According to a prophecy, Balor, the god of the underworld was to be killed by his grandson. He locked his daughter, Ethlinn, in a tower made of crystal to keep her from becoming pregnant. However, Cian, one of the Tuatha de Danaan, with the help of the druidess Birog, managed to enter the tower. She gave birth to a son, Lugh, by him, but Balor threw him into the ocean. Birog saved him and gave him to Manannan mac Lir, who became his foster father. He was then nursed by Tailtiu.
Lugh was ingenious. One Irish tale relates of how the god travelled to Tara, and arrived during a feast for the royal court. Lugh was met by the gatekeeper, and was asked what talent he had, for it was a tradition there that only those who had a special ability could enter the palace. The god said: "I am a wright", to which the gatekeeper replied "We already have a wright, your services aren't needed here". Lugh persisted "I am a smith". Again, the guard said the court had a smith that was quite adequate; but the god was not to be dissuaded. Lugh then noted that he was also a champion, a swordsman nonpareil, a harpist, a hero, a poet, an historian, a sorcerer, and a craftsman. The gatekeeper merely nodded his head, and stated bluntly that all these trades were represented in the court by other members of the Tuatha de Danaan. "Ah, but you do have an individual who possesses all of them simultaneously?", was Lugh's clever reply. The guard was forced to admit his defeat, and so Lugh entered and joined the festivities.
Lugh Lamhfada led the Tuatha in the Second Battle of Mag Tuireadh against the Fomorians. During this battle, Balor killed King Nuada with his eye, but Lugh ripped the fatal eye out with a sling, killing Balor.
Lugh was husband of Rosmerta. After the god Nuada lost an arm in the Second Battle of Magh Tuiredh and was forced to abdicate his kingship since he was no longer perfect, Lugh became the leader of the Tuatha De Danaan.