Sandor Clegane is Gregor Clegane’s brother. He is Joffrey’s personal bodyguard, and when Joffrey becomes king, he promotes Sandor to the Kingsguard (a group charged with protecting the king). Sandor shares a vulnerable moment with Sansa when he tells her about being terrorized by Gregor as a child. He follows up that vulnerability by threatening to kill Sansa if she tells anyone what he told her.