Cian

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, 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.