Abstract The Old Norse medical corpus, both manuscript and epigraphic, illuminates understandings of the body and of the relationship between sickness, somatic emotion and the perceived integrity of the individual self in Viking and medieval Scandinavia. This essay argues that Old Norse medical texts and charms understand illness not only as an imbalance of humours but also as an invasive, anthropomorphised agent that seeks to breach the boundaries of the human body. Falling victim to illness is understood as a zero-sum power exchange, visualised through images of martial defeat and sexualised submission. Strong emotion can be rendered as physical illness in Old Norse literature because both forces threaten the integrity of the contained and individualised self. As a thematic case study, this essay examines runic healing charms, late medieval medical manuscripts and saga episodes dealing with boils and abscesses, which are attributed both to the surging of vital spirits and to the action of supernatural disease agents, to examine the way these texts understand the embodied self.