Slavery is officially outlawed throughout the entire Compact of Arvum and the practice has vanished for over a thousand years among every great house. Except, arguably, House Thrax. While the house argues ferociously that thralls are not in any way slaves, in truth the system of indentured servitude very closely resembles it. Criminals or prisoners of war on Thrax lands often lose their freedom and are pressed into service until they work off the debt created by their offense, and House Thrax claims nearly all thralls eventually regain their freedom. In practice, owners are free to assign ever increasing costs onto a thrall's debt, making freedom for many impossible.
Relatively few thralls ever leave the Saffron Chain to travel outside the reach of House Thrax's domain, and fewer still are brought to Arx. The reason for this is simple- if a thrall inside the city of Arx, it is extraordinarily unlikely that the owner's of the thrall's debt will ever see that thrall again. Even if they did find their escaped slave in-all-but-name, other houses and the crownsworn in particular are extremely unsympathetic to House Thrax's plight and typically grant the escaped thrall safe harbor, saying that while the thrall's debts still stand they are under no obligation to return to Thrax lands and effectively nullifying their enthralled status. For this reason, many of the thralls brought to the capital city of Arx are thralls that have significant family left at home that would face terrible punishments if they were to escape, or are individuals without the disposition to escape. A handful of those might be fond of their masters, but the majority are simply far too broken to contemplate it. Most of that lot stays in the Thrall's Lament, a series of small outdoor shacks that provide the barest of shelter until their masters have need of them.
Children of thralls are born free as vassals of the thrall's lord (or for commoner owners, their lord), though they may inherit their parents debts in the case of their thrall parents' deaths. Thralldom debts always have a monetary value, even in cases of prisoners of war, though the value of the debts and the arbitrary increases placed on those debts may be contested in a Thrax court, where the magistrates and lawyers (of a higher born social rank than the petitioners) are almost exclusive women, as is typical for Thraxian gender roles.