This paper has a double purpose: firstly, to assess the importance of seiðr magic rituals and of its practitioners within the social and mythological framework of Old norse-icelandic Literature. Secondly, by means of the analysis of certain scenes in The Saga of Gísli Súrsson, i aim to demonstrate that the inclusion of magic-religious motifs in the Sagas of icelanders has a triple objective: to provide a model to help understand apparently inexplicable phenomena, to intensify the tragic tone of the plot (...) and finally to depict those involved in the performance of seiðr in a very negative light. (shrink)