Torn Quest Lore Drop: Fools and Undead in Rever (Forms of immortality)
Or also: the two (main and most common) ways of becoming immortal in Rever.
Somewhat.
Thing is, it is more accurate to frame one as "not being able to die" (Fools) and the other as "being banned from entering the afterlife" (Undead).
And that is because both becoming a Fool and becoming Undead are rooted in soul magic. And as mentioned: an undead soul is one that has been banned from the dead souls in the afterlife for especially heinous deeds and crimes they've done in the living world (for example, they were a nazi or a fascist or were willing to do the same kind of fucked up shit as nazis and fascists do), since that reflects a willingness to continue just that in the afterlife as well. In short it is not in control of the undead one, their bodies start to decompose the moment they do die on a technical level, but their souls stay inside, having to feel themselves rot away at every moment every second for eternity. All while they still can move around in their ever more breaking bodies that fall apart bit by bit, more and more, until the sun explodes and then some more. Of course many undead try to undo this or slow it down by the usage of dark magic (mind you, here it is the biology magic and as a result the only one capable of doing any healing), but sooner or later they too do become unable to continue with that.
A Fool's soul however is... well a soul to which something happened that split it apart. Either through a very intentional (and risky) usage of soul magic (you might easily end up in the afterlife in shambles instead), or indirectly as a byproduct of intense hate and loathing. Either from an external source (others hate and loathe you enough) or an internal one (you yourself feel self hate and self loathing strong enough). The splintered soul as a result is unable to pass on into the afterlife, unless it manages to piece itself together and heal again.
You're getting a fool for this type of immortality because no one would intentionally seek it out. While yes, it's true that you won't age beyond a certain point with that one (because something something, DNA and chromosome ends cannot be shortened during cell division or something), you can also still feel pain and get hurt and put under torture, loose limbs, gain scars, get paralyzed, etc. all that fun terrible stuff that still limits you within your own body. And if you became a fool by being hated by others enough, you're almost guaranteed to be under constant risk of any of that stuff. In short: you're not going to have a fun time here either.
In the first book, Ona Tiena is that type of fool. And so is also Anosrep.
Neither seeked it out intentionally. Ona in fact actively seeks death, but has so far been unable to ever find it. Anosrep in the meantime had seen and witnessed some fucked up shit from before the downfall of the Sapiens that he feels responsible for. So much that he took on an oath (that he cannot break) that he would make sure that all of that would be either stopped or undone before he would allow himself to heal enough to be able to die again.
There is a third form of immortality, technically, but that one has the side effect that you won't be able to sleep. I won't elaborate on that one further until I'm like at book 8 or so.
