Note: MJ, I'm doing better now, so unless you really want to you don't need to reply to my email.
Let us consider a discrepancy in Multiverser rules and the world of fiction. In 'Angel' on TV, Fred the Genius Girl is sacrificed and her soul is 'burnt up in the fires of ressurection' to make Illria, the Greatest of the Ancient Demons come back. In one of David Weber's stories an evil magic sword has a sacrificed and broken and damaged soul trapped in it. In Ringo's pretty good 'Princess of Wands' about a Southern Baptist soccer mom demon hunter if you die facing off against a demon it gets your soul. There are questions as to whether you might be freed at the end of time.
However, in Multiverser it clearly states that the Anarch powers have no ability to confine an Alliance soul.
I like Multiverser's stance. I think of Ringo's idea as one of the flaws in his rather neat book.
There are also stories about souls trapped as ghosts until some evil spell is lifted, or until justice is done.
One of the theories of ghosts offers a way of resolving this. It says that ghosts are not sentient spirits, but memories embodied in matter.
I had come up with an exceedingly cool end to a book I've never finished. The villainess is a well-meaning sort tormented by guilt which drives her to her villainy, and while she asked for forgiveness, she didn't believe she had received it. She believed enough to ask, which was enough, but not enough to put her guilt behind her. In the end, the hero is triumpant, and she's dead. She waits in the Gray Plains to be picked up by her god, and she is covered in shackles. Her god shows up to take her to Paradise, but she refuses because of her sins. So he reaches into her her mind, removes all her memories, and stuffs them into his pocket with the thought that he might return them to her in ten thousand years when she is stronger. She then happy like a little girl skips to join him.
Thus perhaps the answer is in part 'memories'.