User Summary: Sourcebook on Spiritualism with historical information, plot hooks and the Medium advanced class.
From the introduction:
Spiritualism is the belief that man can interact with spirits of the dead in order to learn information and improve himself (some Spiritualists, especially Christian Spiritualists, extend this interaction to include supernatural beings such as angels). Practitioners of Spiritualism are generally known as Mediums. As the name implies, a Medium is the conduit through which spirits and other outsiders can interact with the physical world. While this title conjures images of séances in darkened rooms, mediums were considered capable of healing as well as divination.