Everybody knows the story: a king is told his grandson will kill him, so he locks his only daughter in a tower on an island; a man gets to her anyway; the child is smuggled out; the child grows up and kills him. It is the plot of Acrisius and Perseus with Irish names on it, and it is the version of Balor you will find in almost every retelling.
It is also not in Cath Maige Tuired.
What the early text says, and what it does not
The medieval battle-narrative gives Balor a great deal less than the folk tradition does. He is a leader of the Fomorians and the grandfather of Lugh — Lugh's mother Ethniu is his daughter, and the text states the relationship without commenting on it. His eye is described: it was poisoned once by the fumes of a brew his father's druids were making, and afterwards it destroyed whatever it looked at. It stayed shut. Four men lifted the lid with a polished handle passed through it, and only on a battlefield.
That is essentially the whole of the early portrait. No tower, no prophecy, no imprisoned daughter, no smuggled infant.
The tower and the prophecy come from Irish folk tradition, recorded from oral sources in Donegal and elsewhere in the nineteenth century — John O'Donovan collected a full version during the Ordnance Survey work of the 1830s — and from late manuscript tales of Lugh's birth. That does not make them worthless. They are a genuine tradition with real depth, and the folk versions are often better stories than the medieval one. But a page that presents them as ancient mythology, or as evidence of a shared Indo-European inheritance with Greece, is dating them by four hundred to a thousand years too early.
The kill
At the second battle of Mag Tuired, Balor's eye opens and Nuada and Macha fall. Lugh comes at him from an angle, and as the lid is being raised he casts a sling-stone that drives the eye out through the back of Balor's head, so that it lands looking at the Fomorian army behind him and destroys three companies of them.
Later folklore substitutes a red-hot spear or a thrown weapon, and often has Balor ask his grandson to set his severed head on Lugh's own so that the power will pass to him — a trap Lugh avoids by putting it on a rock instead, which splits, or on a tree, which withers. That closing gambit is folk material and is one of the best things in it.
Tory Island
Toraigh, off the Donegal coast, is where the tradition puts him. The island's eastern promontory carries a genuine fort site called Dún Bhaloir, Balor's fort, reachable along a narrow neck of rock with sea on both sides, and the local landscape is thick with names attached to him. The nineteenth-century folklore collected there treats him as a local tyrant with a real address, which is how place-lore normally works: a giant explains a feature, and the feature confirms the giant.
Whether any of it descends from pre-Christian belief about a Fomorian king or grew up around an impressive fortification is not answerable. What is certain is that the association is documented on the island itself, not imported by antiquarians.
The eyelid that has to be propped
Balor is not unique. In the Welsh Culhwch and Olwen, the giant Ysbaddaden Bencawr has eyelids so heavy that servants raise them with forks before he can look at anyone — and, like Balor, he is a father who must die when his daughter is won. Two Celtic-language literatures, no direct textual contact, one very specific image of a lethal or debilitating gaze under a lid that has to be lifted mechanically.
That parallel is worth more than the Perseus comparison, because the Greek and Irish similarity is the loose one — a prophecy, a tower, a grandson — and shared plot skeletons of that kind circulate freely through folktale. The propped eyelid is a distinctive detail, and its appearance on both sides of the Irish Sea is a real datum about the Celtic-language material rather than a coincidence of story shape.
Where the modern readings overreach
Three claims deserve labelling.
- Balor as a drought or blight god, or as a malign sun. The eye's destructive glare invites this, and comparative mythologists of the late nineteenth century reached for it enthusiastically. No text supports it. The eye is poisoned by a chemical accident, not by association with the sky.
- The Fomorians as the demonised pre-Celtic natives of Ireland. A long-standing scholarly theory, now largely abandoned; the Fomorians in the texts are relatives and in-laws of the Tuatha Dé Danann rather than an ethnic substratum.
- Balor as "the Celtic Cyclops". He is one-eyed and enormous, and there the resemblance stops. Polyphemus is a herdsman defeated by a trick with a stake and a false name; Balor is a war-leader killed in a pitched battle by his own descendant.
His clearest modern trace runs through fantasy gaming. When Dungeons & Dragons had to rename its greatest demon after objections over the word "balrog" in the late 1970s, the replacement chosen was balor — so a Donegal giant's name is now attached, in the largest fantasy game in the world, to a whip-and-sword-wielding fire demon with no Irish content whatever. He also recurs in Irish-set fiction and video games as a straightforward dark lord, which is closer to the folk tyrant than to the medieval figure, and either way considerably simpler than a grandfather killed by the child he tried to prevent.
Is Ethniu a villain or a victim in the folk versions?
Neither, consistently. The versions vary a great deal: in some she is entirely passive, in others she recognises the man who reaches her and cooperates, and in a number of tellings she bears triplets of whom only one survives being thrown into the sea — which is how the story explains why Lugh alone exists. Collectors recorded the tale across Donegal, Mayo and the Scottish islands with substantial local variation, so there is no single canonical account to appeal to.
What do his epithets actually mean?
Two are common in the manuscripts. Birugderc means something like "of the piercing gaze", and Balcbéimnech means "of the strong blows" — a straightforwardly martial title that has nothing to do with the eye at all. The familiar English "Balor of the Evil Eye" is a translator's compression, and it maps him onto a live folk belief rather than onto a manuscript phrase: the droch-shúil, the harmful look cast by a person who admires without blessing, was a serious and widespread concern in rural Ireland into living memory, with counter-charms to match. The medieval eye is a weapon; the folk eye is a social hazard, and the epithet slides between them.
Does Balor appear anywhere outside the Irish and Scottish Gaelic material?
No. He has no Welsh counterpart under a related name, no Continental inscription, and no Roman-era attestation. Unlike Lugh, whose name is carved on stones from Spain to Switzerland, Balor exists only in Gaelic literature and folklore — which makes claims about "the ancient Celtic god Balor" doubly misleading, since he is neither ancient in the surviving record nor Celtic beyond one island group.