Norse mythology is a set of beliefs and stories shared by Northern Germanic tribes. It was not handed down from the gods to the mortal. It had no scripture. The mythology was passed on from one generation to the next in the form of poetry. It continued to be passed down this way through the time of the Vikings. The original beliefs were long lost. Our knowledge about it is mainly based on the Eddas and other medieval texts. These were written down while and after they turned to Christianity.