assuming the barons were under isolation within the PoE, and couldnt smith weapons out of dead vex and hive gunk during lunch hour, then it stands to reason that he had his hands on it before he was captured. it's unlikely it came from the mindbender, as "the throne world came after cayde" (-aunor) and he wouldnt have had the ability to create it before the events within the prison. one very clear suspect is the drifter. we know he's encountered the barons on occasion, due to his voice line before the boss fight in the PoE strike-"looks like the trickster left you a present. always hated her. ah, but she made me laugh." surely the drifter, a man who commands interdimensional spectres and demons, would kill someone he hated. but we are the ones to put the final bullet, blade, or other concentrated violent space magic into the trickster. this leads me to believe the drifter has had dealings with the barons in the past, and due to his power over the darkness, and his very clear knowledge of what Thorn's ballistics are like (due to the helmet found in the last word quest) it would stand to reason he could outfit his benefactors with similar ammunition. it may be that he didnt intend for it to be used on cayde, but this still puts some responsibility on his shoulders. secondly, savathun may have been responsible for it falling into the barons' possession. think about it. without cayde's death, we would never have made it to the dreaming city. without access to the awoken stronghold, we would never have slain riven. and without her death, savathun's curse would never have been unleashed. i think its plausible that cayde's death, our involvement in the dreaming city, and anything to come or change with the curse, will all be according to her plan. its unsettling that we may be the pawns of one of our greatest threats, but that's a different topic. uldren is a liklehood, however i doubt he would be directly responsible, as before his "possession" he was somewhat in favour of the guardians. if he had the arms to kill the light in d1, he would have mentioned it, at least. i'd like to hear other ideas on its origin. but one thing's for sure. there's something or someone out there responsible for cayde's death. the hunt isnt over.