According to a man quoted all over the internet on this topic, Rowan Moonstone, which I can only assume is a pen name, the Druids help “fire festivals,” days where all of the hearths went dark and then were lit again by holy light, essentially, the dark half of the year and renewal.  You can see his explanations for things here, though I can’t really vouch for his accuracy as none of his sources seem to be primary sources, though, in fairness, those would be hard to find as the ancient Celts were a people with a strong oral tradition, not a strong written one: http://www.featherlessbiped.com/halloween/rowan.htm I don’t know if…