I'm not sure if this is the case, but didn't Mannimarco ascend to godhood? Him being a God you would assume he would take his followers souls when they die. He might even have claim on human souls trapped in black soul gems. If that were true wouldn't it be plausible that the souls go to him instead of going to the Soul Cairn, they would go to Mannimarco since he, if I'm not mistaken, has a part in creating black soul gems. This seems like it would cause a conflict between him and the Ideal Masters. Since the Soul Cairn takes souls specifically from black soul gems, then couldn't it cause a clash between the Ideal Masters and Mannimarco? That is if Mannimarco has claim on souls from black soul gems.