Baba Yaga is a great source of nightmares. I’ve said it before, but of all the creatures, spirits or entities out of Slavic folklore–she’s the one who freaks me out the most. Far more than any other that I know of, even Koschei isn’t nearly as frightening, not to me.
Ivan Bilibin is one of my favorite artists. I love his style, and the subject matter. Fairy tales have always been a weak spot of mine (I still adore reading versions even to this day–and I’ve got 2 copies of the Brothers’ Grimm, 1 English and 1 German–as well as my other fairy tale collections). And there’s just something beautiful about his work.