I think it's time the career of Ser Gregor Clegane was re-evaluated. I've heard it suggested that he's a victim of circumstance, but so many of his actions seem like they must be deliberate. But why are Gregor's actions so over-the-top and brutal? Won't they damage Tywin's reputation? We know Gregor was a promising young squire, knighted by Rhaegar himself, so how did he come to be such a monster? The answer is simple: Gregor Clegane is a double agent working for the Tullys to discredit th