The Demon Invaders

What childhood stories are people still afraid of as adults in your world?
Every child of Numore grew up hearing about the demon invaders of legend. These demons, called the Selks, could be recognized by their pointed ears. Some bore red hair, though not all -- but it is said any child born of a demon to a human mother bore red hair, and for this reason red-haired children are still viewed with suspicion even today. (Note that not all, especially in rural communities, communities far from the Gornfar Mountains from whence the Selks came, or rural communities far from the mountains, remember the alleged cause of this prejudice; more often they remember that society frowns on such offspring but with unspecific reason.)

Locke pushed open the door, shoving into Galen. “Get on, you’re in the way. Da, there’s a man here says the red cow got into his peas and tramped all the young plants. Wants payment to plant new.”
“Curse that red thing,” snarled Idorn, “and all red things like her.”

Adults in Numore often dismiss the stories they heard as children, citing reasonably that demons do not actually invade their kingdom. But the more educated know that while this assertion is true, the Selks are not demons and do exist, and have invaded repeatedly through history.

Historical Basis

It is true that Numore was irregularly invaded by Selk warriors. No one could predict the timing of these incursions, which might occur over a century apart, and no demands or warnings ever heralded the Selk attacks. They would just appear on the eastern foothills and begin to ransack nearby villages. 
No such attacks have occurred in living memory, and some have denied that they were ever anything but legend, but the cultural memory lives on in the tales of demons coming from the mountains to attack the people of Numore.