Styrbiorn is Eddison's fleshing out of a story alluded to in the Eyrbygga and Heimskringla sagas.

A copy of this book exists, inscribed from Eddison to John Arlott, dated July 1943, with a note by Eddison: 'If I wrote this book to-day, it would end on p. 274. Eric.'  The book ends on pg. 284.