We begin to discern in this reign that royal marriages have much to do with war and politics. Hugh, the late king, left a widow, named Maelmara ("follower of Mary"), daughter to Kenneth M'Alpine, King of the Caledonian Scots: this lady Flan married. The mother of Flan was the daughter of Dungal, Prince of Ossory, so that to the cotemporary lords of that borderland the monarch stood in the relation of cousin. A compact seems to have been entered into in the past reign, that the _Roydamna_, or successor, should be chosen alternately from the Northern and Southern Hy-Nial; and, subsequently, when Nial, son of his predecessor, assumed that onerous rank, Flan gave him his daughter Gormley, celebrated for her beauty, her talents, and her heartlessness, in marriage. From these several family ties, uniting him so closely with Ossory, with the Scots, and with his successor, much of the wars and politics of Flan Siona's reign take their cast and complexion. A still more fruitful source of new complications was the co-equal power, acquired through a long series of aggressions, by the kings of Cashel. Their rivalry with the monarchy, from the beginning of the eighth till the end of the tenth century, was a constant cause of intrigues, coalitions, and wars, reminding us of the constant rivalry of Athens with Sparta, of Genoa with Venice. This kingship of Cashel, according to the Munster law of succession, "the will of Olild," ought to have alternated regularly between the descendants of his sons, Eugene More and Cormac Cas—the Eugenians and Dalcassians. But the families of the former kindred were for many centuries the more powerful of the two, and frequently set at nought the testamentary law of their common ancestor, leaving the tribe of Cas but the border-land of Thomond, from which they had sometimes to pay tribute to Cruachan, and at others to Cashel. In the ninth century the competition among the Eugenian houses—of which too many were of too nearly equal strength—seems to have suggested a new expedient, with the view of permanently setting aside the will of Olild. This was, to confer the kingship when vacant, on whoever happened to be Bishop of Emly or of Cashel, or on some other leading ecclesiastical dignitary, always provided that he was of Eugenian descent; a qualification easily to be met with, since the great sees and abbacies were now filled, for the most part, by the sons of the neighbouring chiefs. In this way we find Cenfalad, Felim, and Olcobar, in this century, styled Prince-Bishops or Prince-Abbots. The principal domestic difficulty of Flan Siona's reign followed from the elevation of Cormac, son of Cuillenan, from the see of Emly to the throne of Cashel.