The Mountain and the Viper

"The Mountain and the Viper" is the eighth episode of the fourth season of HBO's acclaimed fantasy television series "Game of Thrones", and the 38th overall. The episode was written by series co-creators David Benioff and D. B. Weiss, and directed by Alex Graves. It aired on June 1, 2014.
This episode marks the final appearance of Pedro Pascal (Oberyn Martell). The title refers to the duel at the end, between Prince Oberyn and The Mountain.
Plot.
At the Wall.
Mole's Town is sacked by the wildlings, but Ygritte spares Gilly and her son. When news reaches Castle Black, Sam fears for Gilly; Pyp and Edd reassure him that Gilly has survived worse and may yet be alive.
At Moat Cailin.
Reek, assuming his previous identity as Theon, enters Moat Cailin and convinces the occupying Ironborn to surrender in return for safe passage home. However, Ramsay reneges on his offer and has the Ironborn garrison flayed. As a reward for retaking the Moat, Roose presents Ramsay with a decree of legitimization as a Bolton. The Boltons depart for their new seat at Winterfell.
In Meereen.
Missandei sees Grey Worm watching her bathe and covers herself up, but later tells him that she is not offended and laments his castration. Grey Worm, however, notes that if he had not become an Unsullied they would have never met.
Barristan receives a letter with the Hand of the King's seal - Jorah's royal pardon from Robert Baratheon for spying on Daenerys. Jorah is forced to admit his treachery and Daenerys exiles him from Meereen.
In the Vale.
Petyr is interrogated by the nobility of the Vale about Lysa's death, who are skeptical of his claim that she committed suicide. Sansa is asked to testify; she reveals her identity, corroborates Petyr's story and convinces the Vale nobility of his innocence. Petyr, Sansa and Robin leave the Eyrie to tour the Vale.
Sandor and Arya arrive at the Bloody Gate, only to be informed of Lysa's death.
In King's Landing.
Tyrion's trial by combat begins. Oberyn gains the upper hands and knocks Gregor to the ground, but instead of killing him, Oberyn screams at him to confess that Tywin gave him the order to kill Elia and her children. Gregor takes advantage of his distraction to knock Oberyn down, and confesses to the murder of Elia and her children while crushing Oberyn's skull with his hands. Tywin sentences Tyrion to death for regicide.
Production.
Writing.
This episode contains content from three of George Martin's novels: "A Storm of Swords", chapters Daenerys V, Daenerys VI, and Tyrion X; "A Feast for Crows", chapters Alayne I and Alayne II; and "A Dance with Dragons", chapter Reek II.
Reception.
Ratings.
"The Mountain and the Viper" was watched by an estimated 7.17 million people during its first airing. In the United Kingdom, the episode was viewed by 1.811 million viewers, making it the highest-rated broadcast that week. It also received 0.062 million timeshift viewers.
Critical reception.
The episode received high praise from critics and audiences alike, with the fight between Prince Oberyn and the Mountain being hailed as the episode's highlight. On Rotten Tomatoes it obtained a 97% score, based on 32 reviews, with an average rating of 9/10. The website's critical consensus reads, "With one of the most gruesome scenes to date, 'The Mountain and the Viper' delivers a tense, twisty final scene well worth the wait."
Writing for "The A.V. Club", Emily VanDerWerff gave the episode an A- and praised the staging of the final fight by director Alex Graves. Erik Adams, also writing for the "A.V. Club" gave the episode an A. Terri Schwartz, writing for Zap2it.com, wrote the episode was "one of the strongest "Game of Thrones" episodes to date, and that's just the type of episode that the death of Oberyn Martell deserves."