We should be careful of names and labels and even more so of preconceived notions and images layed down in our minds from the fictional world as unhelpful fantasies. Imo any diverse society like such as that of the celts would have certainly had a central group of religious leaders, storytellers, teachers and healers- these we call the druids, this name translates as 'oak' , I dont find anything overly fanciful or doubtful about who this group were, just only find it amazing !. They probably used alchemy and what we would describe today as trickery, to shock and awe the people .. some things never change !