Kupala
Kupala is a fictional goddess from Slavic stories. She symbolizes peace, water, magic, plants, and the ability to have babies, even though old Slavic folks didn't actually pray to her. She has a twin brother named Kupalo who stands for male ability to have babies. Together with other gods, they make up a god of fertility. There's a special celebration called  that her name comes from. The festival is actually Christian not pagan.