User blog comment:Godisme/Gray vs. Doriate/@comment-3424593-20130906210035/@comment-7418318-20130906214946

Whoever said that Gray knew it would work. "If I could somehow controll this villages ice" doesn't sound like he knew it would work for me, but rather that it was a desperate attempt or at best an reasoned out theory. Either way he came up with it on the spot and luckily for him he was right.

Azuma didn't use it? He outright tells Erza that he's taken over the magic of the island and is now using it to suck everyone's magic out of their bodies but left Erza out of it for their duel!

Edolas: Yes and how did the energy get into the lacrima? By sucking it out of other magic sources. Only that they are transforming it into whatever they need, rather than shooting it out untransformed like Gray did.

Why have they not done it? I already answered that in my previous comment. Whenever there was need, there was no suited power source available. And when there was a powersource available, there was no need to use it.

Name me one instance where they had both the need and opportunity to suck magic from some other phenomenon that was not under the controll of an enemy at the time and use it to power one of their own spells.

Apart from that Gray didn't know it would work. You only try out things of which you don't know if they will work in a desperate situation in which every other possibly useful option has already been exhausted.