The Darkness lurks to devour and control the universe, the real enemy we await demise for. It's evil rules 20,000 tortured worlds. It would seem to me that the Darkness is of physical formation, it is mentioned that it is the Traveler's most ancient enemy, and since the Traveler stopped ALL of the different species in our solar system from destroying humanity, it would also seem that the Darkness is telekinetic force that is controlling our enemies, attempting to cause chaos in order to destroy the humans. It would seem that the Darkness is what drove the different races to clash against one another and humanity. The Darkness is both the controller and evil being in Destiny. Well, I guess we'll have to find out!