Druids are scholars of the forest, and their understanding of nature's workings is deep. They take in wild animals and help them heal of wounds and sickness, they also take in most anything injured or orphaned. The druids' grove, grown around the Tree of Life, is a sanctuary where no blood is spilled. Leaders of druid circles are known as hierophants, if they are male, and flaminikas, if they are female.
Druid circles and sacred places
The Ghost in the Tree claims to have once been a druidess who had kept watch over the Velen grove until the Crones murdered her and imprisoned her ghost in the tree. Geralt can either let her free or kill her.
In The Witcher computer game
The druids can be found in the druids' grove in the swamp, just north of the lumberjacks' glade in Chapters II and III. In Chapter V, some of them have fled to the swamp cemetery, where the Green March preparations appear to be in full force in the druids' cave.
The druids are caring individuals and have no wish to see anyone or anything suffer. A nice side benefit of this philosophy is that anyone in their immediate vicinity who needs it receives free healing.
The Elder druid is alone among the druids willing to sell and buy things. He is a source of knowledge and the one Geralt is supposed to speak with, mostly, but not exclusively.
The Green March is a peaceful attempt by the druids and like-minded people to draw attention to the preservation of nature.