One cannot accurately call the people of the World superstitious. They are mistaken about a great many things, but one cannot truly be superstitious in a world where ghosts arise to torment their murders, strange creatures -- half-beast and half-man -- make their home in the darkest woods, and magicians weave spells to prolong their sinful existence. Peasants have good reason to leave sprigs of wolfsbane above their door and to cross themselves when passing over certain bridges. This is not to say that the folk of the World know exactly how, why, or if these practices are effective, but they provide a modicum of hope in a land filled with horrible creatures and diabolic cults.
Not all things can be stopped by such ritual. Woe be unto the woman who gives birth on a pagan festival day, for they are doomed to raise a Changeling. Pagans say that the Old Gods punish the spirit of the child for having the audacity to distract from the rites which are owed to the gods. Followers of Law say that the sinful acts of the pagans on such feast days allow demons or fairies to enter the Material Plane and steal the child in order that they might replace it with the Changeling. Countless other explanations exist. Perhaps it has nothing to do with the feast days. Many a bard's tale tells of ghostly lovers or strange dreams causing the creation of such beings. Hunters sometimes return from the woods "changed" as well.
Changelings are strange beings. They seem to grow more quickly than normal children, but they retain their youthful appearance well into their ninetieth year. Those who changed when they were adults are often experts at skills they showed no affinity for in their previous lives. All a masters of magic, and the arcane arts seem to come naturally to them. They are equally skilled with swords, bows, and other weapons of war. According to the stories women tell to each other while they prepare their husbands' freshly killed game, Changelings often use these powers to bewitch their parents or lovers. The endings vary, but all are too horrible to relate to those of us who live comfortable lives outside the toil of Premodern life.
Like the other creatures of the World, Changelings exist outside of the tales of hunters and old women. All bear some strange feature or mark of their nature. The nature of their mark varies wildly. Some bear strangely curved horns, others unnaturally colored eyes, and still others seem perpetually covered in soot and grime. These sorrowful beings wonder the World, for no sane person would ever let such a creature into their home. However, despite their appearance, Changelings have very human minds. They feel sorrow and pride and mirth as much as any other human. Perhaps woe is not visited upon the mother, but upon the Changeling itself.
Despite the seemingly innumerable ways Changelings can occur, they are extremely rare. Most will go there entire lives without seeing one, or indeed without hearing a story about one that had any basis in truth. Perhaps this is the reason they are shunned.
I strongly considered removing the Elf entirely from the Nightwick Campaign world -- well, as a player option anyway. Some suggestions here led me to consider this option. I must say that I'm rather happy that I found a way to contextualize Elves. I'm not always a big fan of their psuedo-Tolkien flavor, but I rather like the idea of a Fighter/Magic-User hybrid. This model should allow me to keep that as a player option while still making Elves mysterious and frightening.
I'm not entirely sold on this option yet. I'm worried it might be a bit too "emo," but such is life.