It was a scene, and a story, told in one man's eyes.
In the span of one four-minute scene, we learned more about Tyrion's back story, and his relationship to his family (especially with his sister, Cercei) than we ever learned over the course of nearly four seasons of "Game of Thrones." We also learned how noble, eloquent, inspiring, and (dare I say) caring, Oberyn Martell really is.
Before this episode, I had my mind set that the two champions that would be chosen to fight for the judgment of Tyrion would be Bronn (chosen by Tyrion himself) and Jaimie Lannister (chosen by their father, Tywin). The stones were set in previous episodes for this to be a very possible choice, with much drama that could be mined from such a match-up. Would Jaimie kill Tyrion's champion, a man he just happened to be a sparring partner with, or would he sacrifice himself to allow freedom to his ridiculed, tormented imp of a brother? I was actually looking forward to this possibility - I think any writer would have salivated at the thought of what noble act (or devious act) certain characters in this show could devise from such a set-up, but the choices that (seemingly) were made became somehow far more rewarding.
We learned that Gregor Clegane, "The Mountain", is chosen by Cercei to be the champion against her brother's chosen champion. The Mountain is a behemoth of a man, one that Bronn was too intelligent to fight (having declined the opportunity as champion once more for Tyrion, due to other soon-to-be-wedded obligations), as was Jaimie when asked by Tyrion early in the episode.
Upon the two declinations of champion, Tyrion was not his typical witty self. He was indeed a man of smart words, but there was an understanding to his voice that forgave both Jaimie and Bronn for not accepting. He did not despise them, nor did he beg them. He gave them promises, but nothing more. He reminded me a bit in nobility of Mel Gibson's portrayal of William Wallace in "Braveheart". When offered a liquid to ease his suffering, Wallace declined, stating that taking such a potion would "numb his wits." As with Tyrion, his straight-forward attitude only made more harrowing his words in court from the previous episode. He has accepted his fate, and is almost taking everything else as just a hopeful cherry on top.
When Oberyn entered Tyrion's cell near the end of the episode, the setting was much the same as with Ned Stark's (Sean Bean) final episode in Season One: Dark, moody, with a foreboding presence of doom.
Oberyn sits, and gives the most disheartening story of his and Tyrion's first encounter, when Tyrion was but a baby and Oberyn was but a young boy. He tells Tyrion of the words he was referred by as a child - essentially, the "demon baby" with claws, a tail, and red eyes. Tyrion hears these words, and that they were spoken by both his sister AND his father, and the pain was all but too apparent upon his face. Masterful acting on Peter Dinklage's part - emotional, yet with a certain strength that only a person of his ridiculed nature could ever adhere to.
Then, in one moment, not only is a scene told, but an entire story of a character is told through a single camera shot, held on Peter Dinklage's face as he's told by Oberyn that he was not the monster his family had led people to believe. He may have been a bit misshapen in size, but he was just a little boy. A human boy. And his sister treated him with hate and disdain that only a heartless bitch could ever do.
The tears in Dinklage's eyes become less shed from pain and torment, but of inspiration and enlightenment. They told a story of sorrowful discovery, and yet at the next moment, of heart-filled enchantment.
Oberyn says he wants justice, and all the people he knows of who could give him that justice for the wrongs committed against his family are right there in King's Landing. Tyrion tells him that he has come to the wrong place for justice. Then, in probably my second favorite moment from this season, Oberyn declares that his justice begins with The Mountain - the man who murdered Oberyn's sister. In this, Oberyn chooses himself to be Tyrion's champion.
Masterful writing on both the television show's writers David Benioff and D.B. Weiss, and of George R.R. Martin for not choosing the obvious Bronn/Jaimie angle (if indeed this was the same as was in the novels). And even more masterful acting by both Peter Dinklage and Pedro Pascal. Pascal was able to underline and define both his and Dinklage's characters in one speech, and give the light of gravitas that some writers, directors, and actors could spend a lifetime of film making and never achieve.