Well this theory goes out to my friend alex. Hes been thinking that Xion has the power to use other peoples power.as you all know she has been seen wielding a keyblade maybey she got this power from a keyblade wielder (roxas?, riku?, sora?). Maybey the fire she used when fighting along side roxas taken from axel. If u guys agree, disagree i would love to hear ur comments.