Second trial by combat of Tyrion Lannister

"Elia Martell! Who gave you the order? Who gave you the order?! Say her name! You raped her! You murdered her! You killed her children! Say it... say her name. Say it!"

- Oberyn Martell demands the Mountain's confession.

The Trial by combat of Tyrion Lannister is an event in the War of the Five Kings. As a result of the farce of a trial Tyrion Lannister is put through, he demands trial by combat to defend his innocence and ruin his father's plans to exile him to the Wall.

Prelude
When King Joffrey Baratheon is poisoned at the feast of his wedding to Margaery Tyrell, he points to his uncle Tyrion Lannister apparently accusing him, as he checks the goblet for poison and he is seized and arrested by members of the Kingsguard on Queen Cersei Lannister's orders.

Tyrion is later put on trial with the newly-crowned King Tommen Baratheon declaring himself unfit to sit in judgement and giving the responsibility to three judges: Tywin Lannister, Hand of the King and Protector of the Realm, as presiding judge, Lord Mace Tyrell of the Reach, and Prince Oberyn Martell of Dorne. Cersei has several witnesses testify against Tyrion, such as Ser Meryn Trant, Grand Maester Pycelle, and Varys. They all give strong (yet circumstantial) evidence of Tyrion's guilt. He seems particularly hurt by Varys's betrayal. After a one hour recess, his brother Jaime comes to Tyrion and tells him that, when the verdict of guilty is pronounced, he must ask for mercy and he will be allowed to join the Night's Watch. Secretly, Jaime had made a deal with Tywin: in exchange for sparing Tyrion, Jaime will renounce his vows and return to Casterly Rock as Tywin's heir. However, Cersei calls in her last witness: Shae. A hurt Tyrion can do little as Shae reveals his sexual pleasures in front of the court and his supposed desire to bed Sansa Stark, which she agreed to let him do if he killed the King for her. Tyrion's anger at the betrayal leads him to lash out: he angrily states that he had saved King's Landing from Stannis Baratheon and that when he saw how all turned on him for killing a king that they all hated, he wished that he had let Stannis kill them all.

​Tywin attempts to silence Tyrion but his son turns on Cersei, declaring that he was innocent of killing him but that he he wished he had. He then turns on Tywin and calls the trial a farce and that it is really a repetition of the trial he had been on since he was born: for the crime of being a dwarf. Not wanting to submit to the "justice" that was being served on him, Tyrion demands a trial by combat.

Cersei appoints Ser Gregor Clegane, the Mountain That Rides, as the Crown's champion. Tyrion first asks his brother Jaime to fight for him, but he refuses, saying that he simply cannot fight like he used to. Tyrion then asks his friend Bronn to be his champion, but he too refuses, arguing that the Mountain is an incredibly dangerous fighter, one that would cost him his life if he makes a single mistake. Finally, Prince Oberyn Martell approaches Tyrion and volunteers to be his champion, as he wants to avenge his sister Elia, whom the Mountain raped and murdered along with killing her children during the Sack of King's Landing.

The Duel
Lannister guardsmen escort Tyrion to a plaza where the combat is to take place, where he finds a large crowd in attendance to watch. He is not impressed to see Oberyn wearing light armour and armed with a spear- in comparison to his opponent, who is clad from head to foot in heavy plate and wielding a greatsword- and is drinking before the fight, but Oberyn dismisses Tyrion's concerns, noting that he always drinks before a fight and favours maneuverability over protection, dismissing his paramour Ellaria Sand's fear that he will lose. After Tywin cuts short a long-winded speech from Pycelle asking the gods to favour the innocent, the combat begins.

Oberyn, after impressing the crowd with some acrobatics, goes on the attack, stabbing out at Gregor and constantly moving out of the knight's reach, forcing him to tire himself out chasing Oberyn. All the while, Oberyn taunts Gregor by constantly bringing up his part in the murder of Elia and her children and demanding a confession, only enraging Clegane further. As the fight progresses, Oberyn manages to seriously injure Gregor, stabbing him first in the chest, severing his hamstring and then burying his spear in Gregor's stomach, pinning him to the floor. As Jaime and Tyrion exchange a relieved grin across the arena, a furious Oberyn circles the prone Gregor, demanding that before he dies, Gregor confess to murdering Elia and her children, and that it was Tywin who gave the order.

However, Oberyn gets too close, and Gregor manages to trip and seize him. Berserk with fury, Gregor roars for all to hear that he raped and killed Elia as he smashes out Oberyn's teeth, gouges out the man's eyes with his thumbs, before crushing Oberyn's skull between his fists. As Ellaria screams in horror and a stunned silence sweeps over the crowd, Tywin gets to his feet and proclaims the will of the gods is clear; Tyrion is guilty and sentenced to death. Tyrion cannot even reply, staring in catatonic astonishment at Oberyn's corpse, as does Jaime; the only different reaction is from Cersei, who smirks triumphantly at the death sentence.

In the books
In the A Song of Ice and Fire novels, the duel occurs very similar to the way it does in the TV series. There are only small differences, such as a stableboy wandering out onto the duel ground because the crowd watching the battle is even larger whose arm is chopped off when Oberyn dodges Gregor and then gets beheaded by the Mountain; and Tyrion vomiting after Oberyn is killed once the reality of his fate hits him.

During the fight, Oberyn, who does wear a light helmet, uses his shield to reflect sunlight into the Mountain's visor and blind him. The Mountain also carries a shield painted with the seven-pointed star of the Faith of the Seven.