Cú Roí in the context of Dáire

The Kingdom of Munster (Irish: Ríocht Mhumhan) was a kingdom of Gaelic Ireland which existed in the south-west of the island from at least the 1st century BC until 1118. According to traditional Irish history found in the Annals of the Four Masters, the kingdom originated as the territory of the Clanna Dedad (sometimes known as the Dáirine), an Érainn tribe of Irish Gaels. Some of the early kings were prominent in the Red Branch Cycle such as Cú Roí and Conaire Mór. For a few centuries they were competitors for the High Kingship of Ireland, but ultimately lost out to the Connachta, descendants of Conn Cétchathach. The kingdom had different borders and internal divisions at different times during its history.

Major changes reshaped Munster in the 6th century, as the Corcu Loígde (ancestors of the Ó hEidirsceoil) fell from power. Osraige which had been brought under the control of Munster for two centuries was retaken by the Dál Birn (ancestors of the Mac Giolla Phádraig). Various subordinate groups, such as the Múscraige, switched their alliance and helped to bring the Eóganachta to power in Munster. For the next three centuries, various subgroups such as the Eóganacht Chaisil (ancestors of the Ó Súilleabháin and Mac Cárthaigh) and Eóganacht Glendamnach (ancestors of the Ó Caoimh) competed for control of Munster. Celtic Christian civilisation developed at this time and the Rock of Cashel became a seat of power. Two kings, Faílbe Flann mac Áedo Duib and Cathal mac Finguine, were able to raise Munster to the premier Irish kingdom for a time.

Fled Bricrenn (Old Irish "Bricriu's Feast") is a story from the Ulster Cycle of Irish mythology. Bricriu, an inveterate troublemaker, invites the nobles of the Ulaid to a feast at his new bruiden (hostel, banquet hall) at Dún Rudraige (Dundrum, County Down), where he incites three heroes, Cúchulainn, Conall Cernach, and Lóegaire Búadach, to compete for the "champion's portion" of the feast. The three heroes perform several feats, and travel to Connacht to be judged by Ailill and Medb, and to Munster to be judged by Cú Roí. On each occasion, Cúchulainn is proclaimed champion, but the other two competitors refuse to accept their losses. Eventually, back at Emain Macha, the three heroes are each challenged by a giant churl to cut off his head, on the condition that they allow him to cut off their heads in return. First Lóegaire, then Conall, takes up the challenge and cuts off the churl's head, only for him to pick it up and leave, but when the churl returns the following night they are nowhere to be seen. Only Cúchulainn lives up to his side of the bargain by agreeing to be beheaded. The churl spares his life, reveals himself to be Cú Roí in disguise, and announces that Cúchulainn's bravery and honour make him an undisputed champion.

The story dates from the 8th century and is found in several manuscripts, including the Lebor na hUidre (c. 1106). The motif of warriors competing for the champion's portion is found in another Ulster Cycle tale, Scéla Mucce Maic Dathó ("The Tale of Mac Dathó's Pig"), and is reminiscent of descriptions of customs of the Celts of continental Europe as recorded by classical authors. The beheading challenge also has classical parallels, and appears in later medieval literary works like Sir Gawain and the Green Knight.