Wow, I didnt realise this, you are right. Now, things are getting interesting. Damn, this is is rough, the shapeshifter could be anybody... But maybe the 1st character I would point out to is the witch, because in the end we dont know her motivations either. Then again since she is a witch, it could be obvious to blame her... Mmm... Any other shaddy characters xD?
It would explain why she has 2 appearences and her tricky nature (because she definetively knows something else that she is not telling us). But, as a shapeshifter, being isolated in the middle of the swamp doing what exactly?
From my point of view, I think the shapeshifters have a goal and a leader, since they are working together and seems to have the same interests in Northcrest royalty.
In my opinion, the shapeshifter or is someone from Bareshade, or is someone close and related to Northcrest in some way.