Ideas and beliefs about subterranean beings are very common in Nordic culture, in both older myths and younger folklore, but have so far not been investigated in a more systematic way. In my doctoral thesis, I want to show how these representations differ between different genres in Norse (Fornish and Norwegian) literature from the Middle Ages onwards, and contribute new knowledge about this material. Representations of elves and similar subterranean creatures differ between, on the one hand, so-called Old Age tales, which are set in the distant past and are often translations or adaptations of continental stories, and, on the other hand, Icelandic tales set in or around the Middle Ages in Iceland. Further variants appear in poetry and in medieval Christian laws. Examples of different beliefs about elves and goblins, which appear in the Icelandic manuscript material, include that they live in the earth, often in a special hill or stone near the people's settlements, that they are pathogenic but also assist in curing diseases, that they bring good luck/bad luck to farms, hunting, fishing and similar activities. In some literary genres, these mythical beings also seem to legitimize land ownership and, in some cases, kingship.