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

Sture Johanssen is a trance medium in Stockholm. Sture is a carpenter before he begins channeling a man named Ambres. Sture makes it his life's work to allow people to speak with Ambres, believing that it is important for people to learn all they can about what Ambres has to tell them. As a result, people help support Sture and his wife with donations when they come to a reading, casting some doubt on Sture's gift.