Here's a link to a comprehensive article on domestic cats in Viking Age Scandinavia.
Abstract
The role of cats in Viking Age society is little investigated and has been dominated by un-critical adoptions of medieval mythology. Based on literary sources, the domestic cat is often linked to cultic spheres of female sorcery. Yet the archaeological evidence indicates an ambivalent situation. Cat bones from many trading centres show cut marks from skinning and highlight the value of cat fur. In contrast, the occurrence of cats in male burials points rather to a function as exotic and prestigious pets. The influence of Old Norse mythology on the traditional interpretation of cats as cultic companions therefore needs critical re-consideration. For this, a broad range of literary and historical sources – from Old Norse literature to Old Irish law texts – will be analysed and confronted with the archaeological evidence for domestic cats in Viking Age Scandinavia. The results will be discussed on a broader theoretical approach, involving concepts such as agency, and embedded in current research on human-animal-relations in order to achieve a more nuanced perspective on the roles and functions of cats in day-to-day reality as well as in the burial context.
Perhaps it helps with Ars Magica familiars and their history, or inspires a game about Viking Cats.