Once upon a time the people of Europe lived in fear of strange human-appearing monsters who came in the night to terrorize the community. These dread creatures were known by various names—the elves, the fae, the Fair Folk, the Sidhe.

Elves would creep into your home at night and steal your child, leaving one of their own inhuman spawn in its place. If not appeased they would blight your crops, sicken your livestock, and sour the milk. According to some, they paid a tithe of human souls to Hell every seven years. They could appear beautiful and alluring, but were soulless and whimsical, capable of killing without scruple or mercy.

Then the Romantics came along, and the old folk-tales began to change. The stories began…