We saw Ser Gregor fall in Season 4–or did we?
Previously on Game of Thrones: To determine the guilt of Tyrion Lannister in the brutal (and frankly very gross) poisoning of Joffrey Baratheon, it is decided that a trial by combat will occur. Tyrion taps the flirtatious Oberyn Martell, while mother of the deceased Cersei Lannister chooses the above-mentioned Ser Gregor Clegane.
After a long struggle in which both men were wounded–and Oberyn lost his life when his opponent crushed his skull–Ser Gregor Clegane was seemingly done in by the Dornishman’s poison-tipped spear. But, thanks to a maester fallen from his peers’ graces and the persistence of Cersei, the Mountain may have found new life.
Undead or Just Dead?
It’s been confirmed that the hulking mass beneath that glinting armor is, in fact, what was once called Ser Gregor Clegane. Cersei goes so far as to reveal this fact to Ellaria Sand. The now-Queen of Westeros is openly quite pleased (and very smug) that the killer of Ellaria’s lover–Oberyn–remains alive and well despite his unfortunate poisoning, while Oberyn remains well and truly gone and dead. While the books haven’t exactly made it explicitly known that the beastly man known as The Mountain is Gregor Clegane, it’s heavily implied, with many eagle-eyed readers picking up on the Mountain’s identity quite early on.
Given all the hubbub about all the ice zombies marching down from the north, it’s not entirely impossible that Ser Gregor, too, is undead. Perhaps Maester Qyburn figured out how to manufacture White Walkers himself? What’s more likely is that he’s keeping the eldest Clegane animate by more sinister means. What is certain is that whatever remains of Ser Gregor Clegane may be the most dangerous being in all of Westeros, capable of crushing skulls like walnuts and inflicting unspeakable violence.