Devdutt distinguishes between mythological fiction and mythology. Korean dragons are legendary creatures in Korean mythology and folklore. A troll is a class of being in Norse mythology and Scandinavian folklore. They refer to the Harpies of Ancient Greek mythology. This is a list of demons that appear in religion, theology, demonology, mythology, and folklore. The dragons of Greek mythology were serpentine monsters. This is a list of dragons in mythology and folklore. Valhalla is the name of warrior's paradise in ancient Norse mythology. Dragons in Greek mythology often guard treasure. The Titan in the Greek mythology of Prometheus parallels Victor Frankenstein. Midgard is a realm in Norse mythology. It follows a fantasy plot based on Norse mythology. Mercury is the messenger of the gods in mythology. Influence from Greek mythology is also apparent. Euskal Herria retains numerous legends that account for an ancient mythology of witchcraft.