Ok, so here is what I think about the Vex's lore. But first you have to know this, the Vex Mythlocast grimore card states that the weapon is from some far-flung corner of space and time and is [i]mysteriously[/i] fit for human hands. I think that Atheon is locked up in the vault. Not posted there. It is a vault, after all. But anyways, we know he doesn't like the vex because of his name. That is why I think templar is in the vault. He is there to guard Atheon and make sure he doesn't get out. So how does this all relate to the Vex Mythlocast? You'll find out. So what I think happened was that Atheon heard word of Kabr. Or [i]sensed[/i] him. It seems likely. Then, Atheon makes a plan to break free of the prison. He makes the Vex Mythlocast for Kabr and his fireteam. However, Kabr dies and Atheon has to keep the weapon. This is why it drops from him during the raid. We don't know Atheon is a friend though and we kill him. That is why he fights back, and he fires first because he thinks guardians aren't powerful enough to reach him. Thus making him think that the vex sent us, and that is why he shoots first. So tell me what you guys think about my little theory. I'm open to holes in my story and tell me if you find some. Thank you for reading.