Dark Knight Representative

[Eloah]

We don’t even know if Arbert is alive. And while not every player character has been a Dark Knight, they have all been the “Warrior of Light” throughout the story.

True we don't know if Arbert is alive, that's what makes him a possibility. And Dark Knight, Warrior of Darkness, and Warrior of Light are all seperate things. Contextually, within the story, we can't be a Dark Knight and the Warrior of Light/Darkness, so an NPC has to be the Dark Knight. Gameplaywise, we can be anything.