Hopcorn+

A beautiful and kind girl, daughter of Baba Yaga, finds a magical stone Alatyr while walking in a field. It transforms her heart into a stone and puts her under a queer curse. She is to be the evil Countess of Stones and live in a stone tower. If the greatest gem-cutter in the world brings the stone of Alatyr to life, though, she'll become the ruler of the world. The Stone Countess, now cruel and selfish, is fascinated with the idea. She starts searching for the best gem-cutters and forces them to work with Alatyr, so the magical stone would become a living thing. Neither of the gem-cutters succeeds, so she kills them. While being imprisoned in her tower, they work on a large book about the secrets of gem-cutting. Each of them edits the book, so it's later named "the Book of Masters".