If you go to the floor 28 and Melkor kicked you out. Erza will tell you to rest, then skip one day. Go to her and give Erza one XL Wisdom Potion, and she will tell you to look 3 pieces: The first one is from Solan (buy it for 2000 gold), the second is from Ginny (this one is sealed), and the third one is from Luna (she asks you to find it. It's behind the couch). Then go back to her and her quest will be finish, now you can see a new scene and the new ability.