If the rumors are to be believed, Episode 7 of Game of Thrones might see the return of one thought-to-be-dead character, Sandor Clegane, otherwise known as The Hound. You may remember The Hound as Joffrey's (aka The Worst) head henchman with an apparent soft-spot for Stark daughters. He saved Sansa from a violent molestation, and protected Arya as she journeyed away from King's Landing after her father's beheading. While The Hound can be vicious, his brother Gregor Clegane is a whole other ballgame in terms of evil, and the two do not get along. Why do the brothers Clegane hate each other so much? Well, it started with some childhood squabbling, in which Gregor once shoved Sandor's face into a fire, which would put anybody off.
The characters of Sandor Clegane and Gregor Clegane, or The Hound and The Mountain, respectively, appear at first blush to be quite similar, but later turn out to be foils of one another. While The Hound is loyal above all else, The Mountain is pure violence and evil. He makes Ramsay Bolton look halfway sympathetic. The Hound has killed many times, but always at the orders of the person he serves. He killed the butcher's boy, true, but only under Joffrey's orders. When he was helping Arya, he stopped at nothing to protect her. The Mountain, on the other hand, is famed in Westeros as an indiscriminate murderer and rapist. Much like Ramsay, Gregor Clegane is purely evil.
The brothers' hatred of one another goes deeper than Sandor's first hand experience of Gregor's cruelty. They are constantly at odds because they are one another's intellectual and spiritual opposite, yet they are deeply connected by blood. Season 6 of Game of Thrones has dealt with resurrection and the impermanence of death quite a bit. The Wights and White Walkers, Jon Snow, and The Mountain himself have all been resurrected from the dead. The Hound's return, after he was presumed dead, would fit nicely into the theme of this season.
Fans are already gearing up for a highly anticipated showdown between The Hound and The Mountain, referred to in forums across the internet as "Cleganebowl." So far, it is just a theory, but the possible return of The Hound could mean that it's true. The theory goes that The Hound and The Mountain will have to fight to the death in Cersei Lannister's trial-by-combat. You may recall Cersei mentioning her upcoming trial in Episode 6. She wasn't worried because, of course, her champion will be The Mountain. But maybe fans are right, and The Hound is about to fight his brother. In which case, I'd tell Cersei to be worried.