"Think of the wishes as magical computer programs," Bella says. "If I wish 'unstick Glory from Ben, put Glory on Mercury', then this will either work or not, but if it works, something I haven't thought of could cause something I don't expect, just like computers don't always behave even though no one expressly programmed in any bugs. That's why I have to think of all the things that might go wrong first. What will Glory be able to do when she's unstuck? How fast will she be able to do it - faster than I can stop her? Are you, in some way you have not chosen to tell me about, attached to her in such a way that you will come to harm in her absence if I don't specifically wish around it? I know some people whose lives are dependent on external souls that are shaped like animals, it would not be the weirdest thing I've heard if your life is in some way dependent on Glory's occupancy and I can probably work around it but I have to know how to be sure."