In Irish mythology, Balor (modern spelling: Balar) was king of named Fomorians, a group of supernatural beings. He is often described as a giant with a large eye in his forehead that wreaks destruction when opened. He has been interpreted as a god or personification of drought and blight.
It is suggested that Balor comes from Common Celtic *Baleros, meaning "the deadly one", cognate with Old Irish at-baill (dies) and Welsh ball (death, plague).
He is also referred to as Balor Béimnech (Balor the smiter), Balor Balcbéimnech (Balor the strong smiter) and Balor Birugderc (Balor of the piercing eye). The latter has led to the English name Balor of the Evil Eye.
Balor is said to be the son of Buarainech and husband of Cethlenn. Balor is described as a giant with an eye in the middle of his forehead. This eye wreaks destruction when opened. The Cath Maige Tuired calls it a "destructive" and "poisonous" eye that no army can withstand, and says that it takes four men to lift the eyelid. In later folklore it is described as follows: "It was always covered with seven cloaks to keep it cool. He took the cloaks off one by one. At the first, ferns began to wither. At the second, grass began to redden. At the third, wood and trees began to heat up. At the fourth, smoke came out of wood and trees. At the fifth, everything got red hot. At the sixth...... At the seventh, the whole land caught fire".
Balor hears a prophecy that he would be killed by his grandson. To avoid his fate, he locks his only daughter, Ethniu, in a tower on Tory Island to keep her from becoming pregnant. One day, Balor steals a magical cow of abundance, the Glas Gaibhnenn, from Goibniu the smith. He takes it to his fortress on Tory Island. Cian, who was guarding the cow for Goibniu, sets out to get it back. With the help of the druidess Biróg and the sea god Manannán, Cian enters the tower and finds Ethniu. They have sex, and she gives birth to three sons. Balor attempts to drown the boys in the sea, but one is saved and is raised as a foster-son by Manannán. He grows up to become Lugh.