[He actually hadn't considered the idea that souls could differ between worlds. The idea gives him pause.]

We don't even know how they harvest souls in the first place, so how the hell are we supposed to guess at that?

[Maybe he's just miffed he doesn't have an answer for that one.]

Yeah, but they wouldn't be experimenting without some kind of end game in mind. [Well, they could be, he guesses, but it seems like a waste of time to go through so much trouble just for the sake of curiosity.] They have to be using the data for something. They could be testing something.

[Unthinkingly, he reaches up to touch his fingers to his own collar as he considers.] What about...the stuff that's inside them? They drain and replace it...