Darkness [Spoiler Warning]

[Gilraen]

We, as the heroes of the game, will never be swayed from our righteous path. This is the nature of the Japanese RPG hero, and as such everyone playing the game. It's the rare series where the Hero can break free of 'destiny'. Mostly Atlus' RPGs. This said, I can't help but think that the Warrior of Darkness is...

Derplander, or at least Mirror Derplander. He appears in cutscenes as us so it stands to reason that, in the Ascian's world there's people just like us, saving the world in the name of Zodiark while the Ascians fulfill the roles of the Scions.

But that's just a theory...

...based on the Wings of the Goddess storyline in XI.

Append: Clarifying myself.