Hey, someone's showed up at our glass mountain and eaten our food!The Seven Ravens
is a German Fairy Tale
collected by the Brothers Grimm
A family with seven sons finally has a daughter. She is sickly, and her father sends her brothers to get water for baptism. They, in their eagerness to obey, drop the jug in the well. The father, thinking they are playing, curses them, and they turn into ravens.
The girl, growing up, learns this. She goes to find them. She meets the sun, which frightens her off, and the moon, which does as well, but the stars are kindly and give her a drumstick, which she will need.
She finds the glass mountain where they live, and has lost her drumstick. She cuts off her finger and uses it to unlock the door. Her brothers fly back and are free from the curse.
Full text here