The Lost Wizard

Summary

There was once a wizard named Lost who refused to look for herself, afraid of what she might find. But she was envious of all those who were found. Her sorrow and angst leaked from her and spread like a disease throughout her town's children. Those affected began to find things and places unfamiliar. They began to feel like strangers in their own houses, in their own bodies, and among their own families. They began to wander, to find a place where they belonged.
Those who wandered were said to be drawn towards a land of mists where nothing would be familiar, but strangely brought them comfort. They would wander there until their legs and minds gave up and their minds were swallowed by the mist.
The few children who returned were no longer there in the head, barely conscious shells who fumbled through their days, mute aside from a nonsensical chorus they would all sing in unison every day.
The parents, seeking vengeance, traced these tragedies back to Lost. A mob burned her home, and forced her to seek out the Land of Mists to bring back their children. But she did not know where this land was, nor did she understand how she was causing this to happen.
She was exiled, forced to wander from village to village, where the same thing would happen.

Historical Basis

There were a series of kidnappings by malevolent Fey who abducted children into the Feywild. They occasionally returned children who did not suit their purpose, but because of the Feywild's magic, the children were severely mentally damaged. The Land of Mists is mentioned in the childrens' song and likely refers to the Feywild's Veil.

Spread

While the kidnappings were happening, there was no official explanation, so parents came up with this story to warn their children not to talk to strangers, in hopes of preventing these kidnappings.