[1] His father Colcú mac Bressail (died 722) was called king of Ard Ladrann (near Gorey, Co.Wexford) at his death obit in the annals in 722 which mention that he was killed.
Their armies under the king Murchad mac Brain Mut (d.727) met at the battle of Allen where Fergal was killed.
The saga Cath Almaine preserves the story of this battle and mentions that Áed mac Colggen fought for Leinster where he is referred to as heir-apparent.
The Annals of Ulster say:[8] And men say that so many fell in this great battle that we find no comparable slaughter in a single onslaught and fierce conflict throughout all preceding ages.
[citation needed] Aed was succeeded as king of Uí Chennselaig by his brother Sechnassach mac Colggen (died 746/747).