Снорри Стурлусон
It was written in "c." 1225 by Snorri Sturluson, who made use of the saga by the priest Styrmir Kárason, now largely lost except for some fragments in "Flateyjarbók". A revised version of the Separate Saga was later incorporated into the "Heimskringla" ("c." 1230), often ascribed to Snorri Sturluson.