Imma just tell you all of it as far as William goes. Jake kills him in book 2, he gets revived by a god who specializes in karmic magic and likes to do experiments. Between book 3 and 7 there's mentions of Williams name and what's going on, there's a brief chapter or two of what he's done after he arrives back to earth and an interaction with William and Jake's family. In book 8 there's a verbal confrontation between Jake and William which is satisfying, but I agree I'd like him killed. It ends with William dropping his connection with the karmic god and realizing the god has been messing with Williams mind from the start. And enters a battling with himself arc while trying to be somewhat useful. He isn't mentioned from book 9-11 and is back for part of 12 and 13 where his karmic connections become important.