1 Sometime wife of Conall Cernach, his other consort being Lendabair. She is better remembered, however, for nursing Cúchulainn, during which time she becomes his mistress. She tries to stop Cúchulainn from leaving the fortress until he is healed, but Badb, daughter of Cailitin, puts a spell on Niam by impersonating one of her handmaidens and enticing her from the hero's bedside. The jealous Badb, seeking vengeance for Cúchulainn's killing Cailitin and all his male children, then takes Niam's shape and bids the hero rise from his bed and begin the journey that will lead to his death.
2 Daughter of Celtchair who agrees to marry Conganchnes mac Dedad to learn the secret of his seeming invulnerability. When she relates that her husband can only be killed with spears penetrating the soles of his feet and the calves of his legs, Celtchair quickly dispatches him. Later she marries Cormac Connloinges, son of Conchobar mac Nessa.
3 Lover of Oisín. In the oldest texts she is the daughter of Óengus (Angus) Tech, king of Munster, who elopes to Oisín to Ulster for six weeks, where she is pursued by her father and his retainers, dying of fear. In a second version she is the daughter of Áed Donn of Ulster, and it is over her that Oisín fights his first battle. Her best-known incarnation comes in Micheál Coimín's 18th-century Irish-language text, where she is called Niamh Chinn Óir [of the Golden Head/Hair]. Here she leads Oisín to a lengthy sojourn in Tír na nÓg [the Land of Youth], from which he returns to find himself greatly aged.