MangoFox says: The magic that brings the creatures to Vulpine clearly has something to do with sleep. Might dreaming by chance have anything to do with it? As in, could dreaming prevent the consciousness transfer? Or maybe enable it, so that only a dreaming creature could be summoned?
Robin says: This is a little spoilery, but I’ll tell you! The summoning magic was not strong enough, in this context, to bring an entire being — body and spirit — all the way to Vulpine. It had to settle for one or the other, and the easiest way to deal with the situation in that case was to summon the spirits and create new bodies for them out of the elements at hand (i.e. there on Vulpine).
Because of this, it had to summon those spirits at a time when they were most accessible: when the bodies were asleep. So, no, dreaming has no effect on the magic. And if there are people out there of any species that doesn’t sleep, they’re pretty well exempt from the effects of this magic; lucky them!