Who is Ambres from Out on a Limb and what is their importance?

Ambres is the spirit that Sture Johanssen channels. He speaks in an ancient form of Swedish, and when Shirley meets him, she is struck by how different his voice is from Sture's voice. Ambres speaks about spirituality and the creation of life when Shirley is in his presence, and she is overwhelmed by his knowledge..... convinced that Sture cannot be faking Ambres' presence.