I'm on my 3rd playthrough now and I am starting to think that Morrigan and Flemmeth are the same consciousness at the same time. We don't know how the possession works exactly so it could be possible that when transferring from the older body to the younger one 'flemmeth: the witch of the wilds' consciousness can inhabit 2 bodies at the same time. On my second playthrough I purposely did not give Morrigan the grimores. She still came to my bedroom and offered me the way out, I asked her how she knew of this ritual and she said she had always known and that it had been part of Flemmeths plan from the very start. On my 3rd playthrough I gave Morrigan the 1st grimore then went to Flemmeth and asked her for the 2nd grimore, gave it to Morrigan and I did not tell her Flemmeth was alive. Then I went back to Flemmeth and her dialogue makes you either choose to kill her or walk away, walking away wouldn't be much fun so I killed her, maybe this is part of her plan also? Maybe in the possession 'flemmeth: the witch of the wilds' can only inhabit 2 bodies at a time and as Flemmeth isn't going to die naturally anytime soon she needs the Flemmeth body to be killed so she can inhabit the 'god child' body. My thoughts on the 'god child' are that it's not going to be a good thing, Morrigan lies to you by saying the old god will be untainted as it's the taint in the baby that attracts the god spirit in the first place, add to that the possibilty of 'the witch of the wilds' possessing the child you have - (Old God + Taint) + (witch of the wilds) = o_O