attacked Munster when he invaded northern County Clare, near the homeland of the Dál gCáis. However, a new rival emerged in the form of Domnall Mac Lochlainn, King of the Northern Uí Néill, who later in 1088 invaded Connacht and successfully gained the submission of Ruadhrí na Saide. Ruadhrí and Domnall formed an alliance and together they attacked Munster. At the time, Muirchertach was away campaigning in Leinster. They burned and looted Limerick, Killaloe and Emly, and took over 160 hostages. Muirchertach was forced to buy back these hostages with gold, silver, cattle and meat. According to a source from Munster, Muirchertach avenged himself by attacking the Kingdoms of Meath and Leinster, the latter presumably having fallen into enemy hands since the time Muirchertach had been governor of Dublin. He gained the submission of both provinces, killing the King of Leinster in the process. He also fought around Dublin, burning a building in Lusk, Fingal killing over 160 people inside. He then headed west and cut down the sacred inaugural tree of the Kings of Connacht. Muirchertach was involved in further naval actions against Connacht the next year in 1089 when he was looting islands in Lough Ree, but Ruadhrí na Saide blocked the path home on the River Shannon around the settlement of Clonmacnaoise, forcing Muirchertach to hand over his ships to the forces of the Kingdom of Meath after retreating to Athlone. He marched with his army back home to Munster on foot, but using Muirchertach's confiscated ships, the Meathmen and Connachtmen sailed southward on the Shannon and plundered the plains around Cashel. Four kings now battled for supremacy in Ireland: Muirchertach Ua Briain of the Kingdom of Munster, Domnall Ua Maél Sechnaill of the Kingdom of Mide, Ruadhrí na Saide Buide Ua Conchobhair of the Kingdom of Connacht, and Domnall Mac Lochlainn of the Northern Uí Néill. The four kings met in 1090, where Mac Lochlainn was acknowledged as High King of Ireland and he received hostages from the other three kings. Following this conference, Muirchertach went on campaign in Leinster again, but while he was away, Munster was attacked by Ua Maél Sechnaill who was joined by Ruadhrí na Saide. Although he was defeated by the Meath forces, he was able to drive the armies of Connacht back, and then received assistance from Mac Lochlainn in the north in defeating Ua Maél Sechnaill. Ruadhrí na Saide