Ok... You know why they reworked the original story? Because if the first game the "traveler was evil" Then what would we do for the next few games? It's called character development. The traveler will show it's true face, and it will add longevity to the game. Think of this like a book. If you read the whole book in one week, you finished it. You read a chapter a week and you have a much longer time till completion. On the flip side you talk about the Light and darkness as if they were good and evil. What if the Vex, Cabal, or Fallen are truly the good ones? For the Cabal and Fallen especially there really isn't much grimoire stating them as evil beings.