I wanted to see what would happen if I unretired Pis the charcoal brute who doesn't have a body
He gets reincarnated instantly into the body of a mountain gnome named Yifles and dreams of bringing lasting peace to the world
This could be a glitch of his character ID looking for a body, but I'm guessing one of the previous players decided to mess around with him lol
It's definitely a glitch. Half the creatures returned in the Anti-Rapture that I tried to unretire throw me in a different body, sometimes directly into a literal unnamed hell demon. I'm 99% sure Yifles doesn't have the same ID as Pis. In my experience, it works with half of them (of course, my testing rate was of about maximum 10 of about 100,000 returned, so that statistics might not be representative of the actual odds), but we probably need more testing. I also suspect the time to posses bodiless Returned was directly after the Anti-Rapture and that things will go more wonky the more we retire forts and adventurers.
So I tried playing around with things, trying to bring back a human that was killed, then Returned in the anti-rapture, but then died of old age. I went into gm_edit and set his death year to -1, and then used full-heal -r to bring him back to life. The corpse disappeared with no sign of the guy I revived, but he was listed as 'alive' in Legends mode again. So I used unretire-anyone to try and possess him, but it sent me into some random farmer instead, unfortunately.
However, I learned that if you fast travel while "borrowing" a body in this way, the person doesn't actually travel. Instead, you possess some other random entity (any animal, person, or demon). You can't seem to be able to retire like this, but if you succumb to starvation or die in any way, the original Returned that you tried to revive doesn't "die" and they can be continually used to unretire and possess random creatures around the world. The main drawback is that if you're stuck underground or in hell (or teleport to Deephalls for some reason) then you'll have to pass two weeks to possess someone else.
Unless someone knows of a way to edit a specific hist_fig's body and teleport them without them being physically present, I don't think certain Returned can be made interactable again. But maybe this can be used for some weird astral-projection / wandering spirit playthrough? It'd certainly be a challenge to make it to Boltspumpkin like this. Dikbut, how did you even manage this mass-resurrection anyway??
Edit: Also worthy of note are that several adventurers, after having been dormant for centuries, are now in a state of Quantum Flux (as coined by Lurker). They are alive, but don't exist anywhere in the world until someone sees them by random happenstance, they are affected by a world-gen war, or they are unretired. This can be easily seen by going to the unretire screen of Ketas or Nom or anyone whose map screen doesn't appear immediately. Go in and out of their confirmation screens, and you'll see that the unretire location changes every time. So if someone wants to find them for whatever reason, they might have to unretire them first.