Ok, Greg said that the traitor from the first comic-to be revealed in the movie-should be a surprise. So, who better than Raanu?
It was a small being it seems, so it should be Agori or Bone Hunter, but I'm guessing Raanu.
Who knows, what we know of Raanu may be only the tip of the iceberg. Maybe he has an evil side to him...
And no, this isn't a joke assumption or anything. I really am assuming Raanu.