Ok guys, I SOLVED THIS ONE…………………. Think outside the box a bit.. This is some heavy karma stuff here, not easy to interpret at all.. This is HODOR all over.. ok, lets start So, Arya wont do it, the Hound wont do it. Brothers Clegane both know that - They have known it for a very long time. Lets start from the beginning. The Mountain supposedly burned Hounds face because of same non important brother grudge, but that’s not the truth.. Hound has always had the gift of foresight only till recently he had denied it .. why ? He was afraid. The cause is a childhood trauma. Too early he started to experiment with this gift and he has seen some heavy stuff there that he wasn’t ready to see…..

One of the things was the manner of his brothers death, which is not nice at all. He unwisely shared this info with his bro which messed up Gregors head totaly. The Mountain was not always evil, its this revelation that made him..

Now we go into the realm of real guesswork !!! Major spoiler ahead. Gregor is going to be killed buy the undead (or in some way related to their coming). He is very very afraid now. He will do what he can to escape this faith, so what will he do ???? I think he will be Cersei’s doom, she is beyond repair now , she obviously wont repent so no Kingdom of heaven for her. He will kill her soon and that is the master plot. Cersei’s death will unite the forces of living. And yes, i think that Mountain wont escape his doom, but maybe he could repent still, there would be a moral to that, don’t you think ??? Sorry for breaking this riddle for you , but hey, you googled for it ..