The Skaggs-Files

Conn Cétchathach (Conn of the Hundred Battles) was a legendary High King of Ireland. He was the ancestor of the Connachta, and, through his descendant Niall Noígiallach, the Uí Néill dynasties. His father was Fedhlimidh Rachtmar and his mother was Ughna Ollchrothach. His son was Art mac Cuinn. Some stories of the Fenian Cycle are set in his time.

He gained the throne by overthrowing Mal, who had killed his father. He earned his epithet Cétchathach in his wars with the Dál nAraidi.

His rival for the kingship of Ireland was the king of Munster, Éogan Mór, also known as Mug Nuadat, who beat him in ten battles and took half of Ireland from his control. Mug was able to gain such power because his druid predicted a famine, which he prepared for by storing grain. Ireland is sometimes seen as divided between Leth Cuinn, Conn's Half, in the north, and Leth Moga, Mug's Half, in the south.

Mug was killed when Conn led a night attack against his forces with all of his tribal leaders save one behind him. Conn's forces ultimately overwhelmed Mug's army, and Mug was killed in the process.

Mal's son Tibride Tirech killed Conn at Tara, having sent fifty warrior dressed as women against him from Emain Macha.
(Wikipedia)

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The cast includes several major figures from Irish pseudo-history, Ailill Aulom, his son Éogan Mór and his step- and foster-son Mac Con, along with the King of Tara Art mac Cuinn. Mag Mucrama, the plain of the counting of the pigs, was in Connacht, in the region of Athenry, County Galway. A tradition or folk etymology, in Irish dindshenchas, has it that the plain was named for the magical pigs which infested it until banished by Queen Medb of Connacht.

Mac Con, exiled from Ireland, returns with the aid of the king of Britain, along with an army of Britons and Saxons, and conquers Ireland as far as Connacht where Éogan, with the help of Art mac Cuinn, plans to fight. The night before the battle Éogan and Art sleep with their hosts' daughters, conceiving the sons who will succeed them, Fiachu Muillethan in Éogan's case and Cormac mac Airt in Art's. Both Éogan and Art, as is foreseen, die in the battle at Mag Mucrama, and Mac Con becomes king of Tara.

Mac Con takes Cormac mac Airt as his foster son, and rules for seven years. He then pronounces a false judgement, showing that he is unfit to rule, while Cormac gives a right judgment, showing that he is the stuff of kings. Disasters ensue—"no grass came through the earth, nor leaf on tree, nor grain in corn" says the story—and Mac Con is deposed and Cormac made king in his place. Mac Con travels to Ailill's court, where his foster-mother warns him that he is in peril. When Ailill embraces Mac Con he bites him with his poison tooth, wounding Mac Con, who flees but is killed by one of Ailill's warriors.

https://en.m.wikipedia.org/wiki/Cath_Maige_Mucrama