1 A king of Leinster, ally of Medb of Connacht, and key adversary of Cúchulainn, who kills Erc's father, Cairbre Nia Fer. In revenge Erc casts his spear into one of Cúchulainn's favourite horses, Liath Macha[Grey of Macha], just before Cúchulainn himself is killed by some of Erc's champions. Erc is subsequently killed by Conall Cernach.
2 Father of Eochaid mac Eirc, the admired king of the Fir Bolg.
3 One of the women of the Fianna in the Fenian Cycle.
4 Father of Fergus mac Eirc and Loarn of the Scottish Dál Riada. Many Highland genealogies trace family pedigrees back to Erc, and thus the phrase ‘sons of Erc’ might apply to many Scottish Gaelic families.