Light and Darkness always want to exterminate one the other. In theory neither can win even if it turns more towards the one or the other and this is what we call "balance". The emo party (WoDs) are already confirmed by Yoshi that they were both generic characters who represented us in the game and real characters in game. He simply came with the idea to actual use those models to create some more drama and surprise the fans. I think when they created that CGI long time ago they didn't have in their minds to use those characters as actual npcs in game and they came with the idea later on. I don't think there is an alternative universe or such. They are just warriors who joint the dark side at some point. Maybe after the Calamity. We will learn more about them soon either way.