Sadly we only have the accounts of his enemies to tell us about Broichan, the Druid of King Bridei of the Picts, who lived in the time of Saint Columba (521-597).
The only mention of the Druid is in Adomnan’s Life of Saint Columba, a highly fanciful and chronologically scattered account of the Irish saint. The first mention of Broichan is in Chapter 34 of Book II of the Life, which mentions a visit by Columba to the Pictish capital of Inverness.