RJ's statement that Taim isn't Demadred doesn't rule out the possibility that Demadred is someone in Taim's inner circle and that Demadred turned Taim to the Shadow by either feeding his jealousy, the 13x13 method, or some other method using either the One or True Powers.
Profile: Mazrim "Don't Call Me Tame" Taim
in Theory Blog
Posted
Another option:
RJ's statement that Taim isn't Demadred doesn't rule out the possibility that Demadred is someone in Taim's inner circle and that Demadred turned Taim to the Shadow by either feeding his jealousy, the 13x13 method, or some other method using either the One or True Powers.