I really enjoy the hints CS Lewis makes to these ancient people in THAT HIDEOUS STRENGTH. He even called his Merlin character an “old Druid.”Almost everything that we think about "druidry" has been written since the 18th century. The earliest claim to a documented druidic order is 1717, and that one's disputed -- the earliest undisputed claim is 1792.
That is not to say that there are no ancient uses of the word. There are a small handful, but they tell us almost nothing about the referent. Tacitus, writing around AD 61, records a Roman attack on "druids" at Anglesey. But he tells us nothing about them except that they spoke "dreadful imprecations."
The few ancient references lead us to think that they may have been judges and record keepers.
By the 7th century, there were a few "bards" using the term, but whether they had institutional continuity with the group briefly referenced in earlier documents, the historical record does not answer for us.
At any rate, historians are confident that there is no institutional continuity with the orders created in the 18th century.
Although almost everything we think about "druidry" (if that is even an accurate term for anything that existed in antiquity) is conjecture (charitably) -- including whether or not druids were religious figures -- nevertheless we are safe in making some general assumptions about their religious beliefs, since paganism has always been pantheistic and usually taken very similar forms across the world.
A blessed All Saints Day to all.
The little hints he gives of life in old pagan Britain are pretty fascinating and I always wish he’d have elaborated more. He was a studied medievalist and could surely talk all day about little details that most of us interested in human history would have very much enjoyed.
But some of the hints he gave at old practices were enough to chill the blood a bit (e.g. folk mixing babies blood in the mortar of their houses to stave off evil spirits). He alluded to little overgrown mossy places with kings no one has ever heard of, eyes peering out of the dank darkness, etc. Quite eery and fascinating at the same time. All very “wild” in the original sense.