Lagertha's tale is recorded in passages in the ninth book of the Gesta Danorum, a twelfth-century work of Danish history by Saxo Grammaticus [REF].
After returning to Denmark to fight a civil war, Ragnar (who, according to Saxo, was still annoyed that Lagertha had set beasts against him) divorced Lagertha in order to marry Thora Borgarhjört (Þóra Borgarhjǫrtr), daughter of King Herraud (Herrauðr) of Sweden [REF].