There's Still Hope For These Dead Game of Thrones Characters — in the Books

How he dies on the show: Ser Barristan is fatally stabbed several times during a terrorist raid by the Sons of the Harpy in season five.

Where he's last seen in the books: After Daenerys flees Mereen with Drogon, Ser Barristan takes on the role of Hand of the Queen and conspires to take down Hizdahr zo Loraq (who is also still alive in the books and eager to assume Dany's power).