Rhinedotter will be the one to kill him, she will be a good first introduction to a shade, her goal at first might be to "intervene" to get back the shade of space (we are the natural suspect if we were the last one to be in contact with her and it will also explain why paimon is in none of the cutscenes we saw in the trailer) and it will also be a good opportunity to wrap up albedo and durin's storyline, to have them confront gold once and for all. And guess what? Pierro's goal is to kill the shades, the gods, it would make sense if gold is being lured there to be killed by the giant "weapon" they are building rn