Elves

As with fairies, elves eventually developed a reputation for pranks and mischief, and strange daily occurrences were often attributed to them. For example, when the hair on a person or horse became tangled and knotted, such "elf locks" were blamed on elves, and a baby born with a birthmark or deformity was called "elf marked."
Indeed, our forefathers trifled with elves at their peril. According to folklorist Carol Rose in her encyclopedia "Spirits, Fairies, Leprechauns, and Goblins," though elves were sometimes friendly toward humans, they were also known to take "terrible revenge on any human who offends them. They may steal babies, cattle, milk, and bread or enchant and hold young men in their spell for years at a time. An example of this is the well-known story of Rip Van Winkle."
== Evolving elves ==
Another type of elf emerged, one with a somewhat different nature and form than the mischievous and diminutive sprites of yore. Some elves, such as those depicted in J.R.R. Tolkien's "Lord of the Rings" trilogy, are slender, human-sized, and beautiful, with fine — almost angelic — features. Tolkien's characters were drawn largely from his research into Scandinavian folklore, and therefore it's not surprising that his elves might be tall and blond. Though not immortal, these elves were said to live hundreds of years. They have also become a staple of modern fantasy fiction.
Gary Gygax, co-creator of the seminal role-playing game Dungeons and Dragons, was not only influenced by Tolkien's elves but also instrumental in popularizing them, even including elves as one of the character races (along with humans) that gamers could play.
In either form, elves are strongly associated with magic and nature. As with fairies, elves were said to secretly steal healthy human babies and replace them with their own kind. These changelings appeared at first glance to be human babies, but if they became seriously sick or temperamental, parents would sometimes suspect that their own child had been abducted by elves. There were even legends instructing parents on how to get their real child back from its elven abductors.