The 5th season of Game of Thrones, premiering in the spring of 2015, ends with "Mother's Mercy", which landmark episode in total?
Mother's Mercy: "Mother's Mercy" is the tenth and final episode of the fifth season of HBO's fantasy television series "Game of Thrones", and the 50th overall. Game of Thrones (season 5):  The season primarily adapts material from "A Feast for Crows" and "A Dance with Dragons", the fourth and fifth novels in George R. R. Martin's "A Song of Ice and Fire" series, though it also uses elements from the third novel, "A Storm of Swords", as well as the upcoming sixth novel "The Winds of Winter".
50th