King Joffrey Baratheon was dead, and you were accused of murdering him. As a result, you were trialed for your crimes, with Tywin Lannsiter, Lord Mace and Prince Oberyn as judges.

You knew that the only way for you to prove your innocence was to demand a trial by combat, so that your case can be judged by the gods.

Several days after you demanded a trial by combat, Oberyn Martell visited you in the dungeons. He offered his services as your champion in the upcoming trial, mainly because he wanted to take revenge on Gregor Clegane for murdering his sister.

"I want to bring those who have wronged me to justice, and all those who have wronged me are right here. I will begin with Ser Gregor Clegane, who killed my sister's children and then raped her with their blood still on his hands before killing her too. I will be your champion."