Meyer's Konverationslexikon defines Wiles or Wilis as female vampires, the spirits of betrothed girls who die before their wedding night.
According to Heine, wilis are unable to rest in their graves because they could not satisfy their passion for dancing when they were alive. They therefore gather on the highway at midnight to lure young men and dance them to their death. In Serbia they were maidens cursed by God; in Bulgaria they were known as samovily, girls who died before they were baptized; and in Poland they are beautiful young girls floating in the air atoning for frivolous past lives.
- The Romantic ballet Giselle, first danced in Paris in 1840, features spectral wilis, young girls who have died on their wedding days, who almost snatch away the hero's life-breath, but must disappear at the break of dawn. These wilis have been adapted from a poem of Heinrich Heine, who claimed to be using a Slavic legend.
- The first opera completed by Giacomo Puccini, Le Villi, makes free use of the same thematic material. It had its debut in May 1884 at the Teatro dal Verme, Milan, and was revised for a more successful reception at the Royal Theater, Turin, that December.