 According to the "Caithréim Conghail Cláiringhnigh" ("Martial Career of Congal Cláiringnech"), while Lugaid Luaigne was High King of Ireland, Fergus ruled the southern half of Ulster while Congal Cláiringnech ruled the northern half.The Ulaid objected to having two kings, and the High King was asked to judge which of them should be sole ruler of the province.Lugaid chose Fergus, and gave him his daughter Findabair in marriage.