Lugaid Riab nDerg

Lugaid Riab nDerg ("the red-striped") or Réoderg ("Red Sky"), son of the three findemna, triplet sons of Eochu Feidlech, and their sister Clothru was, according to medieval Irish legend and historical tradition, a High King of Ireland.

He was conceived of incest. The night before the three findemna, Bres, Nár and Lothar, made war for the High Kingship against their father in the Battle of Druimm Criaich, their sister Clothru, concerned that her brothers could die without heirs, seduced all three of them, and a son, Lugaid, was conceived. His epithet came from two red stripes around his neck and waist, dividing him into three: above the neck he resembled Nár; from the neck to the waist he resembled Bres; and from the waist down he resembled Lothar. Incest features further in Lugaid's story: he slept with Clothru himself, conceiving Crimthann Nia Náir.

The Lebor Gabála Érenn says he came to power after a five-year interregnum following the death of Conaire Mór (six years according to the Annals of the Four Masters). His foster-father, the Ulster hero Cúchulainn, split the Lia Fáil (coronation stone at Tara which roared when the rightful king stood or sat on it) with his sword when it failed to roar under Lugaid. It never roared again except under Conn of the Hundred Battles.

The wizared of Ethne, daughter of Eochaid Feidlech, prophesied that the son of Ethne's sister Clothru would kill her (Ethne). Therefore Ethne fled to Cruachan in the East to give birth to her son, but Lugaid chased her there and drowned her; he then cut her son, Furbaide Fer-benn (described as having two horns on his temples) from her womb. Later at the age of 17 Furbaide sought revenge against Lugaid for his mother's death, and killed Clothru, for which Lugaid killed Furbaide on a mountain top called Sliab Uillean. Certain elements of this story bear a resemblance to the prophecy of Lugh Lamhfhada, son of Ethniu, who was predicted to kill his grandfather Balor of the Evil-Eye.

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