|The Nilfgaardians needed more workers ... There were about four hundred prisoners at work here in Riedbrune. A good five hundred worked in the mines and surface mines ... and over a thousand built bridges and a smooth road through the Theodula Pass.|
|- The Tower of the Swallow|
Slavery is the practice of owning people like property in which the only one who benefits from such a relationship is the "owner" as a "slave" tends to have no real rights and doesn't need to be compensated for any work they do.
Slavery in different cultures
Unlike in the Northern Kingdoms, slavery is widely practiced in Nilfgaard, where prisoners of wars or criminals are used not only for manual works but are even allocated in the army, fighting as a vanguard before the "real" army's attack.
During the second Northern war, Nilfgaard invaded the kingdoms of Aedirn and Lyria; the capital city of Vengerberg, was conquered after a week of siege. Most of the population was butchered while the ones trying to escape towards Redania and Temeria were captured and enslaved by the Nilfgaardian cavalry. Slaves were in fact the cheapest workers for Nilfgaard. Riedbrune was one of the main slave sites under Nilfgaardian control. Prisoners of War from Lyria, Aedirn, Sodden, Brugge, Angren, and Temeria were forced to mine the stone caves in order to build a fortress. In the capital and in the other settlements of Nilfgaard many slaves were trained in special schools in order to become gladiators. By 1272, slavery was still allowed in Nilfgaard and its provinces, like Vicovaro.
During the Third Northern War Skelligers started capturing Nilfgaardian prisoners and using them as slaves. It wasn't however much rare to see slavery applied even on Skelligers: whenever the clans of the islands clashed or assaulted a village, the inhabitants were captured and enslaved.
Humans are not the only race to use slavery in their society. The elves, in particular the Aen Elle, used the human inhabitants of the realms they conquered as their servants. Skellige is one of Eredin's favorite hunting grounds for new slaves. The isles' warriors are fierce and hearthy, perfect for physical labor on Tir ná Lia. But that is not the only reason. The King of the Wild Hunt draws sadistic pleasure from breaking these proud men and women.
- According to Dainty Biberveldt, the citizens of Novigrad that were unable to pay their debts or the taxes, were imprisoned and forced to work in the mines, but they were not called slaves.