The secret rites of the druids, carefully shielded from foreigners, have intrigued students of the unknown for centuries. Yet were it not for the curiosity of their Greek and Roman contemporaries, the druids' exotic ministrations might have passed permanently into obscurity. In the 3rd century B.C., Julius Caesar was one of the first to report on the white-robed druids and their sinister activities in remote caves and hidden oak groves. He did not mention Stonehenge, but the druids might have worshiped there, for its construction had already been completed.
As priests of the ancient Celts, who populated much of France and Britain, the druids often functioned as arbiters and judges, settling disputes, passing judgments and assigning penalties. In addition, they were sometimes charged with honoring the gods by sacrifice—mostly animal, but occasionally human—and with controlling the mysterious workings of spirits and souls. The Celts considered the human head the home of the soul; they also believed that the head continued to live even after separation from the body and that it might assist whoever possessed it. A Roman writer, Diodorus, reported that the Celts kept trophy heads in cedar chests and would not part with them even in exchange for their weight in gold. After battles, the heads of heroes and prisoners were spiked on poles for decoration. Heads carved in stone and dried human heads have been found wherever the Celts settled.
Another important druid duty was to appease the spirits of the dead. In particular, the eve of Samain on the final day of October was considered a time of great danger because, as the power of the sun weakened, spirits roamed the earth. Today, Samain's druidic mood of fear and witchery survives as Halloween.
