The most powerful of all Celtic magical creatures, the Dragon represented the whole of creation. As part serpent and part bird, it symbolises the union of the beneficial elements of water and air, of matter and spirit. The fiery breath of the Green Dragon was believed to purify and give new life. To the Celts the dragon was a creature of a parallel world an played an important role in Celtic religion. It is gatekeeper to other worlds, and also a guardian of wealth.
Dragons are also frequently found in churches, both outside, to ward off evil, and inside, often in the company of the Green Man symbol.
Celtic Dragon Jewelry from Amazon.com