God of smithing; member of the Tuatha Dé Danann and creator of their weapons. He is usually named together with Luichtne the carpenter, Creidne the wright, and Dian Cécht the leech. His Welsh counterpart is Gofannon.
Goibniu who was not impotent in smelting,
Luichtne, the free wright Creidne,
Dian Cécht, for going roads of great healing,
Mac ind Oc, Lug son of Ethliu.
--The Book of Invasions--
Goibniu was the smith of the Tuatha Dé Danann, and interestingly enough, we are never told of his parentage. However, if we take into consideration his Welsh counterpart of Gofannon, we can assume that he is the son of Danu and Bíle, and a brother of the Dagda and Dian Cécht.
Ruadan son of Bres and Brigit was sent to kill Goibniu during the second battle of Magh Turedh. As Ruadan was 3/4 de Dannan (and a grandson of the Dagda), the Fomorians felt that he would make a good spy. He asked for the impliments of a spear from Goibniu, and had the weapon assembled by a woman named Cron. Ruadan then took the spear and flung it at Goibniu who, although wounded, pulled out the spear and killed Ruadan. At his death, Brigit invented the practise of keening--that high-pitched wailing for the dead, sometimes associated with the beansidhe.
Goibniu then went to the Well of Slaine, provided over by Dian Cécht and his family, and was healed of his wounds by its magic waters. He then returned to battle, making weapons for the Dé Danann, who eventually won Ireland from the Fomorians.
1. The Book of Invasions--http://www.geocities.com/branwaedd/ebor4.html
2. The Second Battle of Magh Turedh. (various publications, websites)