Elves

Mysterious and aloof, the elves of Kytheria constantly stymie the attempts of other races to determine anything about them. The majority live on the Rowan Islands, a chain in the southern part of the Shattered Sea, and all but one of their cities forbid non-elves from visiting (or leaving alive, should someone find them anyway). The largest cities in the world boast small elven conclaves, never numbering more than a few dozen, and even these elves keep their lives a closely guarded secret. In ten thousand years of Kytherian history, no one has seen an elven child, nor are human and dwarven scholars sure what religion (if any) or traditions or foods or anything that the elves possess.
What others do know is that elves are incredibly long lived, with some city-dwellers living for centuries and often living within a city for its entire lifetime. Their language is incredibly sophisticated and complex; humans and dwarves learn a pidgin version if they wish to make trades or honor elven friends, but the levels of inflection and nuance possible by an elf speaking her native tongue for three hundred years simoply can't be paralleled. This long life also gives elves no excuse not to practice numerous skills, and even the most humble elf is capable of fighting with at least one weapon and speaks at least two other languages. The man'di have a strange relationship with the elves, and dwarven historians have noted several occasions on which man'di armies appeared lead by elven generals. While dwarves are the exclusive creators of some of the more fantastic materials in the world, elves have a monopoly over godstone and amber, a curious substance that no one else has ever been able to find. Elves also appear in wild places on occasion, serving as cryptic guides for mortals with heroic destinies.
A small handful of sages have pitched the radical idea that elves are not born, but created from the souls of heroic mortals. These proto-gods are ancestors given form to pursue that which only ascended ancestors may, and that pursuit is likely not something that a mere mortal would understand. Certainly elves have demonstrated close to god-like powers on occasion, and gods have appeared in Kytheria. The lines are blurred, perhaps deliberately.
One last thing to note is that elves can and do have children with mortals. The results vary, but their progeny tend to be extremely charismatic and blessed with health and longer life than most.