>What different models of slavery exist in your setting?
In terms of legal slavery, the most you would probably see is contracts drafted up to pay off debts through servitude, but even that's less likely to be full on slavery. Aside from that, you may see some trafficking of smaller or lesser races in major port cities, but that's more black market activity.
Demons also practice it extensively.
>In which nations would you find the largest portion of the population being enslaved?
Likely the one with the largest port focused heavily on trade, though again, that's more black market activity.
>What notable rebellions have been orchestrated by the common people?
I'm still working on the full history of the world, though so far rebellions seem like a less likely occurrence. One major one would have been on the isles to the east, being halflings and dwarves rising up against human colonists. Outside of that though, nobility tends to be those with magical bloodlines, so they've got a fair bit of claim to rule.
>What notable rebellions have been orchestrated by high ranking traitors?
Well, this is more ancient history, though long ago the gods killed the primoridal who spawned them. Then a member of the first race of elves rose to godhood and killed most of the other gods. The main god of the elves asked for help but they said no and left. So it was a really long chain of people being dicks. However, that elf did make the rest of the races and didn't exactly share a lot of this ancient history, so it's not very well known. Instead, he painted himself as a god of justice, law, oaths, light, and all that nice stuff.
Aside from that, any rebellions would have been infighting between nobles, most likely.
>Who are the most famous traitors?
This is a bit more twisting of history, though one of the gods who escaped that killing spree did so due to being a sneaky asshole. He's viewed by many as a scoundrel, and he's betrayed many