In the Brothers Grimm tale “The Seven Ravens,” the sister cuts off her little finger to open the glass mountain’s door.
She has travelled to the glass mountain to rescue her seven brothers, who were transformed into ravens after their father angrily cursed them. At the mountain, she discovers that the key to the entrance has been lost. Because she cannot open the door normally, she cuts off her little finger and uses it to unlock the door.
Inside, she meets the ravens and reveals her identity. The brothers are restored to human form, although one remains slightly changed because the sister cannot complete every part of the transformation perfectly.
The tale is sometimes confused with “The Six Swans,” another Grimm story in which a sister rescues transformed brothers through years of silence and sewing. The two stories share the rescue motif but use different magical tasks.