An illustrated guide to the myths and legends of the Celtic people.   From around 750 BCE to 12 BCE, the Celts were the most powerful people in central and northern Europe. With the expansion of the Roman Empire and the later Christianization of these lands, they were pushed to the fringes of northwestern Spain, France, and the British Isles. But there the mythology of these peoples held strong. The tales from Celtic myth were noted down and absorbed into other cultures. From