He also spends some time trying to play around with the other powers - there's six distinct sets, not including the teleport, that stand out in his mind, and he had to give one to the controlled body (and it can't use the other five, and his main body loses access to that one). He chose to split off the one he thinks is the cybernetics power, and indeed with some fiddling the controlled body manages to start summoning random cybernetic implants. Mostly weapons-themed, ending with some accidental rockets shot off (not towards main body), but gradually as he gets control of it trending towards more broadly useful things.

"Might be able to use this to give that body a chip for a chip-locked computer," he says.

"Oh, that'd be useful! Who... invented all this shit. This is clearly designed and I don't think you happened to have a lot of rocket specs in your head."

"I have no idea! Maybe the aliens, if the Rinnegan came from them? How does the eye know which to access and what's available and how to implant things, though..."

"Yeah, that's really strange. The aliens were roughly humanoid but there should still be all kinds of weird wrinkles in how to hook things up for usability."

"It's slightly weird having an eye with - a user interface."

"It sounds it! The user interface doesn't have 'click here to learn about the manufacturers of the cybernetic tech tree'?"

"Not that I've found."

"Inconsiderate."

He nods. "I think I'm getting low enough on chakra I should probably call this sort of testing done for today... The main powers I haven't tested - the soul-stealing, the giant animal summoning, and the restoring damaged possessed bodies - will probably be more expensive to test for the last two and extremely difficult to test ethically for the first. There's also the restoring the dead power, but the records were really unclear on if that kills the user or not..."

"...maybe it only kills whatever body you use to do it? I mean, don't try but there are two of you at the moment and that's a possible source of unclarity."

"Maybe. I think..."

He closes both sets of eyes, then opens them one at a time.

"I think only the main body has the relevant sense - I think the glow around people is souls, though I'd have to be near someone dying to confirm that. And I'm pretty sure if the main body dies, then so do the controlled ones."

"Still, if we had two or more people with the Rinnegan, and at least one didn't mind spending a good chunk of eternity as an undead, we could trade off and put each other back along with whoever else we can grab."

"Did the basement dweller have a glow before you took it over?"

"No. Still doesn't, actually, but that might be a 'I can't see myself.'"

"I can check? That being the only thing I can apparently do with a Rinnegan."

"If you feel like doing extreme eye surgery for that, sure? But I don't think it's essential, and I'm hoping there's some way we can get more people able to use the eye soon anyways."

"My version's way less extreme than yours, but yeah, it's hardly urgent."

"Yeah. Let's get heading back? I think we do need to figure out what to do about further Rinnegans, but we don't need to be standing here to discuss that."

"Sure." The shuttle opens up.

And board.

"I think given how easy I've found the interface it's possible 'using the Rinnegan fully' will be significantly easier in general for Uchiha. However..."

"However?"

"Only other Uchiha right now are Itachi and Obito. We could put some back as undead but them being able to use the Rinnegan would require them being fully alive, which runs into the problem with us not knowing what the putting-people-back technique actually does."

"Yup. Bit of a tangle."

"If there's ever been anyone else with the Rinnegan it might make sense to grab them..."

"Mustn't there have been, at some point?"

"The Sage of Six Paths, at a minimum, but I don't know if the resurrection technique works on half-humans. Still, we can try for him."