The Druids were priests in ancient Celtic society who were responsible for religious rituals and acted as teachers, doctors, lawyers, and astronomers. They were divided into groups focused on religious worship, storytelling, and divination. Druids underwent 20 years of study with other Druids, learning poetry, philosophy, astronomy, and Celtic lore. Their religious ceremonies centered around natural elements and sacrifice, though human sacrifice was rare. As priests, Druids held significant political power and privileges in Celtic communities.