So at the ending the warrior of darkness was “introduced”. But why only now? Obviously, if there is a champion of light, there would be one of darkness. But why hasn’t he/she appeared till this late into the story?
Let’s put a two facts in order first:
1) Primals are manifestation of one’s imagination – In a sense, not quite what they said but you could interpret it like this.
2) The bishop looked at you (the warrior of light) as an evil entity
See the link I’m trying to establish here? The warrior of darkness that appeared in the cutscene was in fact the poster boy of Final Fantasy XIV – Who also appeared in both intro movies of FFXIV ARR and HW.
Using the poster boy as Warrior of Darkness may be Square-Enix’s way to prevent any form of spoiler leak. So here’s the big question: Are you, the warrior of light, in fact a primal yourself? If the warrior of darkness has finally manifested when someone imagined it, the same could apply to the warrior of light. After the calamity, the people of Eorzea may have hoped for a champion of justice that would aid them; they imagined you into existence.