The Dead Lands of Athas
A person can become a slave in one of three ways: by being born a slave, by being captured during a war or other armed conflict, or by being sold into slavery for committing some crime or failing to pay one’s debts. There are several classes of slave: gladiators, artists, soldiers, laborers, and farmers.
A member of any race or social class can become a slave, though nobles and merchants usually have friends or family who will buy their freedom for them. It is also rare for elemental clerics or mages to become slaves, as they can usually escape easily. Instead of selling such individuals into bondage, prudent templars simply execute them when they capture them.
We can take one bit of solace from the institution of slavery, however: there are a surprising number of former templars in their ranks. The losers of the political infighting in the king’s bureaucracy are often sold into slavery. Templar slaves are generally the subject of abuse and ridicule by their newly established peers and generally die quickly as a result of some tragic accident.
Unfortunately, slavery is such an ingrained feature of the Athasian economy that abolishing it completely would lead to poverty and suffering across socioeconomic lines.