Celtic

It is not settled that there was a Celtic pantheon. Several hundred divine names are attested from Gaul and Britain, and the great majority appear once, at one place, often paired with a Roman god in an inscription set up by someone working within Roman conventions. From that material it is difficult to demonstrate a shared organised body of gods rather than a shared style of religion practised locally.

What can be said is that no single sovereign presides. A handful of names recur widely enough to look pan-regional, Lugus and the horse goddess Epona among them, but they do not form a court, and there is no succession narrative from the continental material at all.

The Irish material is much richer and much later, and it is the source of nearly every structure a reader will have seen attributed to the Celts. There the Tuatha De Danann arrive, defeat the Fomorians in battle, hold Ireland, and are in turn displaced by the sons of Mil and retire into the mounds. That is a genuine narrative of divine succession by conflict and settlement. Whether it can be extended to Gaul or to Britain is exactly what scholars disagree about, and the atlas records the claim as debated for that reason.

The pattern that does hold across the whole area is locality. Gods attach to a river, a spring, a hill, a tribe. The divine geography is the real structure, and the pantheon, if there was one, was assembled from it rather than imposed on it.

There is no Celtic scripture and no Celtic mythographer. Every route to this material passes through someone else's hands, and each route distorts in its own direction.

The first is Greek and Roman ethnography, above all Caesar, who describes the gods of Gaul by giving them Roman names and arranging them by function. That passage has shaped every later account, and it tells us at least as much about Roman habits of classification as about Gaulish belief.

The second is epigraphy: dedications carved in the Roman provinces, many of them pairing a native name with a Roman one. These are contemporary and they are evidence of real cult. They are also the product of a period in which Celtic religion was already being reorganised under Roman rule, and they preserve names far more reliably than meanings.

The third is the medieval Irish and Welsh manuscripts, written by Christian scholars centuries after conversion. The Irish material in particular is vast and internally structured, and it is also frankly literary, with the old gods recast as ancient peoples in a pseudo-historical scheme designed to fit Ireland into biblical chronology.

The druids, who might have resolved much of this, taught orally and by policy did not write their doctrine down. Their absence from the record is not an accident of preservation but a decision they made, and it means the tradition's own account of itself was never committed to a surface that could survive.