George Borrow,
Once a Week, Series 1, Volume IX…
(1863)
“ After some time, Hakon, seeing that he is on the point of being vanquished, goes on shore, and invokes the assistance of two female demons, Thorgerdr and Yrpr, to whom he sacrifices his son Erling, a beautiful boy, seven years old. The fiends forthwith raise a storm of hail and lightning against the Jomsvikingar, so dreadful that Sigvald and the greater part of his people take to flight. ”
