The exo stranger tells you that the traveler/speaker (or was it light?) is not what they seem to be suggesting we might of been used to fight off the darkness for the traveler as it knew it was being followed. you find the shard of the traveler in one mission against the hive because they are doing some ritual for it to not be able to heal hence the broken bottom part of it through the game. also the servitors the fallen worship as gods seem slightly similar to the traveler, machine balls that heal and provide so much. maybe the fallen are called fallen because they were used by the traveler to try and fight off the darkness but they failed and got f****d up and now they seek revenge or something.