Really creepy, as it develops.
From the "I want to believe" excitement and light to the rather dark mind-programming and its seemingly violent consequences.
It would be fascinating to see your whole concept developed.

In the town where I grew up there were stories (told as facts, with witnesses and all) about children kidnapped by duendes (showdow-like small creatures, allegedly children's ghosts). Kids who had experienced this were said to grow up as weird adults.