The broad agreement of generally pro-Uí Néill sources that Ailill was High King is offered as proof that this was the case. Although the chronology of 5th century High Kings has been the subject of manipulation, it is seen as unlikely that later historians and genealogists would have added a non-Uí Néill king had the belief that Ailill was king not been widespread. Ailill is said to have become High King following the supernatural death of Lóegaire mac Néill, supposedly c. 463. The Irish annals contain many references to him, but most of these are taken to be late additions, or come from the now lost Book of Cuanu, extracts of which are preserved in the Annals of Ulster. Tradition has him killed in battle at Faughan Hill, fighting against the sons of Niall. The king lists say that he was succeeded by Lugaid mac Lóegairi.