 Ragnarssona þáttr ("The Tale of Ragnar's sons") adds a great deal of colour to accounts of the Viking conquest of York.This associates the semi-legendary king of Sweden Ragnar Lodbrok and his sons, Hvitserk, Björn Ironside, Sigurd Snake-in-the-Eye, Ivar the Boneless, and Ubbe.According to the stories, Ragnar was killed by Ælla, and the army which seized York in 866 was led by Ragnar's sons who avenged his death by subjecting Ælla to the blood eagle.