The Ulster Cycle is the great heroic saga-cycle of medieval Irish literature, centered on the kingdom of Ulster and its royal court at Emain Macha (modern Navan Fort near Armagh). The central figure is Conchobar mac Nessa, the king of Ulster, around whom a brilliant constellation of warriors gathers, the Red Branch knights. The greatest of these is Cú Chulainn, the semi-divine hero son of the god Lug, who stands as the supreme warrior of Irish tradition, comparable in many ways to Achilles in the Greek world. Other major figures include the mighty Fergus mac Róich, the tragic Deirdre and the sons of Uisliu, the warrior Conall Cernach, and the druid Cathbad. The cycle is written in a mixture of prose and poetry, with the prose narratives often being among the oldest surviving vernacular prose in any European language.
The centerpiece of the entire cycle is the Táin Bó Cúailnge, the Cattle Raid of Cooley, a great epic in which Queen Medb of Connacht and her husband Ailill lead a massive army into Ulster to steal the great brown bull of Cooley. Through a supernatural curse, all the warriors of Ulster are struck down by a debilitating weakness at the moment of crisis, leaving the young Cú Chulainn alone to defend the province in a series of single combats at river fords, including his most heartbreaking encounter, his battle to the death with his beloved foster-brother Fer Diad. The cycle is saturated with themes of honor, fate, loyalty, betrayal and doomed heroism, perhaps nowhere more powerfully than in the story of Deirdre, who is prophesied at birth to bring ruin to Ulster, and whose tragic love for Naoise son of Uisliu and ultimate destruction fulfills that prophecy with devastating inevitability.
