The Síl nÁedo Sláine dominated the midlands in this period and began to engage in internecine strife among its various lineages.
Congalach's first mention in the annals is in 688 when he was defeated at the Battle of Imlech Pich by Niall mac Cernaig Sotal of the Uí Chernaig sept of Lagore in south Brega.
[2] Congalach survived the battle but his allies Dub dá Inber, king of Ard Ciannachta, and Uarchride Ua Oissíne, of the Conaille Muirtheimne, were slain.
[3] In 695, Congalach and his kinsman Áed mac Dlúthaig of the Síl nDlúthaig of Fir Cúl Breg killed Fínsnechta Fledach, the High King of Ireland, and his son Bresal of the Clan Fínsnechtai sept at Grellaigh Dollaith.
[5] The record in Annals of Ulster may show that Congalach was a candidate for the high kingship after the killing of Fínsnechta, in competition with Loingsech mac Óengusso of the northern Uí Néill kindred of Cenél Conaill.