There is very little public knowledge about the slave trade, it is particularly in use by supernatural entities such as Vampires, Demons, Broxa, or other such non-human entities passing for human. The rules which govern this are somewhat arcane but very well documents, usually brokers and enforcers of this sort of ownership are Vampires, though not always. Some demons and even particularly powerful magic / psionic users have also set up shop in this trade. This does not mean that ordinary humans cannot own slaves, even in the modern world, but it is more rare than one would think. Supernatural creatures tend to have exceedingly long life spans which helps them to see humans as animals more than people, though there are notable exceptions in the upper echelons of high society around the world.
Household Slavery
This is one of the most common kinds of slavery, second only to sexualized slavery. There is also a good amount of overlap between the two types. A household slave will be entrusted to do domestic tasks, much like a butler or a maid might do. A household slave can be any form of domestic servant, usually going by titles from the Edwardian or Victorian eras. For most slaves of this type, the work is difficult and at times grueling but offers some protections over other kinds os slavery. Households slaves can become treasured possessions and treated with some amount of respect, especially in the highest levels of society and wealth. A household slave does have the ability to eventually become some senior type of domestic servant, managing a household for their owner and gaining some small amount of freedom and respect within their world.
Corporate Slavery
Corporate slaves are granted more freedom for certain purchases even to the extent that slaves are often used for anything including corporate positions of authority and no laws require disclosure of how many owned slaves operate in such positions. Certain types of companies will often have a number of slaves in the higher ranks that all, must report to and carry out the orders of their owners. These slaves have the most freedom of any others, often able to live on their own and have some semblance of social life outside of their work.
Sexual Slavery
Within the explicitly sexual slave trade, transactions typically run in back alleys and in the underside of the law where slaves are traded for drugs, money, guns, and even are used as a legal means to carry wealth into and out of the country. Among the rich slaves of this type are treated particularly poorly with little regard for anything other than their immediate or future use as devices of pleasure. Some slaves enjoy more comforts and are able to expand their duties to include more household functions becoming trainers of new slaves or managing the household slaves.
Slave Bloodlines / Breeding
Slave houses also exist where slaves are bread and produced for the high society with specific traits being bred often like prize dogs or horses might be. Blood lines valued and prized, specific attributes being bred for or bred out, etc.. There is some amount of regulation as a slave being purchased should not be suffering from PTSD or other sort of behavioral illness wether it is created by those holding the slave or by genetics. Slaves who might embarrass or otherwise upset a potential owner are deemed undesirable. Though there is almost always someone willing to buy nearly any slave when looking to appear as more wealthy than they are. Like cars, prize animals, and other such commodities having slaves can raise someone's social status within the right circles.
Owner Rights
All slaves must be documented all the way back to the original document where the slave gives up their freedom as a citizen and (supposedly) gives themselves into slavery. A parent can also sign their child over to slavery, though official a slave can ask to be set free and their owner is obligated to document and consider releasing the slave when they turn 18, they are under no obligation to actually release the slave. A successful release petition is more difficult to do than it sounds and requires the help of a kind of supernatural lawyer well versed in this arcane practice, meaning few slaves ever have the opportunity to do so. Another document is also usually obtained from young slaves during training which states that they give up that right and while the document is not supposed to be coerced it usually is. Documentation is key to the slave trade and key to proving ownership of a slave.
Theft / Escape
The continued slave trade has given rise to a particular type of supernatural bounty hunter. These hunters pride themselves on the brutal execution of anyone who steals a slave once a contract has been agreed to. The same hunters will also hunt down and return (or kill) escaped slaves. Thus, a slave cannot be stolen without mortal consequences. It is not uncommon for a thief stealing (liberating) a slave to be killed outright within days of making the attempt, even if the attempt succeeds. Owners can ask the supernatural leadership of a city or country for help in tracking down a prized slave and returning that slave to their care.
