The system in effect was a dynastic monarchy but family-elected and aristocratic, in the sense that the royal family chose the most suitable male candidate from close paternal relations—roydammna (those of kingly material) rather than the crown automatically passing to the eldest son.

Since 1542, as a part of the Peerage of Ireland, the head of the Ó Briain house adopted primogeniture to decide succession of noble titles instead.

[4] While founder mythologies were very common in antiquity and the medieval world, such a connection is generally regarded as fanciful and politically motivated in the context of the rise to prominence of the Dalcassians.

Taken from the weakened Uí Fiachrach Aidhne it had previously been part of Connacht but was renamed Thomond (Tuamhain, meaning North Munster).

[4] Mathgamain along with his younger brother Brian Boru began military campaigns such as the Battle of Sulcoit, against the Norse Vikings of the settlement Limerick, ruled by Ivar.

The Dalcassians were successful, plundering spoils of jewels, gold and silver, saddles, finding "soft, youthful, bright girls, booming silk-clad women and active well-formed boys".

[6] Mathgamain was only defeated in the end by a piece of treachery; he believed he was attending a friendly meeting, but was betrayed at Donnubán mac Cathail's house, handed over to his enemies and executed in 976.

[9] The crown of Munster was briefly back in the hands of the Eoghanachta for two years until Brian Boru had thoroughly avenged his brother,[10] with the defeat and slaying of Máel Muad in the Battle of Belach Lechta.

[citation needed] The war dragged on but Brian would eventually force Máel Sechnaill to accept his authority when northern branch of the Uí Néill clan refused to support him.

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.

[13] 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.