In the 6th and 7th centuries, the Dál nAraidi were part of a confederation of Cruthin tribes in Ulaid and were the dominant dynasty. Ailill belonged to a branch of this family settled in Eilne, a plain between the Bann and Bush rivers in modern-day County Antrim, Northern Ireland. He is styled "King of the Cruithne" in the Fragmentary Annals' of Ireland.[2] The annals record that Ailill was killed, but the circumstances are not mentioned.[3]