Part II. History of Thomond
Chapter 12. History of Thomond before it was formed into an English county: From the earliest times, to the death of De Clare, and expulsion of the English in 1318.

Conor-na-Suidaine O’Brien sends his son to a meeting of the Irish provincial kings at Caeluisce; Importance of that meeting as deciding the future destiny of Ireland; Fatal decision arrived at; Monument of Conor-na-Suidaine O’Brien at Corcomroe Abbey

The death of Donogh Cairbreach occurred in 1242, and he was succeded by his eldest son, Conor-na-Suidaine. At his death, Donogh’s kingdom comprised the country lying between Loop Head and Birr, thence by Cashel, round by Knockaney, to the bay of Galway. His residence, at Clonroad, is described as an earthen fort, of a round form, and this fortress continued for generations to be the principal home of the O’Brien. Donogh Cairbreach was the first who was styled The O’Brien. ^[33]

A.D. 1258. Teige Cael-Uisce O’Brien.
As if things were not bad enough already, a new element of strife now begins to appear in the story of the O’Briens, namely the English invaders. In the south of Munster, these began to grow powerful, and they sought to extend their power to the northern parts of the province also. Conor na-Suidaine, however, was determined to preserve his territories intact, and in 1257 he gave battle to and defeated the enemy. Again, in 1257, he attacked and worsted them on the Galway side of his kingdom. At length, it appeared to the Irish, that their only hope of safety from the aggressions of the stranger was union amongst themselves. They saw that, by keeping asunder, they would become the prey in detail, of an astute enemy, who omitted no opportunity of fomenting their differences. A general meeting of the provincial kings of Ireland was therefore convoked, at a place called Cael-uisce, on Lough Erne, near the present Castle Calwell, and Conor O’Brien, being unable to attend in person, sent his eldest son Teige, called in after times, from that incident, Teige Cael-uisce, to represent him in the assembly (A.D. 1258). As the best means of resisting the English, it was proposed, that one supreme king of Ireland should be acknowledged, with full powers vested in him, to call out and command the forces of the whole country. This was agreed to, but when it came to the selection of the supreme ruler, a contest arose between O’Neill and O’Brien as to which of the two should be the man to be chosen. O’Neill’s right was regarded as paramount and unquestionable, but O’Brien would not yield, and as a consequence, the conference broke up without arriving at any definite settlement of the question. Since Ireland was first inhabited up to the present day, no act more fatal to her true interests ever happened than this. The opportunity was lost, never to return, of annihilating the power of England, then in its weakness. The example of Brian Boroimhe, who by means of his sole sovereignty over the whole island was able to extirpate the Danes, was forgotten by his descendant Teige Cael-uisce, and by his act of vain folly, the island has since remained a scene of anarchy, fomented by the machinations of the unscrupulous stranger. ^[34] Teige died in the following year, but it had been better for his country that he was never born. ^[35]