He came to power when he defeated the previous High King, Dui Dallta Dedad, in the battle of Árd Brestine.
[2] After he had reigned for sixteen or twenty-five years, he paid a visit to Ulster.
While he was there, Eochu Feidlech, king of Connacht, raised an army and marched on Tara.
Eochu agreed, and named the battlefield as Leitir Ruad in the Corann, Connacht.
During the battle Eochu surrounded and beheaded Fachtna, and became High King in his place.