In Slavic mythology, there is a form of nymph which lies somewhere between a ghost and a fairy. The Wilas (pronounced viwa and also called Vili or Vilas) are fair-haired female creatures who have died but remain trapped between this world and the next. Mysterious beings similar in appearance to the European tales of fairies, they are the lost women who died unbaptized or the betrothed ones whose lives ended before marriage. Thus, unlike the European fairies, the mythological Wilas are not born as spirits of nature but rather become them with death, gaining power over the winds in lieu of the lives they would have led.
The knowledge of Wilas mostly stems from close readings of Polish and Slavic literature more than direct factual anecdotes. Wilas are mentioned in various poems and short stories, mostly as warnings to oblivious or unsuspecting men. What is best known of the Wilas, however, is their guises, their enjoyments, and most importantly, their temper. To begin, these lonely creatures—as previously mentioned—primarily have control over the winds. Because of this, they often tend to appear ghostlike or dressed in cloaks that billow in tune with the air. They can either blend into the wind as incorporeal shapes—translucent and intangible—or they can become solid, touching, and being touched, by the natural world around them. In each text, they are recorded as beautiful creatures, envied by human women and admired by mortal men, and they are commonly dressed beneath their cloaks in leaves or robes, or sometimes naked to entice the opposite sex.
Source : ancient-origins.net