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 any other branch of Christianity does this, but for me, this brought the Pascha service to mind. On the night of Easter, Orthodox pray, sing, and carry candles. Before midnight (though the timing depends often on the parish and how strict they are with traditions), all sources of light are extinguished in the church. This is to represent the tomb and death. At midnight, the priest comes out from behind the gates, faces the parish, and sings, “Come receive the light from the Light that is never overtaken by night, and glorify Christ, who is risen from the dead.” Every candle in the church is lit from the priest’s candle. Then we, as Orthodox Christians, share a meal together in celebration and try to carry the still-lit candles home with us to bring the Light of Christ into the centre of our houses and to remind us of who we were meant to be. In every parish I’ve ever been to, Pascha is standing-room only, even if you only have 15 people there on a regular Sunday. This tells me that the service touches people’s hearts in a unique way. After Pascha, we have Bright Week, a week of celebration and joy. Here is a video of that part of the service so that you have a visual if you don’t know what I’m talking about:
If you watched the video, you’ll see that light spreads throughout the church gradually, just like Christianity spread throughout the world gradually. It may not be everyone’s cup of tea, but it makes me smile. The same line is echoed by the chanters and the parishoners, by the way, “Come receive the light from the Light that is never overtaken by night, and glorify Christ, who is risen from the dead.”
Throughout the ages, humans have represented death as darkness and light as life. Death is what makes us human. In Christian terms, it is the result of sin. According to the Celts it was how the gods created us and our imperfection is what makes us both vulnerable and strong of will. To me, the pagans doing this ties them more to us, not separates them from us. It means that we have certain symbologies (not sure if that’s a word, but if not, it should be) in common.
Here is a video done by a guy who is clearly Russian Orthodox about death as a result of sin and eternal life through the sacrifice of Christ.