What character is initially introduced in 1996's "A Game of Thrones is played by Hafþór Júlíus "Thor" Björnsson ?
Hafþór Júlíus Björnsson: Hafþór Júlíus "Thor" Björnsson (] ; also Hafthor Julius Bjornsson, born November 26, 1988) is an Icelandic professional strongman, actor, and former professional basketball player. Hafþór Júlíus Björnsson:  He plays Ser Gregor "The Mountain" Clegane in the HBO series "Game of Thrones". Gregor Clegane:  In the books, the character is initially introduced in 1996's "A Game of Thrones".
Gregor "The Mountain" Clegane