Cairpre Nia Fer

Cairpre Nia Fer, son of Rus Ruad, was, according to medieval Irish legend and historical tradition, a king of the Lúaigni of Tara, although he is not included in the traditional list of High Kings of Ireland.

The earliest reference to Cairbre is in Tírechán's Memoir of St. Patrick, a 7th century Latin text found in the Book of Armagh. Patrick finds an enormous grave and raises its giant occupant from the dead. The giant says he was killed by the fian (a landless warband) of the sons of Mac Con during the reign of Cairbre Nia Fer, a hundred years previously – i.e. in the 4th century.

The 11th century Lebor Gabála Érenn places him during the reign of the High King Eterscél, which it synchronises his reign with that of the Roman emperor Augustus (27 BC - AD 14) and the birth of Christ, and makes him a contemporary of the provincial kings Conchobar mac Nessa of the Ulaid, Cú Roí of Munster and Ailill mac Máta of Connacht. Mac Con, placed a generation before Cairpre by Tírechán, is dated many generations after him, to the late 2nd century, in the Lebor Gabála. A later High King, Cairpre Lifechair, is killed in battle against the fianna and succeeded by the two sons of Mac Con, Fothad Cairpthech and Fothad Airgthech.

Alongside Conchobar, Cú Roí and Ailill, Cairpre appears in stories of the Ulster Cycle. His wife is Fedelm Noíchrothach, daughter of Conchobar, and they have a son, Erc, and a daughter, Achall. In Cath Ruis na Ríg ("The Battle of Rosnaree"), he and his brother Find mac Rossa, king of the Gailióin of Leinster, fight a battle against Conchobar and the Ulaid. The Ulaid hero Cú Chulainn kills him with a spear from distance, then decapitates him before his body hits the ground. After the Ulaid win the battle, Cairbre's son Erc swears allegiance to Conchobar, marries Cú Chulainn's daughter Finnscoth, and becomes king of Tara in his father's place.

Erc is later part of the conspiracy to kill Cú Chulainn. After avenging Cú Chulainn, Conall Cernach brings Erc's head back to Tara, where Achall dies of grief for her brother.