Slavery is a topic seen quite differently in various times and countries.
Slavery in Tortall
Slavery was common practice in Tortall. In the middle of the third century of the Human Era critical voices began to raise[1]. Due to the events of Bloodhound, it was banned in 249.
Slavery was already a problem for the Provost's Guard around 246 HE before it was forbidden as illegal slave auctions were held in the attempt of cheating the Crown out of their taxes. Furthermore the kidnapping of children for selling them as slaves was already prohibited[2]. In the Lower City of Corus the Market of Sorrows was a known place for slave trade.[3]
Slavery in other countries
Carthak still has slaves when Ozorne is its Emperor and doesn't seem to be inclined of giving it up.
The Copper Isles are also a slave-holding nation, after the luarin conquest many raka were slaves.