As I expect you know, standard mainstream Christianity holds that the Devil and his cohorts use channeling to deceive and gain control of people by pretending to be spirits of the deceased. And in the Old Testament there's the story of The Witch Of Endor, who was a medium consulted by King Saul to raise the spirit of Samuel. The Prophet duly appears - and then scolds Saul for having broken the rules by summoning him. Thus, the teaching goes - leave well alone.
Not that I hold to that, but I guess there's a good (non-exclusive?)reason for it. Is Ignorance Bliss? Or was it in fact a good thing that Adam and Eve did eat from The Tree Of Knowledge?