 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.Áed appears as a rival to the Leinster throne during the reign of Fáelán mac Murchado (died 738) at a time when Cathal mac Finguine (died 742), King of Munster, was attempting to assert his rights over Leinster during a time of Uí Neill weakness.