'The Mountain' from 'Game of Thrones' takes on a pro arm wrestler

— -- Hafthor Bjornsson is one of the strongest men in the world -- a 6-foot-9, 400-ish-pound behemoth whose unique abilities got him cast as Gregor "The Mountain That Rides" Clegane on "Game of Thrones."

Devon Larratt is a two-time world arm wrestling champion -- and about half Bjornsson's weight.

Here's how it went down when the two of them faced off.

If only Oberyn Martell could see this now.