Norse mythology is the whole of myths, legends and beliefs attached to them, that existed in North Germanic countries in pre-Christian times. In a sense, Norse mythology is part of Viking religious tradition or Norse paganism. Our knowledge of it derives from early written materials, ancient works of art, such as runestones, archaeology and etymology. Of utmost importance are written materials such as Eddas and Heimskringla by Snorri Sturluson. The Prose or Younger Edda was written in the 13th century. It explains kennings or metaphors of skaldic poetry, which often include various notions belonging to Norse mythology. The Elder or Poetic Edda was written down about 50 years later but it includes the material dating back to much earlier times. It contains poems that deal with Norse deities and heroes.
Photo: Tjängvide image stone. Norse mythology scene including Odin who enters Valhalla riding on Sleipnir. Courtesy Mararie. Used under the Creative Commons Attribution-Share-Alike 2.0 Generic Licence.