In the Táin Bó Cuailnge [Cattle Raid of Cooley], he is a fighter for the Ulster forces, but known as a man of generosity and a bloody blade. He has silver-grey hair and carries only a silver spike as a weapon. When he is wounded, the Ulster forces take him to their camp. Although he kills the healers (fifteen or as many as fifty) who attempt to treat him, as he does not like their unfavourable diagnoses, the other Ulstermen listen patiently when he explains how he acquired his many wounds, one of which came from Medb. Cúchulainn helps to restore him with bone marrow and animal ribs. He goes back into battle, killing more Connachtmen before he himself falls. Cethern is also a teacher of Fionn mac Cumhaill in the Fenian Cycle. His father is Fintan mac Néill.