Question: Hafþór Júlíus "Thor" Björnsson, is an Icelandic professional strongman, actor, and former professional basketball player, he plays which fictional character in the "A Song of Ice and Fire" series of fantasy novels by American author George R. R. Martin, and its television adaptation "Game of Thrones"?
Sentence (from "Gregor Clegane"): In the books, the character is initially introduced in 1996's "A Game of Thrones".
Relevant evidence: No