Did Gray some how used the same magic that got all the giant's frozen? what did he do?
An Ice that works on Demons... that rather than frizzing, it electrocutes them... gates of the hell... I guess that explains a bit. Looks like they have Ice Hell, like in Norse mythology, instead of fire one, that's why this special ice, that is unbreakable as well as super effective against Demons, worked.
Or what Grey did was simply release the humongous magical power, that by simply sending forward owned the beast...
So the observer can change size:
^oh I see, forgot about that thing, still no idea what it its.
P.S. my link is the one to Mangastream as well