personally I think the forge of the gods DLC will be about how the traveler came to be on mars and how the vex god was created, linking it with Osiris, I think his interest in mercury lead him to find a greater vex power than the one located in the black garden that somehow changes him in some way to alter his path as a warlock. going from there I see the possibility of either finding Osiris and killing in a raid, or saving him in the raid as an ending to the dlc, strikes are in consecutive order finding clues that lead to Osiris and the story of his travels. hinting from the name I believe the endgame activity, whether it be like house of wolves arena, or a raid, I believe these activities will take place in an unknown "universe", now controlled by vex, so to speak where the traveler and the vex god came into existence, or were created. hence the forge of the gods. another version that could alter the story in some way is the traveler gives some sign of still being "alive" so to speak. If anyone has had ideas similar to this please add.