I also fleshed out the backstory behind the elven race a bit. They evolved on a world which had two races rather than one. Like other races, neither of their races was homogeneous; they were splintered and fractured. However, elves on that planet were akin to what a dog on earth would be if dogs had human intelligence and were capable of speaking the same way humans do.
In that they were subservient to the other race, and they had evolved to be that way; for both the other race and the elves, it was just a part of their life. Elves, in spite of being equals in intelligence, got pleasure out of serving their master race. And said race was rather technologically advanced.
Unfortunately, a disease emerged in the race, a super-bug: asymptomatic to the point where the only way to catch it was with intense medical examination, 95% lethality rate, incredibly easy to communicate, no existing vaccine, and no way to counter it. The only reason elves survived is because they were just biologically different enough to be immune to the disease, in that the disease did not cross the species barrier in order to infect elves.
While not every member of the race was wiped out, their population was reduced to the point where they became a dieing race: impossible to save, because they simply didn't have the numbers necessary to sustain a viable population. That, assuming that the survivors were willing to even bind together in the first place. To some extent, they did, but not enough, thanks to natural tendencies to distrust others for stupid (or even not so stupid) concerns.
Still, this did unite the elves pretty well. They did everything they could to help, until the last of their master race had died out. This had a way of unifying the elves, getting them close to being homogenized. They maintained their desires to please their masters, by keeping the memory of them alive and by continuing their work, which is why they inherited and continued to further the advanced tech. And in the modern day, they often apply the mantra of servitude to others as if they were their original masters.
However, while they have this tendency to want to serve, they are not pushovers. They can and have fought wars (which they won) in order to protect their way of life. So while they may be, technically speaking, a slave race in that they are often in servitude of others, this is not something that is inflicted upon them, and they are quite capable of defying expectations.
In particular, their definition of pleasing others may not match what would be typical, in that a thought along the lines of "the needs of the many" would apply, in that not serving one specific person but rather devoting oneself to the pursuit of, saaaaay, medicine to treat others as a doctor, would fit into their philosophy. So think less manual labor (and certainly less sex*), and more public servant on a grand scale, for what most of them see their lives as striving to be.
They do exist in positions you might think of a slave race as being in, but in a minority of their population, rather than the majority.
*For elves, except for pretty much the ones into BDSM (in that they prefer to be subs), they insist on having sex with an equal, not a superior. They are rather promiscuous and enjoy casual sex among peers more than most races do, but they would not have sex with masters; the few who do are the exceptions to the general rule. They do make exceptions in the case of formal courtship (as in, proper marriage between individuals) in that if one is of higher stature then it won't stop them from hooking up, but as far as sex outside of wedlock, it's almost exclusively between two on equal footing.