[2] Erca was born, along with her sister Pompa,[i] to an unknown mother and Loarn mac Eirc, a possible king of Dál Riata and a brother of Fergus Mór.
She gave birth to four sons in their marriage as well, including Feidhlimidh, the father of Saint Columba.
[3] Dubhaltach Mac Fhirbhisigh details in his Leabhar na nGenealach Erca's death after a pilgrimage from Irish Dál Riata back to Britain.
There she met her son-in-law, Saint Cairneach, who blessed her, told her half of Ireland's future kings would be her descendants, and promised her entry into heaven.
[5] Mac Fhirbhisigh writes that after Cairneach performed ecclesiastical ministrations ("friothaileamh eaglurdachta") on her, she died.