The North Grove... and Duncan
So if you picked Royland as your Sentinel Duncan is the traitor. This we all know to be true. And it's clear that Duncan has been giving the Whitehills a lot of information on the Forresters.
Do you think he kept his word to keep Gregor's secret or did he spill the beans on the North Grove as well? He said he swore an oath to Gregor, not Ethan or Rodrik (I realize Royland says much the same thing). Would this put his nephew's life in peril? Do you think House Whitehill would do anything about it? I personally doubt it (venturing that far north for what most consider a fairy tale wouldn't be something I think most people would do).
I should mention I don't think he would betray Gregor's final orders for him, but I'm curious what others think.