The result was a conference of the tribe, who voted for war, and marched into the country of the Eoghanists (the present co. Kerry), who at once joined the standard of the Dalcassians. The Danes suffered severely in Munster. This aroused the Limerick Danes; and their chieftain, Ivar, attacked the territory of Dal-Cais, an exploit in which he was joined, to their eternal shame, by several native princes and tribes, amongst whom were Maolmuadh (Molloy), son of Braun, King of Desmond, and Donabhan (Donovan), son of Cathal, King of Ui Cairbhri. The result was a fierce battle at Sulcoit, near Tipperary, wherein the Danes were gloriously defeated. The action was commenced by the Northmen. It continued from sunrise till mid-day, and terminated in the rout of the foreigners, who fled “to the ditches, and to the valleys, and to the solitudes of the great sweet flower plain,” where they were followed by the conquerors, and massacred without mercy.
The Dalcassians now obtained possession of Limerick, with immense spoils of jewels, gold and silver, foreign saddles, “soft, youthful, bright girls, blooming silk-clad women, and active well-formed boys.” The active boys were soon disposed of, for we find that they collected the prisoners on the hillocks of Saingel, where “every one that was fit for war was put to death, and every one that was fit for a slave was enslaved.” This event is dated A.D. 968.
Mahoun was now firmly established on the throne, but his success procured him many enemies. A conspiracy was formed against him under the auspices of Ivar of Limerick and his son, Dubhcenn. The Eoghanist clans basely withdrew their allegiance from their lawful sovereign, allied themselves with the Danes, and became principals in the plot of assassination. Their motive was as simple as their conduct was vile. The two Eoghanist families were represented by Donovan and Molloy. They were descendants of Oilioll Oluim, from whom Mahoun was also descended, but his family were Dalcassians. Hitherto the Eoghanists had succeeded in depriving the tribes of Dal-Cais of their fair share of alternate succession to the throne of Munster; they became alarmed at and jealous of the advancement of the younger tribe, and determined to do by treachery what they could not do by force. With the usual headlong eagerness of traitors, they seem to have forgotten Brian, and quite overlooked the retribution they might expect at his hands for their crime. There are two different accounts of the murder, which do not coincide in detail. The main facts, however, are reliable: Mahoun was entrapped in some way to the house of Donovan, and there he was basely murdered, in violation of the rights of hospitality, and in defiance of the safe-conduct of the bishop, which he secured before his visit.