In Nordic folklore and mythology, a fylgja (Old Norse: , Old Swedish: fylghia, older Dalecarlian: fylgja) is a supernatural being or spirit which accompanies a person in connection to their fate or fortune. They can appear to people in their sleep as dream-women, or appear to them while awake, often in the disembodied spiritual form of an enemy.
Etymology
The word means "to accompany".
Fylgjur may also "mark transformations between human and animal" or, in other words, they may be shape shifters. In Egil's Saga, there are references to both Egil and Skallagrim transforming into wolves or bears, and there are examples of shape shifting in the Saga of King Hrolf Kraki, where Bodvar Bjarki turns into a bear during a battle as a last stand. These transformations are possibly implied in the saga descriptions of berserkers who transform into animals or display bestial abilities.
Else Mundal has argued that the animal fylgja and the woman-ghost type fylgja are of different origins, and the solitary animal fylgja is actually that individual's alter ego present since birth, which perishes together when that person dies.