Goblin-Sylph Hybrids

To the sylphs of Sadrom, very little is more terrifying than the prospect of being captured by goblins. They are known cannibals, having been widely documented as eating other sentient races even when other food is available, and it is said they have a particular taste for sylphs. Even those individuals who are "lucky" enough to be captured and tortured for information are thought to be doomed, as goblins take great pleasure in permanently crippling their political captives before they might, on occasion, trade them back or release them. Given the most prominent Sadromi outlook on able-bodiedness, this is just as much a death sentence as being eaten alive.
However, truly horrible tales are passed around regarding what goblins might do with female captives. Some stories speculate that packs of males may hold female sylphs hostage, mating with them to produce horridly warped and twisted hybrids that live beneath the earth and fly through huge cave systems on bat-like wings. For a proud race that considers goblins to be little better than violent animals, this prospect is enough to chill the blood of even adult sylphs. Such myths are usually considered to extreme to tell to children.
In truth, there is a subspecies of sylph that lives below the earth -- known to themselves the throan, they are a result of magical experimentation during wartime, rather than being hybrid crosses between one race and another. They are born as sylphs, but go through a cocooning process that alters their biology to allow them to see in the dark, grow claws and teeth much like goblins do, and alters their wings to a membranous rather than feathered state. They hate goblins only marginally more than the sylphs who originally rejected them... and they do, indeed, sometimes take prisoners from among the sylphs to supplement their breeding population.