The Mountain and the Viper (Season 4, Episode 8)

"The Mountain and the Viper" is the eighth episode of the fourth season of HBO's fantasy television series Game of Thrones, and the 38th overall. The episode was written by series co-creators David Benioff and D. B. Weiss,[1] and directed by Alex Graves.[2] It aired on June 1, 2014.[3]

This episode marks the final appearance of Pedro Pascal (Oberyn Martell).

https://en.wikipedia.org/wiki/The_Mountain_and_the_Viper