In Irish mythology, Balor (Balar, Bolar) of the Evil Eye was a king of the Fomorians, a race of giants.
His father was Buarainech and his wife was Cethlenn. According to legend, he lived on Tory Island.

Balor was notable for his one eye, which could kill anyone it looked upon.
He gained this power as a child when watching his father's druids preparing poisonous spells,
the fumes of which rose into his eye. His eye was normally kept closed,
only to be opened on the battlefield by four men using a handle fitted to his eyelid, or, in some versions,
a system of ropes and pulleys.

According to prophecy, Balor was to be killed by his grandson.
To avoid his fate, he locked his daughter, Ethlinn, in a tower made of crystal to keep her from becoming pregnant.
However, Cian, one of the Tuatha Dé Danann, with the help of the druidess Birog, managed to enter the tower.
She gave birth to triplets by him, but Balor threw them into the ocean.
Birog saved one, Lugh, and gave him to Manannan mac Lir, who became his foster father.
He was called Lugh Lamhfada and became a member of the Tuatha Dé Danann.

Lugh led the Tuatha in the second Battle of Magh Tuiredh against the Fomorians.
Ogma disarmed Balor during this battle, but Balor killed Nuada with his eye.
Lugh shot a sling-stone which drove Balor's eye out the back of his head,
where it continued to wreak its deadly power on the Fomorian army.
In other versions Lugh blinded Balor with a spear made by Goibniu,
or decapitated him and used his eye against the Fomorians.

One legend tells that, when Balor was slain by Lugh, Balor's eye was still open when he fell face first into the ground.
Thus his deadly eye beam burned a hole into the earth. Long after,
the hole filled with water and became a lake which is now known as Loch na Suil,
or "Lake of the Eye", which is to be found in County Sligo.