible to just kill. A quick abduction and an hour on the table, and everything they knew is gone, backed up on a hard drive. The engram can be altered, reprogrammed, and then pumped back into the body. The person is generally 60% to 80% the person that they were, but close examination can show the damage done.
Reprogramming reduces the intelligence stat by 5% for every point below a perfect score on the test check. A failure leaves the subject a moron, anyone reduced to less than 50% of their original ability becomes an invalid, below 25% cannot take care of themselves. A critical failure results in a system shock check, failure on this means death, while success leaves the patient in a vegetative state.
Implanting a second persona increases the difficulty by one. Each time this is done, the difficulty increases by one. Part of this is a function of most apparati being built out of scavenged parts, and part is that there is only so much abuse a brain can take.
Replicators are also an underworld creation. Unlike identity and ego theft, the person being robbed literally has their mind tore out of their body. The stolen mind, the hijacked persona, can be downloaded over and over again into new bodies. The replicator differs from a Doll because the new bodies are either clones or robot shells. This leaves the people in charge with an endless ability to create tormented copies of a person. This can allow for petty things such as constantly resurrecting a hated person in a clone body so they can be tortured and killed over and over, or for more insidious things as filling a harem, creating a slave force of specialists, and so forth.
Kazinski was a well known and feared terrorist who vanished half a century ago. He offered his mind up to a group of anarchists, told them to download him out of his meat shell and make sure that he was able to continue his work down the line. When the authorities raided the lab, they found the terrorist dead, but in the decades since, he has returned a number of times to carry out terrorist attacks. Despite being killed six times, he returns periodically to carry out terror bombings, gas attacks, and arson attempts. Kazinski is a fear Replicator.
Replicators, or Dolls, and the rest are not a form of immortality. They are copies of minds, implanted in bodies. They do not carry the anima of a human being, there is no soul or other aspect. A replicator is a flawed copy, and carries out the most prominent aspects of their personalities. A murderer reborn has to murder, or they start to fall apart. The same goes for caregivers, prostitutes, junkies, etc. The worse the transfer, the worse the personality defects. Replicators seldom survive more than a few weeks or months. Dolls can live multiple lifetimes, but eventually the brain can't take any more abuse. Everything wears out.