In ancient times, the concept of fairies was rather different. They were the often-dangerous embodiment of the land, dark and unpredictable spirits that watched Humanity with a jaundiced and hostile eye. And, according to conventional folk wisdom, they were to be feared rather than trusted. Indeed, in their original form, many of our "fairy tales” read more like late-night horror stories."
If you ever wondered about how dark fairies are, there's a book (the review of which starts with the above sentences) which will let you know everything about them. Click on the cover to read more about it