"Ah... there had been plenty of cases of unicorn slavery, if that's what you were asking. Though, keeping them happy through cooperation is relatively simple? Or at least simpler than the alternative."
"Faen's powers are either life-related powers or companion powers. They can create companions of other species, the only ones that can do so. Thus, their society already have a place for other beings. It's just that that place is strictly below the Faen themselves."
"The ruling varies per species. And well, it also varies per territory. Faen's nobles usually have command over the laws of their respective territories, though mistreating non-humans is never a good idea for stability. I think humans had a similar model, but with humans on top - their empire is entirely gone and obliterated - and much fewer members of the other species around. Giants do have a nobility, but do a lot of voting and officializing laws in written format - it fits our outlook of learning and improving."