Mac Carthaig (MacCarthy), Domnall Mór (d. 1206), king of Desmond, succeeded when his father, Diarmait Mac Carthaig (qv), was murdered on 6 November 1185. After Domnall's inauguration, he captured and executed the murderer, Geoffrey de Cogan (qv). An able soldier and politician, who preserved the power of his dynasty against all comers, Domnall's reign was marked by the continuation of long-standing difficulties besetting his kingdom. The uncertain and vulnerable northern border of Desmond provided avenues for continual attacks from both the Uí Briain (O'Briens) and the Anglo-Normans, and much of his energy was directed towards the consolidation of Mac Carthaig power in this strategic region. Within his kingdom he had also to contend with the powerful and restless nobility of Desmond.
Like his father, Domnall maintained close diplomatic links with the ruling Uí Chonchobair (O'Connor) dynasty of Connacht and acknowledged Conchobar Máenmaige Ua Conchobair (qv), king of Connacht, as his overlord through the acceptance of a stipend in 1189. He further strengthened his regional position in 1190 by defeating a large Anglo-Norman host and concluding a peace with Domnall Ua Briain (qv), king of Thomond. In 1193 he served a warning to his family rivals by killing Cathal Odhar Mac Carthaig, the tánaiste of Desmond. In the same year trouble broke out again on his northern border: according to the Annals of Inisfallen, the Anglo-Normans, with Uí Briain assent, constructed a castle at Brí to support raids into northern Desmond. In 1194 a new dynastic pretender threatened his supremacy – his uncle Fíngen. Domnall quickly captured the challenger but seems to have released him soon afterwards. Fíngen then allied with the Uí Briain and together they killed Donnchad Ó Donnbáin (O'Donovan), Domnall's ally, in 1196. In a series of battles during that year, Domnall emulated the earlier success of his father by temporarily reversing part of the Anglo-Norman sub-infeudation of northern Desmond, and even burned Limerick. It seems that he may have gone to Connacht to confer with Cathal Mór Crobderg Ua Conchobair (qv), king of Connacht, when an Anglo-Norman army attacked the south of Desmond. The nobility was loyal to Domnall and, with the aid of bowmen sent by Cathal Crobderg, defeated the invaders. On his return, Domnall, with Cathal Crobderg, launched a counter-attack that swept to the gates of Cork. The annals in Mac Carthaigh's Book suggests that Domnall captured Cork but, despite the counsel of Cathal Crobderg and many nobles, decided against its destruction. The appearance of a fresh Anglo-Norman army in Desmond led to a truce, and Domnall made his own terms for surrendering Cork to them, according to which they recognised his suzerainty over it. Peace, however, was short-lived and Desmond remained a land of war until the close of the twelfth century.
In 1200 Domnall again faced a revolt of his vassals. He seems to have defused emerging trouble in Kerry by capturing Muirchertach Ó Muirchertaig (O'Moriarty), king of Eóganacht Locha Léin, and leading a successful campaign against rebels in the south-western regions of Desmond. These troubles may have been connected to the deposition of his ally Cathal Crobderg as king of Connacht by the Anglo-Normans in the same year. After his release by Hugh de Lacy (qv), Cathal Crobderg travelled to Munster to solicit aid from Domnall and William de Burgh (qv) against Cathal Carrach Ua Conchobair (qv), the Anglo-Norman puppet king of Connacht. In 1201–2 de Burgh, with strong support from the Ui Briain, launched successive campaigns into Desmond intent upon Domnall's submission. This war of attrition was checked in 1201 by the intervention of the papal legate and the bishops of Munster, who negotiated a temporary peace; but the following year a further assault by de Burgo's forces obliged Domnall to come to terms. Cathal Crobderg's defeat of de Burgo in Connacht during 1202 reversed the position again and Domnall withdrew his submission. The unrest continued: in 1204 Domnall again defeated a large invading Anglo-Norman force and in the following year saw off the rebellion of Cathal son of Cathal Odar Mac Carthaig, his cousin. He died in 1206, leaving three recorded sons.
Domnall's brother Fíngen succeeded him, but his son, Diarmait Dúna Droignéin Mac Carthaig (d. 1229), more commonly called Diarmait Cluasach (the long-eared), deposed Fíngen within months, resulting in widespread warfare throughout Desmond. The annals are divided on the date of Diarmait's accession. It is certain he was king of Desmond following Fíngen's death at the hands of the Uí Shúilliubáin (O'Sullivans) in 1209. Two years later the sheriff of Cork captured Diarmait, but when Cormac Óc, the son of Cormac Liathánach, established himself as king of Desmond, Diarmait was released and a dynastic war erupted between the claimants. With their respective Anglo-Norman allies they devastated much of Desmond in 1214. Diarmait seems to have been closely allied to the Anglo-Normans, as his marriage, about 1216, to Petronilla Bloet, the sister of the sheriff of Waterford, indicates. In 1218–19 Diarmait captured two Butler castles. Later Henry III wrote to him and to other Anglo-Norman and Gaelic Irish leaders on 17 July 1221 requesting their obedience to the new justiciar, Archbishop Henry of London (qv). In 1224 Domnall was part of an Anglo-Norman campaign against the sons of Hugh de Lacy (qv) (d. 1186) at Dundalk. According to the annals Diarmait was killed by a thunderbolt at his castle of Dún Draignéin (Castlemore in Muskerry East, Co. Cork) in 1229, which was seen as punishment for his evil deeds. He left one recorded son, Fíngen.