Who Were The Druids?

Despite much being written about the Druids, they themselves did not commit anything to writing. Any early written sources were in Greek or Latin writings, the latter were loaded with bias  and propaganda against the people commonly known as Celts.They also appear in later Christian writings

The popular , romanticised portrayal of Druids emerged from the gentleman antiquarians of the C17/C18 and white robed figures at Stonehenge ,Eisteddfods and the Gorseddau in Wales.

The reality probably is that they were politicians, advisors, religious leaders and played a key role in pre- Roman society. It is unlikely that the role of the Druids completely died after the Roman invasion of Anglesey ( Tacitus mentioned 'dark groves' and sacrifices on Anglesey) by Suetonius Paulinus c AD 61.
Druidary remained intact in Ireland for much longer - there was little or no Roman influence there.
St. Columcille/ Columbus is said to have left Ireland for Iona after a battle with the Druid Cahbad in which over 3,000 people were killed. The role of Druids probably became intermingled with Christianity.