Slave Rights
It is certainly true that slaves do not have rights in most cases, they are property. In some cases, however, they can be transferred to another owner or even freed. Owners have a responsibility of care, a lack of care could bring the mundane world into the slave trade, which is generally agreed to be undesirable. A large amount of wealth and power are centered on the slave trade, thus slaves being grotesquely abused, neglected, or mistreated can be grounds for an owner to be stripped of their slaves. This usually does not mean the slaves will be freed, though in some rare cases it can. Slaves themselves do not have the right to ask for this, instead is must come from a free person. In most cases a free person petitions for the slave(s) to be transferred into their name.
It is generally accepted that one must keep their slaves in good / healthy condition in a broad sense. Slave owners are discouraged from mutilating / starving their slaves as the mundane world could quickly and unwittingly notice either occurrence and take action against it. Killing ones own slave is permitted so long as the mundane world is kept away from the death.
Marks of Ownership
While some owners choose to tattoo their slaves with a registered seal, far more common is a slave to be collared.
Brand
Mostly used by demons and similar creatures. A slave can be branded with a specially prepared and enchanted object. The owner must brand the slave themselves and once branded the slave is made susceptible to any command the owner gives. This kind of mark is particularly ancient and could be the very first instance of magic used for ensuring obedience in this way. Where the owner's commands are concerned the slave can almost seem like they are entranced or hypnotized, generally the command will override the will of the slave entirely. Many in non-demonic circles see this as particularly vulgar, a slave marked with a brand cannot be resold as the brand is permanent and non-transferrable.
Tattoo
These magical symbols are tied to a specific family line. The ink is magically enhanced and both provides a mark of ownership and a magical means of locating the slave. Once placed it cannot be removed, even if cut out of the slave it will reappear within days of the skin healing. The drawback here is that the mark will diminish the market value of the slave, as it cannot be replaced or removed. Slaves with multiple marks are not at all desirable and is seen as unseemly and unnecessary.
Collar & Fob
A collar and fob are a specific kind of jewelry. The slave collar can be any metallic, leather, or even synthetic kind of piece and is usually placed around the neck of the slave. The placement around the neck is customary but not required, placement around wrists, ankles, and even waists are also not uncommon. Unlike a tattoo the owner can choose to remove the collar when selling / transferring (or freeing) a slave. Most collars have some symbols which identify the specific owner / fob for which the slave / collar belong.
The fob is for the owner, it is a symbolic item uniquely / magically paired with the collar itself in a 1 to 1 ratio, for every collar there is a particular fob. The fob will have some symbols describing the specific slave / collar it is paired with. The enchantment on the collar and fob provide that the owner can use the fob to command the slave mystically to obey any command they are given with the fob. It is compulsory and a slave will have no choice but to execute the command even if that command is suicide.
Establishing Ownership
In any challenge to the ownership of a slave, paperwork is the most vital evidence to prove ownership. Without specific paperwork an owner risks being stripped of their ownership and their slave(s) set free. An owner can challenge the lack of paperwork and rely on their collar / fob to prove ownership if they have a compelling reason why the paperwork is impossible to produce. In rare cases if the paperwork cannot be produced a slave can be set free, most often the owner pays a fine of some kind to obtain paperwork stating they have paid for the slave in full.
Abandoned Slaves
An abandoned slave is a slave that goes unclaimed by the owner when the owner knows of the slaves location and is able to claim the slave. If a slave can prove their owner has not claimed them, they can be deemed abandoned. An abandoned slave can ask to be freed but more often than not they are sent to a slave house for future sale, if it is possible they will be returned to the slave house from which they originally came. Alternatively a slave can request to be given to a specific person who was not their original owner, this new owner can then accept (and pay for) the slave in question and take ownership. From there the slave can be freed by their new owner, though this is seldom what actually happens.
In some cases a slave can be deemed abandoned if they are owned by a person who dies without bequeathing the slave to someone else. This can also occur if they are owned by a family whose last living heir dies / denies to take ownership of the slave. Corporate slaves also can be deemed as abandoned under similar circumstances. By tradition slaves abandoned in this way are to be freed.
A slave can also be classified as abandoned if it is deemed that the owner can no longer care for the slave. This is rarely invoked and is the height of dishonor for an owner to be stripped of their slaves for this cause.