Possibly the earliest you can get this, is about half way through the game, if not more. You will eventually come to an underground library that has a big sphere in the middle. On the ground floor of the library, there is a circular bookcase towards the top of the screen. Press on the left side of that bookcase, and you'll find a book called "Pyro Pages".
Go through your inventory, click on the book and read it. It will teach Edessot a new move called Supernova. This move requires 5 gather, and as soon as you use it you will earn this achievement.