According to this myth there were three kings of the Dedannans reigning in Ireland at the coming of the Milesians, named MacColl, MacKecht and Mac Grena.
Through an elder line from Neill Mor was descended Brian Mac Phelim O'Neill, who was treacherously seized in 1573 by the earl of Essex, whom he was hospitably entertaining, and executed together with his wife and brother, some two hundred of his clan being at the same time massacred by the orders of Essex.
Of many separate treatises dealing with special branches of the law, the Book of Aicill, composed of opinions or placita of King Cormac Mac Art, otherwise Cormac ua Quim, Ard-Rig of Erinn from A.D.
In the 1st century of the Christian era, when Conchobhar or Conor Mac Nessa was king of Ulster, a crisis was reached, the result of which was that no man was allowed to act as Brehon until he had studied the full law course, which occupied twenty years, and had passed a rigorous public examination.
Prominent among them were Manannan mac Lir, who is connected with the sea and the Isle of Man, and the Dagda, the father of a numerous progeny.