as King of the Dál gCais (the earliest extant usage of this dynastic name) and Abbot of Tuaim Gréine and in the same year his son was killed by one of the sons of Lorcáin mac Lachtna (who is said to succeed Rebeacán as king), the annals report "Duibhghiolla, son of Robacáin, Lord of Ua Corbmaic, was murdered by Congalach son of Lorcáin in treachery". This action must have paved the way for Lorcán and his sons to seize power. Lorcán was descended from the Uí Toirdhealbhach instead of the Uí Oengusso who had hitherto comprised the Deisi Tuaiscirt kings. Cinnéidigh, another son of Lorcáin, who became king after his father, expanded the power of the Dál gCais greatly and was noted as King of Thomond in the annals by his death. His son Mathgamain built on his achievements, capturing Cashel and becoming King of Munster. The best-known member of this dynasty, Brian Boru, took over after his brother Mathgamain's death, reclaimed the Munster kingship and eventually succeeded in establishing himself as High King of Ireland before his famous death in the Battle of Clontarf. The Dál gCais under Brian's descendants, the Ua Briain would provide a further three High Kings of Ireland and exercised supremacy in Munster until Tairrdelbach Ua Conchobair, taking advantage of war between brothers Diarmait and former High-King Muircheartach, invaded Munster and split it in two in the Treaty of Glanmire (1118) granting Thomond to the sons of Diarmait Ua Briain and Desmond to the leading sept of the dispossessed Eoganacht, the Mac Cárthaigh dynasty. After the death of Domnall Mór Ua Briain, a claimant to the Kingship of Munster, they further retreated beyond the Shannon into the area of modern County Clare in the wake of the Norman Invasion. In 1276 King Edward II granted all of Thomond to Thomas de Clare, taking advantage of the feuding between Clann Taidhg and Clann Briain (whom de Clare supported). The de Clares failed in conquering Thomond and were decisively defeated in the Battle of Dysert O'Dea in 1318, thus the Kingdom of Thomond remained outside of foreign control for a further 200 years. In 1543 Murchadh Carrach Ó Briain, agreed to surrender his Gaelic Royalty to King Henry VIII and accepted the titles Earl of Thomond and Baron Inchiquin. At his death in 1551 the Earldom passed to his nephew Donough by special remainder and the title