That's exactly what it is, I just watched it again and no way could it be fire, fire doesn't melt ice that fast. Like you said, it's breaking the spell of magic, it just instantly rips that wall right down. Here's another great shot from that episode, from a distance. Other people didn't believe me when I said it's from the show, but it is. That's one of the things I love about GOT, they put so much into it that even the most hardcore fan never gets it all in one viewing. You have to watch each episode multiple times to get it all.....
