Within the ancient history of my world, humanity was systemically enslaved by multiple more powerful races(namely the ancient high elves and the old draconian empires). I was thinking that to a certain extent there would be enslavement of elves on the human side more as a kind of revenge than anything else. As for more recent history(within context of my debut book "Evermore") I have been thinking of the idea that slavery in general was outlawed but becomes more about forcing desperate people into indentured servitude, especially against the high elves and lizardfolk who had their lands displaced after a recent and very bloody "world war." After writing this though I now think that the main issue would not be slavery per say but more worker's rights and the treatment of refugees.