Hafþór Júlíus Björnsson is the actor best known for playing The Mountain on Game of Thrones. And after being brought back to life by former maester and current mad scientist Qyburn, he's been looking pretty gross under that helmet. It seems like the only one that knows what he looks like under there other than Qyburn is Septa Unella, and it doesn't look like she lived to tell anyone about it. But thankfully for you, Björnsson tweeted a picture of his face. First, here he is with the helmet on:

Sources: Twitter: Hafþór Júlíus Björnsson