POSSIBLE SPOILER!Looking good for my pet theory on who the fox is. In human form he looks sufficiently like Peridot that I doubt this would count as a really major spoiler right now, if I'm right.Peridot is one of three brothers. We know where the older brother is, and Peridot's the younger. This has left a question mark over where the middle brother is since almost the start (So very nicely telegraphed, if I'm right!).I've long suspected Fox is Peridot's middle brother.