Sometimes Zombies Happen

[Umbran]

I think that any world that has seagulls and rats is unlikely to suffer from zombies.

I think that any world that has undead "naturally" rising from the corpses of the dead is is apt to have cremation (or other form of bodily destruction) become a ubiquitous death rite. A world with magic that prevents rising of undead will have that become ubiquitous as well.

Undeath (well, the lower forms of undeath) is similar to mental illness, mutation/birth defects, terminal illnesses, or the plague. It's uncommon-to-rare, sad, it's bad, it might even be seen as an ill omen or Serious Bad News, but it's not necessarily "Foul Evil Afoot". Sometimes Zombies Happen. Some may see them as wounded or rabid animals; they need to be put down, both as a danger to others but also simply taken out of their misery.

So what kind of natural order would permit this? As in, what could be some causes, and what role could it serve as a setting element? What could go wrong with a world to make this sort of thing happen?

Well, to use your own analogy - nothing is "wrong with the world" to make mental or physical illness or defects happen. That's kind of the point - they aren't "unnatural" because they *don't* represent something wrong with the world.

 

[IstraRaugir]

I'd say that the way undead are formed is highly dependent on the specific cosmology and deities of the campaign world.
There are of course the common natural causes such as strong emotions, unfinished business, lacking burial rites and particularly gruesome deaths. The important thing is that you remain consistent with your rulings but to think the system through beforehand. (If a agonizing death causes Wraith, what is keeping a village from being massacred everytime someone is trapped in a burning shed?)
Secondly you need to consider how existing mechanics figure into the story and what effect that would have on how undead are viewed. (People will be hesitant to attack a necromancer's army if they believe their loved ones trapped inside can still feel pain)
And finally it is important to construct a way for (dangerous) undead to be dealt with that is consistent with your system and the effect thereof:

If zombies are raised due to lacking funeral rites is this a simple mechanic problem? (unburied zombies) Or is it because the person's spirit isn't appeased? ("Damn it. I might be dead but I'm not leaving without my lucky snorkel.")
Both systems can have profound effects on the game world: With the first the Dwarves are thrown into a crisis after a recent earthquake revealed that their honoured ancestors aren't exactly peacefull in their tombs. With the second the party may need the learn about their dead companion's culture because their burial rites are needed to bring him to rest.

P.S.: Just to be the devil's advocate (or the rat-bastard DM) I would rule that cremation is generally successful but leads to incorporeal undead in rarer cases (and you'll be wishing he just animated his fleshy hitable corpse instead).

 

[RedTonic]

Forsaken zones--anything that dies, is conceived, or is born there is "undead." The divine powers that be have forever closed their eyes to forsaken lands due to some great tragedy or blasphemy which occurred there. Or on the flip side of the coin, the forsaken lands are palpably claimed by some deity such that undead occur there as outlined.

Personally, I like zombie plagues; not only can you catch the plague by being wounded by an infected, but also by consuming anything corrupted by impure flesh: that means if you eat something grown on ground where rotted flesh wound up, or eat something that ate something that consumed a corrupted creature, or you drink tainted water, welcome to the Long Goodbye! Obviously this is more of a survival horror thing, so I don't think such a concept will ever catch on.

The original zombie is not a bad notion to bring up in this discussion, either--the person enslaved by a sinister rite (or a poison plus brainwashing, as it actually happens). They're not undead as we define it in game terms, usually--but that's where the modern notion arose. Original ghouls are also something to look at.

Personally, I classify incorporeal things as not undead, but other. I reserve undead for mobile, embodied creatures. I don't think of spirits as undead, even if they're malicious. I think it's just a pedantic thing, but it's my pedantic thing, and I wrote it, and I'm glad. so there. u.u

 

[Tinker Gnome]

Depending on the Planar setup of your world, you could say that undead are more likely to arise naturally when the Negative Energy Plane is "closer" to the Prime Material Plane.

 

[knightofround]

The Undead could be used for slave labor. Lucky criminals get executed for their crimes; the worst ones are doomed to an eternity of forced slave labor by abusive clerics. You could have an entire economy centered around Zombies doing all the labor-intensive jobs like farming fields, digging graves, mining ore, constructing buildings, etc.

Undeath could also be seen as a lifestyle choice. There could be a Zombie Pope out there, preaching that everyone has a right to unlife.