Whilst the last series of Game of Thrones has just ended Cersei Lannister's henchman was killed off in the penultimate episode of the season. Although he's one of the show's most popular characters, he earned himself a fair few enemies when he executed fan favourite Missandei.Thor Bjornsson, who plays his character perfectly, is also the strongest man in the world (but you already knew that). On his Instagram account, he decided to challenge his fans a little by starting a challenge. In the video he posted, we see the Icelandic man perform 8 repetitions of shoulder presses with two 60-kilogram dumbbells."I challenge you to do the same with 60-kilo dumbbells," The Mountain wrote in his post. So you now know what you have to do. As for Thor Bjornsson, he'll be back from June 13 to 16 to defend his strongest man in the world title.Check out the video above to see The Mountain's challenge for yourself!