Ælla (or Ælle or Aelle, fl. 866; died 21 March 867) was King of Northumbria, a kingdom in medieval England, during the middle of the 9th century. Sources on Northumbrian history in this period are limited, and so Ælla's ancestry is not known and the dating of the beginning of his reign is questionable. In addition to the Anglo-Saxon Chronicle, Ælla is also mentioned in Scandinavian sources, such as the Norse sagas. According to the latter, Ælla captured the legendary Swedish-Danish Viking king Ragnar Lodbrok and put him to death in a pit of snakes. The historical invasion of Northumbria in 866 occurred in retaliation for Ragnar's execution, according to Ragnarssona þáttr (The Tale of Ragnar's Sons). While Norse sources claim that Ragnar's sons tortured Ælla to death by the method of the blood eagle, Anglo-Saxon accounts maintain that he died in battle at York on 21 March 867. Concerning the Norse claim, Roberta Frank reviewed the historical evidence for the ritual in her Viking Atrocity and Skaldic Verse: The Rite of the Blood-Eagle, where she writes: "By the beginning of the ninth century, the various saga motifs—eagle sketch, rib division, lung surgery, and 'saline stimulant'—were combined in inventive sequences designed for maximum horror." She concludes that the authors of the sagas misunderstood alliterative kennings that alluded to leaving one's foes face down on the battlefield, their backs torn as carrion by scavenging birds. If this is to be believed, then it is easy to surmise that the mention of his death via the blood eagle is in fact a description of his death on the battlefield, which would make both accounts of his death consistent. Anglo-Saxon accounts Ælla became king after Osberht (Osbryht) was deposed. The beginning of his reign is traditionally dated to 862 or 863 but evidence about Northumbrian royal chronology is unreliable prior to 867. His reign may have begun as late as 866. Almost nothing is known of Ælla's reign; Symeon of Durham states that Ælla had seized lands at Billingham, Ileclif, Wigeclif, and Crece, which belonged to the church. While Ælla is described in most sources as a tyrant and an illegitimate king, one source states that he was Osberht's brother. The Great Heathen Army, composed mostly of Danish, Norwegian and Frisian Vikings, landed in Northumbria in mid-866 and had captured York by 21 November. Subsequent events are described by historians such as Symeon