Nial IV. (surnamed _Black-Knee_) succeeded his father-in-law, Flan of the Shannon (A.D. 916), and in the third year of his reign fell in an assault on Dublin; Donogh II., son of Flan Siona, reigned for twenty-five years; Congal III. succeeded, and was slain in an ambush by the Dublin Danes, in the twelfth year of his reign (A.D. 956); Donald IV., in the twenty-fourth year of his reign, died at Armagh, (A.D. 979); which four reigns bring us to the period of the accession of Malachy II. as _Ard-Righ_, and the entrance of Brian Boru, on the national stage, as King of Cashel, and competitor for the monarchy. The reign of Nial _Black-Knee_ was too brief to be memorable for any other event than his heroic death in battle. The Danes having recovered Dublin, and strengthened its defences, Nial, it is stated, was incited by his confessor, the Abbot of Bangor, to attempt their re-expulsion. Accordingly, in October, 919, he marched towards Dublin, with a numerous host; Conor, son of the late king and _Roydamna_; the lords of Ulidia (Down), Oriel (Louth), Breagh (East-Meath), and other chiefs, with their clans accompanying him. Sitrick and Ivar, sons of the first Danish leaders in Ireland, marched out to meet them, and near Rathfarnham, on the Dodder, a battle was fought, in which the Irish were utterly defeated and their monarch slain. This Nial left a son named Murkertach, who, according to the compact entered into between the Northern and Southern Hy-Nial, became the _Roydamna_ of the next reign, and the most successful leader against the Danes, since the time of Malachy I. He was the step-son of the poetic Lady Gormley, whose lot it was to have been married in succession to the King of Munster, the King of Leinster, and the Monarch. Her first husband was Cormac, son of Cuilenan, before he entered holy orders; her second, Kerball of Leinster, and her third, Nial _Black-Knee_. She was an accomplished poetess, besides being the daughter, wife, and mother of king's, yet after the death of Nial she "begged from door to door," and no one had pity on her fallen state. By what vices she had thus estranged from her every kinsman, and every dependent, we are left to imagine; but that such was her misfortune, at the time her brother was monarch, and her step-son successor, we learn from the annals, which record her penance and death, under the date of 948.