User blog comment:IamJakuhoRaikoben/Chapter 350: Gray vs. Doriate, Review./@comment-7418318-20130906165041

I don't think Gray's attack was powered by Nakama Power this time.

He just used his head again. If he himself doesn't have the necessary magic power, take the power of an alternate source and mold that.

That actually makes a lot more sense then the sudden "I have to save my friends and thus I'm getting stronger out of nowhere" stuff Erza repeatedly pulled off.

Also the power came from something that could freeze over the entire village and it's giant population, so naturally it's very powerful.