I believe it was Flemeth who took control of Solas. Note the eye color change and the smoke emanating much like the smoke when Flemeth appears in the forest. Furthermore, Flemeth apologizes to Solas after Solas apologizes for the events he caused. Flemeth has no reason to apologize other than she knows she is about…

Take a look at the incomplete part of the mural found in the room where Solas once hung out - it looks very much like a wolf snarling above a dragon impaled by a sword (the body of the dragon is stretched out with the wings held straight up...I thought it looked like a leg and a foot at first but that made no sense).

So the main thing I question is.. did Solas lock away/kill Flemeth OR did Flemeth take control of Solas' body as she had "planned" to do with both Morrigan and Kieran? A part of me wants to know more about the Dread Wolf/Solas but also a part of me wants to keep Flemeth and her wickedly played master plan alive.