The Cajun people of Louisiana, Tennessee, and Virginia in the United States say that the feu-follet is the harmless, returned soul of a family member who escaped purgatory in order to beg its family for prayers and masses said in its name. The Irish people who settled near the Cajuns believe that the feu-follet are elves and fairies dancing, while the Basque claim that it is their guardian spirit warning of danger.

However, the African-Americans in the same areas believe that it a vampiric spirit. They say the feu-follet (“dancing light”) is the soul of a person that God sent back to earth to do penance, but rather than doing good, it decided to do evil instead. If a person sees it (a glowing orb of electricity that occasionally emits a lightning bolt), he must quickly stab his knife in the ground, as it may buy him just enough time to run home and change his clothing. If he does not, he will be struck by its lightning. Should he go back the following day to collect his knife, the blade will have blood on it.

Mischief makers, feu-follet also have INCUBUS- and SUCCUBUS-like tendencies in which they draw blood to drink. There is the belief that if a feu-follet can consume enough human blood, it will become a physical vampire.

Source: Boatright, The Golden Log, 115; Bryant, Handbook of Death, 99; Senn, Were-wolf and Vampire in Romania, 71; University of Missouri, University of Missouri Studies, vol.10, 75, 104