Teurst are demonic creatures in the folklore of Britanny (France).
The Dusii of Gaul are mentioned by St Augustine, who regarded them as incubi, and by Isidore of Seville, and in the name we may perhaps discover the origin of our expression the deuce!'.
- In the district of Morlaix, Teursapouliet or teursta poulict appears in the likeness of some domestic animal.
- In the district of Vannes is a colossal spirit called Teus, or Bugelnoz, who appears clothed in white between midnight and two in the morning. His office is to rescue victims from the devil, and should he spread his mouth over them they are secure from the Father of Evil. The Devil comes over the ocean; but, unable to endure the look of the good spirit, he sinks down again, and, the object of the spirit accomplished, he vanishes.