Who were the ancient Druids?
The most honest answer to this question is “nobody really knows.” According to the very sparse surviving sources, they were a sacred caste among the Celtic tribes of Britain, Ireland, and Gaul (modern France) in ancient times. Some sources call them philosophers, others call them wizards; nobody actually calls them priests, though this is the most popular interpretation among scholars nowadays. They had traditions, passed on by oral transmission, that dealt with theology, astronomy, divination, and other matters, but essentially all of this was lost with the coming of Christianity. Plenty of books have been written about what the ancient Druids were or were not, but they’re pretty much speculation based on a few fragmentary references in Greek, Latin, and medieval Irish writings.