Most of the civilized nations of the world despise slavery because of the savage enslavement of Cirinnia by the Cyclopes. Most of the nations of man were founded by rebel slaves. The Drow are the perverted creations of Elven slaves and Duergar were likewise crafted by the slave pits of the Cyclopes.
The ancient human empire of Pelias never suffered under the yolk of the Cyclopes but basked in their own glory. Once the doom came to their empire the refugees came to Cirinnia to rebuild their mighty empire. Most of those that did survive were soldiers, nobles, and artisans; leaving them with a miniscule labor force. The humans of Pelias were unable to bring themselves to enslave their fellow humans, nor were they willing to risk the wrath of the anti-salvery human kingdoms. So Pelias began to enslave only non-humans. It began with orcs and goblins but soon dwarves and elves were rounded up and enslaved on the flimsiest of pretenses. To this day Pelias is built on the backs of non-human slaves who prop up the opulent lifestyle of the empire.
The Janni see all intelligent races of the material plane as their chattel and respect only those extraplanar beings that are more powerful than them. The Janni prefer more intelligent slaves like humans, elves, dwarves, and halflings. Monster races tend to be rebellious or too stupid to follow orders. Most of their slaves are the planetouched, which were created by the interbreeding of Janni with humans. The civilized world despises slavery so most Janni slaves are traded from Gnoll horde lords or the Hobgoblin Khanate until recently.
At the end of the last war the King of Reynes was deposed by the leader of the Raven’s Sons mercenary company. One of the many changes made by it’s leader Adar Ravenstor was the institution of human slavery as punishment for crimes and for gladiatorial combat. Since then Reynes has gotten rich selling human slaves to the Janni and non-human gladiators to the Pelisians. Their neighbours despise this and constantly bicker over prison sentences of their subjects and claims of slavers conducting raids on civilians. A century of war has left Reynes’ neighbors unwilling to go to war but tensions are rising.