Because living tissue cycles material out and changes constantly, one of the only ways to place a permanent enchantment onto a person is to give them a tattoo, and then enchant the ink itself (or, vastly more complex and difficult but slightly more reliable, to enchant the pattern itself). The art of tattoo enchantment is fairly complex, and certain patterns have been shown to hold certain enchantments better than others.
Among the Nethar
Tattoos are fairly common among the Nethar and their slaves. Nethar will often sport intricate designs in their House colors, to curry favor with their Matriarchs. Slaves will usually bear black tattoos indicating ownership. It is a great shame for a Nethar to bear black ink, as it does not show up well on a pure-blooded Neth's skin and is the mark of a slave. The Nethar will also sometimes enchant their tattoos, to increase their own powers or to enforce obedience among their tattooed slaves.
It is possible to use biomancy to remove a tattoo. Other methods exist, but are generally less pleasant and leave terrible scars.