BAL-or
The Fomorian king whose single deadly eye can destroy an army, killed by his own grandson Lugh at the Second Battle of Moytura.
Balor of the Evil Eye leads the Fomorians as their king, and carries a single great eye that was closed from birth and only opened — by several attendants prying back its lid — on the battlefield, where its gaze alone kills or withers whatever it falls on. A prophecy holds that Balor will be killed by his own grandson, so he imprisons his daughter to prevent her ever bearing a child — a plan that fails when Lugh is conceived regardless and later raised in secret.
At the Second Battle of Moytura, Lugh confronts Balor as his eye is being forced open, and drives a sling-stone through it and out the back of his head, turning the deadly gaze back on the Fomorian ranks behind him and breaking their army. Balor's death by his own grandson's hand is one of the best-known fulfilled prophecies in the whole mythology.