I kind of saw the whole 'Become the Warrior of Darkness' coming for quite awhile. Though, I don't think it was really that hard to guess given what we've been told previously during past events. Personally, I image the likely scenario is that solution is likely do with mastering both of the powers or Light and Darkness in order to find a solution. Of course the course question is "What does it mean to be a Warrior of Darkness?" Primarily the status of Warrior of Light seems to come down to the fact that we wield the six crystals of light which represents each of the primary elements in the games lore. Is it a situation like in Final Fantasy 4 where there are equivalent crystals of Darkness or is it something else entirely? Is it a situation that requires a change of mindset or approach? Do we abandon the Crystals of Light that we already have or does something else happen to them? There are definitely far more questions then their are answers.