First, I want to congratulate you on delving into the Deep like you did. Second, I see the story as a battle between Light (the Sky) and Dark (the Deep). The two opposing forces are trying to shape the universe into a final shape. The Sky attempts Order through Golden Age utopia. The Deep attempts Chaos via dystopian genocide. Their agents? The Sky has the Traveler, the Deep has the Worms (whom employ the Hive). We know that the Traveler visited many worlds bringing Golden Ages, but it is only on Earth that it raised Guardians. The power of the Deep feeds off of Light, and even transforms it (all lower Hive tribute the Light they consume to higher ascendants until it finally reaches Oryx and his sisters to tithe to the worms). So here is the kicker: Guardians are the Light equivalent of Taken. Just my theory.