Esta resposta é baseada em A Storm of Sword e A Feast for Crows, por isso conterá spoilers
A luta entre Oberyn e Gregor não fazia parte do plano de Tywin , no entanto, estava fora de seu controle. Como mãe de Joffrey, foi Cersei quem escolheu Gregor como campeão. Além disso, Tywin não sabia que Oberyn seria o voluntário como campeão de Tyrion. Então toda a luta estava fora de suas mãos. Tywin (e todos os outros) ficaram surpresos que Oberyn se ofereceu como campeão de Tyrion. Ninguém pensava que alguém, especialmente um príncipe, se oferecesse para lutar contra a Montanha, particularmente para salvar Tyrion.
[Uma tempestade de espadas: fogo e ouro Spoilers]
It was Mace Tyrell who turned to Tyrion and asked the question. “Do you have a champion to defend your innocence?”
“He does, my lord.” Prince Oberyn of Dorne rose to his feet. “The dwarf has quite convinced me.”
The uproar was deafening. Tyrion took especial pleasure in the sudden doubt he glimpsed in Cersei’s eyes. It took a hundred gold cloaks pounding the butts of their spears against the floor to quiet the throne room again. By then Lord Tywin Lannister had recovered himself. “Let the issue be decided on the morrow,” he declared in iron tones. “I wash my hands of it.” He gave his dwarf son a cold angry look, then strode from the hall, out the king’s door behind the Iron Throne, his brother Kevan at his side.
...
No matter what happened, Tyrion had the satisfaction of knowing that he’d kicked Lord Tywin’s plans to splinters. If Prince Oberyn won, it would further inflame Highgarden against the Dornish; Mace Tyrell would see the man who crippled his son helping the dwarf who almost poisoned his daughter to escape his rightful punishment. And if the Mountain triumphed, Doran Martell might well demand to know why his brother had been served with death instead of the justice Tyrion had promised him. Dorne might crown Myrcella after all. It was almost worth dying to know all the trouble he’d made.
Nós aprendemos antes da luta que Tywin estava planejando mentir para Oberyn, e dizendo que era Amory Lorch, não Gregor, que matou Elia e seus filhos.
[Uma tempestade de espadas: fogo e ouro Spoilers]
“And when Oberyn demands the justice he’s come for?”
“I will tell him that Ser Amory Lorch killed Elia and her children,” Lord Tywin said calmly. “So will you, if he asks.”
“Ser Amory Lorch is dead,” Tyrion said flatly.
“Precisely. Vargo Hoat had Ser Amory torn apart by a bear after the fall of Harrenhal. That ought to be sufficiently grisly to appease even Oberyn Martell.”
“You may call that justice...
“It is justice. It was Ser Amory who brought me the girl’s body, if you must know. He found her hiding under her father’s bed, as if she believed Rhaegar could still protect her. Princess Elia and the babe were in the nursery a floor below.”
“Well, it’s a tale, and Ser Amory’s not like to deny it. What will you tell Oberyn when he asks who gave Lorch his orders?”
“Ser Amory acted on his own in the hope of winning favor from the new king. Robert’s hatred for Rhaegar was scarcely a secret.”
~ Uma tempestade de espadas
No entanto, Tyrion depois revela a verdade para Oberyn (ou parte dela).
[Uma tempestade de espadas: fogo e ouro Spoilers]
“I am not lying. Ser Amory dragged Princess Rhaenys out from under her father’s bed and stabbed her to death. He had some men-at-arms with him, but I do not know their names.” He leaned forward. “It was Ser Gregor Clegane who smashed Prince Aegon’s head against a wall and raped your sister Elia with his blood and brains still on his hands.”
“What is this, now? Truth, from a Lannister?” Oberyn smiled coldly. “Your father gave the commands, yes?”
“No.” He spoke the lie without hesitation, and never stopped to ask himself why he should.
Após a luta entre Gregor e Oberyn, enquanto Gregor está morrendo, e confessou durante a luta, Tywin planeja entregá-lo aos Martells. Ele tenta fazer Pycelle salvá-lo, para que ele possa entregá-lo aos Martells vivos.
[Uma tempestade de espadas: fogo e ouro Spoilers]
“Then I fear Ser Gregor may die.”
“Undoubtedly. I swore as much in the letter I sent to Prince Doran with his brother’s body. But it must be seen to be the sword of the King’s justice that slays him, not a poisoned spear. Heal him.”
No entanto, quando está claro que ele vai morrer, entregar sua cabeça é suficiente.
[Festa de spoilers de corvos]
When he dies, bring me his head. My father promised it to Dorne. Prince Doran would no doubt prefer to kill Gregor himself, but we all must suffer disappointments in this life.
~ Cersei para Qyburn (que está tratando Gregor) em A Feast For Crows
[Festa de spoilers de corvos]
“His long wait is almost done. I am sending Balon Swann to Sunspear, to deliver him the head of Gregor Clegane.” Ser Balon would have another task as well, but that part was best left unsaid.
“Ah.” Ser Harys Swyft fumbled at his funny little beard with thumb and forefinger. “He is dead then? Ser Gregor?”
“I would think so, my lord,” Aurane Waters said dryly. “I am told that removing the head from the body is often mortal.”