The essays in this book examine various manifestations of monstrosity in the early literatures of England, Ireland and Scandinavia. The dates of the texts discussed range from the eighth to the thirteenth centuries and were written either in Latin or in one of the vernaculars. The present contributions shed light on the physical, mental and metaphysical qualities that characterize medieval monsters in general. How do such creatures relate to accepted physical norms? How do their behaviours deviate from established cultural practices? How can their presence in both fictional and non-fictional texts be explained either in terms of a textual tradition or as a response to actual events? Such issues are examined from literary, philological, theological, and historical points of view in order to provide a thorough, multifaceted depiction of the sub- and supernatural monsters of medieval Northwest Europe.