Balor is the Celtic God of death, and the king of the Fomorians, a race of chaotic giant warriors. This race like to find a village, pillage and kill, and move on. When Balor was a boy, he looked upon a poisonous brew that his father Druid was creating. The fumes caused him to grow a huge poisinous eye, which when it looked upon someone they would die. So he often kept his eye closed, if for no other reason than to keep from tripping over dead bodies. [1,2]
It was prophesied that he would be killed by his grandson. So when his daughter Ethlinn was a young lady, he locked her in a crystal tower so that she would not become pregnant. With the help of the druidess Birog, Cian of the Tuatha Dé Danann, managed to enter the tower and slept with Ethlinn. She gave birth to a son, but when Balor learned of his existence he threw him in the ocean. Birog saved the boy and gave him to the sea god Manannan mac Lir, where he was raised. The boy, named Lugh Lamhfada (Lugh of the Long Arm), became a member of the Tuatha Dé Danann and led them in the second battle at Mag Tuireadh.
In this second, and final battle, Balor killed King Nuada of the Tuatha Dé Danann with a glance from his eye. But when he opened his eye to kill his grandson Lugh, the latter managed to rip out Balor’s eye with a sling and Balor fell dead to the ground.