Even if Gregor Clegane wants to atone for his sins, his malicious nature and utter insolence make his character all but irredeemable. More popularly known as the Mountain on Game of Thrones, Gregor's legacy is filled with suffering, sorrow, and an endless stream of blood.

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Given the close relationship between Houses Lannister and Clegane, it's no surprise that the Mountain is called "Tywin Lannister's Mad Dog." He brutally murders Queen Elia and her children, and goes unpunished for nearly two decades. Sandor finally manages to kill his older brother in Season 8, avenging himself as well as Gregor's victims.

8 The Mountain Maims And Kills People Without A Shred Of Dignity

Gregor's notoriously violent temper is at the heart of his reputation. The Mountain inflicted horrific punishments on his own followers; the Hound states that his brother "once killed a man for snoring." Gregor unleashes his anger on innocent bystanders like Pia, a Harrenhal servant girl, who makes the mistake of interrupting Gregor's "thoughts" and is penalized with a fist to her face.

After losing the Hand of the King's jousting tournament, the Mountain furiously attempts to avenge his defeat by slaying the victor, Ser Loras Tyrell, in full view of the King. Had Sandor not stopped him, Gregor would have almost certainly been executed for this public crime.

7 He Was A Violent Fiend Even As A Young Child

Gregor was apparently monstrous even as a young child, "near six foot tall and muscled like an ox." After discovering his six-year-old brother playing with one of his toys, Gregor "pressed [Sandor's face] to the fire like [he] was a nice, juicy mutton chop."

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The Hound ruefully mentions that their father falsely claimed that Sandor's "bedding caught fire," consequently protecting and enabling Gregor's savage habits. In fact, House Clegane's employees are terrified of being in the Mountain's presence, given several rumors concerning his record of maltreating servants.

6 The Mountain May Have Murdered Many Family Members

Sandor believes he's the only member of House Clegane to have survived his brother's rage-fueled rampages. He can't exactly prove Gregor's role in the suspicious deaths of his father and sister but the Hound's assumption is justified, considering the Mountain's bloodthirst and disregard for familial affection.

In the books, Ned Stark ponders the rumors associated with Gregor Clegane, including "dark whisperings about the deaths of his first two wives." By all accounts, it seems that the Mountain is a classic solipsist: in his eyes, everybody else might as well not as exist.

5 He Subjects Innocent Villagers To His Savagery

Tywin Lannister only hires people who can satisfy his demands, regardless of the methods used to achieve them. Thousands lost their lives and livelihoods, often in horribly violent ways, just so Tywin could maintain his iron grip over the Iron Throne. Hoping to distract and demotivate the North, Tywin tasks his mad dog with wreaking chaos on the Riverlands.

Gregor takes immense pleasure in watching innocent villagers writhe in anguish, displaying a level of cruelty that exceeds the wildest imaginations. Only Euron Greyjoy and Ramsay Bolton are as wantonly malicious as the Mountain.

4 Even Manticore Venom Is Incapable Of Killing Him Instantly

Manticores are some of the most poisonous creatures in Game of Thrones, explaining their popularity among assassins. Barristan Selmy saves Daenerys from death by manticore, thereby earning her undying trust and admiration.

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Although Oberyn suffers a crushing defeat at Gregor's hands, he shrewdly spreads manticore venom on the edges of his spear, diluting its effects in order to prolong the Mountain's agonizing death. Unfortunately for the Red Viper, Gregor manages to stay alive long enough for Qyburn to delay his demise. House Martell might have been avenged if Oberyn had simply used a full dose of manticore venom.

3 The Mountain Is At Least Eight Feet Tall

There are quite a few gigantic characters in Game of Thrones — Jaime Lannister, Stannis Baratheon, Khal Drago, Sandor Clegane, Brienne of Tarth, and Hodor are all well above six feet in height. At a whopping eight feet tall and 400 pounds of pure muscle, the Mountain dwarfs everyone except the Giants.

His inhuman strength is the result of his towering stature, allowing him to wield great swords like they're made of wood. As a testament to his incomparable prowess in combat, Gregor is capable of decapitating "a horse with a single swing of his sword." There are very few people who can successfully defeat the Mountain in a one-on-one fight.

2 Prince Rhaegar Makes The Mountain A Knight

With Robert Baratheon's victory looming on the horizon, Tywin Lannister proactively takes measures to protect the Lannister name. During the Sack of King's Landing, Gregor is ordered to extinguish the Targaryen line by killing Aegon and Rhaenys, both of whom were literal babies at the time.

Their father Rhaeger is defeated and killed before he hears the news, saving him the heartbreak of dealing with his family's murder. Ironically, it is Rhaegar who anoints Gregor as an official Knight of the Seven Kingdoms. This is the point when Sandor loses all faith in the institution of knighthood.

1 His Zombie Form Is Named Ser Robert Strong

When the manticore poisoning puts the Mountain into a coma, Grand Maester Pycelle insists that it's not possible to revive him. Qyburn dismisses his concerns, claiming to have secret medical knowledge based on his secret, abominable experiments. He informs Cersei that "the process may change him, somewhat," but she doesn't mind as long as he retains his strength.

In the books, Qyburn introduces Cersei to a champion warrior who "no living man will be able to withstand." The Mountain's post-mortem zombie form is named Ser Robert Strong, arguably a snide reference to the late King Robert Baratheon.