Cú Roí mac Dáire

Cú Roí (Cú Ruí, Cú Raoi) mac Dáire is a king of Munster in the Ulster Cycle of Irish mythology. He is usually portrayed as a warrior with superhuman abilities and a master of disguise possessed of magical powers. His name probably means "hound of the plain/field", or more specifically, "hound of the battlefield". He is the son of Dáire mac Dedad (or Dáire Doimthech), and thus belongs to the Clanna Dedad. However, T. F. O'Rahilly believed this to be artificial, stating that "Cú Roí and Dáire are ultimately one and the same".

Though often an outsider figure, for instance in the role of intervener or arbitrator, Cú Roí appears in a great number of medieval Irish texts, including Forfess Fer Fálgae, Amra Con Roi, Brinna Ferchertne, Aided Chon Roi (in several recensions), Fled Bricrenn, Mesca Ulad and Táin Bó Cúailnge. The early Irish tale-lists refer to such titles as Aided Chon Roí, Echtra Chon Roí (List A), Orgain Chathrach Chon Roí and Cathbúada Con Roí (List B), but only the first of these tales can be shown to have survived in some form. Several tales describe the enmity between him and the Ulster hero Cú Chulainn, who eventually kills him.

Cú Roí plays an important role in the 8th-century tale Fled Bricrenn (Bricriu's Feast). The trickster Bricriu incites the heroes Cú Chulainn, Conall Cernach and Lóegaire Búadach to compete for the champion's portion at a feast, and Cú Roí is one of those who judged among them. Like all the other judges, he chooses Cú Chulainn, but Conall and Lóegaire refuse to accept his verdict. When the three heroes return to Ulster, Cú Roí appears to each in the guise of a hideous churl (bachlach) and challenges them to behead him, then allow him to return and behead them. Only Cú Chulainn is brave and honourable enough to submit himself to the churl's axe, so he is declared champion. This story is related to the "beheading game" motif appearing in many later works in Arthurian literature - most famously the 14th-century English poem Sir Gawain and the Green Knight, although closer correspondences are to be found in Diu Crone and la Mule sans Frein, both of which feature a revolving fortress like Cu Roi's.

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