"The Mountain and the Viper" is the eighth episode of the fourth season of HBO's medieval fantasy television series Game of Thrones.

[2] In the episode, Mole's Town is attacked by wildlings, but Gilly is spared by Ygritte; Theon Greyjoy negotiates with the remaining ironborn at Moat Cailin; Roose Bolton legitimizes his bastard son Ramsay; Petyr "Littlefinger" Baelish is interrogated by the Lords of the Vale following Lysa Arryn's death; Sandor Clegane and Arya Stark arrive at the Eyrie; Jorah Mormont admits to Daenerys Targaryen that he spied on her for Robert Baratheon years earlier, and is banished from Meereen; and Tyrion Lannister's trial by combat takes place in King's Landing.

The title refers to Tyrion's trial by combat, a duel between Gregor "The Mountain" Clegane and Oberyn "The Viper" Martell.

[3] The episode achieved a viewership of 7.17 million in the United States during its initial broadcast,[4] and received positive reviews from critics, who gave heavy praise to the climactic duel sequence in particular.

Reek, assuming his previous identity as Theon, enters Moat Cailin and convinces the occupying ironborn to surrender in return for safe passage home.

Oberyn quickly gains the upper hand and fatally stabs Gregor with his poison-laced spear, before demanding he confess to killing Elia.

Gregor trips him and, using the last of his strength, confesses to Elia's murder before gouging Oberyn's eyes out and crushing his skull, killing him instantly.

Club, Emily VanDerWerff gave the episode an A− and praised the staging of the final fight by director Alex Graves.