From Druid Magic, by Maya Magee Sutton and Nicholas R. Mann, Llewllyn 2000.
The Druids were the wise men and women of the Celtic peoples. So before we describe the Druids let us describe the Celts.
From about 1800 BCE on, a new cultural impulse flowed across northern Europe. It descended from Indo-European roots, and brought with it new technologies especially in metal-working. Its people spoke the family of languages known as ‘Celtic.’ By the first millennium BCE (the Iron Age), this culture dominated central and western Europe. The evidence suggests that this domination did not occur forcibly, but by a process of slow assimilation with the earlier peoples. It is likely that the older Native European Tradition in its shamanic form continued in an unbroken line into this, the Celtic period.
A specifically "Celtic" style appeared in central Europe as early as 1200 BCE with the advent of the Hallstatt Culture. The development of this culture was influenced by the control of trade routes. This culture declined after 600 BCE, but there arose from it a new and vigorous impulse known as La Tène. These peoples, composed of many different tribes, had contacts with the raw material hungry Mediterranean world. Through this trade they became wealthy and populations expanded. By 400 BCE large groups were migrating east and southwards. Celtic Gauls sacked Rome in 390 BCE, while other tribes moved eastwards, occupied the Danube area and threatened Greece. In the third century BCE, Celtic culture was at its peak. Although still extremely diverse, the many tribes shared the exquisite artistic traditions of La Tène. They possessed a similar social structure, they were able to understand each other, and an immense wealth flowed between them in the form of ideas, stories, myths, laws, values, wine, weapons and trade goods.
By the fourth and third centuries BCE, urban centers and social stratification increased. Charismatic men, and sometimes women, gained power through control of trade and resources with the support of a warrior elite. Some of these centres verged on statehood, with cities, ”national“ boundaries and sanctuaries, nobility and kings, and several classes of subjects. The wise men and women comprised one of these classes. They gathered around the halls of the aristocracy to supply their needs. Their functions included entertainment and genealogy – music, songs, the telling of stories and poems, especially those that praised the exploits of the ruler and his warriors. They provided the old shamanic functions such as herbalism, healing, divination, sooth-saying, and dream-interpretation, but took them in a new direction to serve the needs of the more complex society. These people were the Druids.
By the end of the first century BCE, Celtic society was crumbling before the power of Rome. Resistance in Gaul was at an end, and Julius Caesar had already launched the first invasion of Britain. With the second, Claudian invasion of Britain, the Druids were singled out and massacred. The Romans deliberately undermined Druid leadership and power among the conquered Celtic peoples. But in the long occupation of Britain that followed, 43 – 410 CE, local Celtic practices merged with Roman to produce a synthesis that did maintain many ancient customs – they were both, after all, pagan.
Pressure from the east finally ended both the Roman Empire and Celtic society. Nomadic tribes from the Caucasian steppes invaded Europe in the fourth century CE, and lack of space forced the Germanic and Scandinavian peoples west. The Angles, Jutes and Saxons defeated the newly independent Celts of Britain, and drove them into Wales, Brittany and the never-defeated Celtic fastnesses of Ireland, Scotland and the Isles. It is unlikely that the Druids ever staged a comeback at this time. The tales of King Arthur and Merlin represent what might have been if the Celts had been successful in defeating the Northmen. Christianity followed hard upon the heels of the Germanic invaders, and challenged any remaining Druids. Druid Brehon law however prevailed in Ireland until the Cromwellian invasions. These forces irrevocably changed the face of Celtic culture forever.
In summary, ‘Celts’ was the name given to the European tribes north of the Mediterranean by the Greeks and Romans. This covered an extremely diverse group of peoples none of whom called themselves by this name. ‘Celtic’ was adopted by linguists to refer to the family of languages of Indo-European origin spoken across a broad area of Europe and introduced there from as early as 2000 BCE. ‘Celtic’ was later used by historians to describe the cultural impulse that began in central Europe (Hallstat) before 1000 BCE, and achieved its full flowering with the La Tène era after about 500 BCE. This culture (with the virtue of combining all the above definitions) developed towns, and a highly centralized, hierarchical and socially stratified society. Its features included classes of nobles, priests, warriors, craftsmen and farmers, characteristic of its Indo-European origins. Growth depended upon trade with the Mediterranean world, and for many centuries the Graeco-Roman world mirrored the Celtic and vice-versa. The Druid class grew in response to these social developments and, like the priests of Etruria and Rome, largely served the warrior class and nobles.
Since the conquest by Rome, Celtic or Gaelic-speaking culture only remained on the northern and western fringes of Europe, but has had an enormous effect on the Western world, especially in North America. This is the Celtic diaspora, a rich and varied culture that is giving rise to Druidry again today.