Hafthor Bjornsson was cast as Gregor “The Mountain That Rides” Clegane on Game of Thrones for a reason: he’s one of the strongest men in the world. At 6-foot-9 and 400-ish pounds, Bjornsson is certainly a force to be reckoned with.

See what happened when he challenged Devon Larratt, a two-time world arm wrestling champion, to an arm wrestling match: