Through the Dragon
Although Fallow and Estor have completely outlawed slavery (with the possible exception of Kobolds, see below) not all of the world is so liberty minded. The Orclands are still a bastion for the practice, most tribes and larger organizations taking prisoners from other tribes and the local human colonies as slaves. Many human colonies are not above doing the same in return, taking races they consider sub-human (mostly orcs) as slaves or indentured servants.
Orc tribes are also known to capture ogres and trolls and use them for heavy lifting and/or combat, but it is unclear whether they consider them slaves or more as pets.
The Question of Kobolds
It is unclear whether Kobold tribal worship constitutes slavery. If so, the Empire of the Dragon Monarch is in fact the largest slave owner in the world. This would also mean that slavery is not outlawed in Fallow or Estor, as every attempt to mandate a fair wage for Kobold work has been met with miserable failure.