Firstly, there is the obvious disclaimer that slavery is merely a feature of setting in the imaginary universe of AIF. It is meant only to serve as a means for making the settings unpleasant and dramatic, and in no way should be construed as any sort of endorsement of slavery. Slavery is officially regarded as "a bad thing" by the creators of AIF, just like many of the other "bad things" stuffed into this imaginary realm in order to make it interesting in the manner of a Chinese curse.
The history of slavery in AIF is a confusing mash of various traditions, ranging from horribly exploitive practices to the keeping of intelligent pets. There are many societies wherein slavery is illegal, and they have their own means of enforcing their local laws. For the rest of the AIF universe, especially where there are no laws, slavery is mostly about the relationship between master and slave.
For biological beings, nothing is as influential on the nature of the master-slave dynamic as the presence of the infamous "slave juice". Slave juice is actually a replacement or superposition of the nanoscopic robots that normally exist in virtually every AIF being. The slave juice use the neural connectivity function of the nanoscopic robots to affect the brain functioning. The slave juice cannot establish itself if the subject does not permit it, but that only really matters if the subject is accidentally subjected to a dose of slave juice. Typically, the subject is only in a situation where they are faced with possibly becoming a slave when they are dealing with a party capable of persuading them (for whatever reason). Additionally, a being can be killed and have their body reanimated (with the usual medical equipment - med kit, med pack, patches), where their mind will essentially be vegetative and is wide open for the slave juice. Typically such beings have no useful remnants of their previous selves, though the nanoscopic robots can preserve some memories despite temporary brain death.
The end result of "slavamization" can be quite varied. The basic function that dictates the amount of effect is the degree of control that the slave juice is set up to do. This degree of slavamization is fixed at the time of the application of slave juice. Simply put, the more control the slave juice has, the more impaired the slave's cognitive functions are.
The most heavily slavamized beings, usually including those killed and re-animated, are reduced to being only semi-sentient (intelligence = 0), and a loss of previously earned abilities (skill = 0, occupations lost). Note that none of these attributes can go any lower, no matter how liberally the slave juice is applied. These entities have very little intrinsic value as they cannot meaningfully interact and can follow only the most basic commands, often unable to even distinguish who they should be listening to and consequently obey everyone or no one. They primarily exist as mistakes or as a means to desecrate a body.
For less extreme slavamization, the degree is measured by the size of willpower threshold between the master(s) and the slave. Once given a command by their master(s), a slave must obey it unless they attempt to disobey. An attempt to disobey is checked by having the slave roll 2 D6 and adding to their willpower (or, what remains of it), then comparing it to the command's power. The power of the command is established at the time the command is given, and is the master's willpower, plus 2D6, plus the slavamization willpower threshold. Every attempt to disobey is very unpleasant, even painful for the slave, and requires a consciousness check at some point (to be determined by the referee). A successful attempt to disobey is only useful for one instance or act of defiance. Failing an attempt to disobey by a significant margin they may cause them to sustain stress points.
The trade off is that every point of willpower threshold requires cumulative sacrifice of Intelligence and Stage (distribution to be chosen by the slave). So, the more control there is over a slave, the less useful they will be.
It is possible to slavamize a being using a zero threshold, thus maintaining their maximum usefulness, however these slaves have the greatest risk of to trying to kill their masters. For this very reason, most large slaving organizations sell slaves that have already been instilled with commands delivered by beings with fearsome willpower to protect the owner(s). Nevertheless, double-sixes still count as automatic success in an attempt to disobey, and so a lucky slave can still sometimes manage to attack their master(s). What's more, commands that are older than a few years (exact timing at ref's discretion), tend to lose effectiveness if there are too many of them or if they are too complex. So slaves are usually only left with a single, simple command to not harm their masters so that it does not fade with time. Other important or elaborate commands need to be regularly reinforced.
The effects of slave juice are usually permanent. However, if a master releases a slave from service as a specific final command, the controlling elements of the slave juice can be deactivated. If this happens, any intelligence lost from the slavamization can be repaired by a biologist of stage equal to the number of points of intelligence lost. The skill lost from slavamization is not recoverable.