A week or so ago (as of the time of this writing - Sat Dec 1 22:28:47 MST 2001) my brother said to me: "I think it would be kind of tough to have a TL 0 Campaign." I took that as a challenge. What follows is, in my most humble opinion, a rather intriguing TL 0 gameworld.
A group of cavemen were living a normal caveman life until one day when a huge flying saucer descended from space. Of course, our lovable cavemen didn't know it was a flying saucer, nor who these strange little green men with the big bulging eyes are, but all they knew is that they were scary and powerful and they must be their gods, come down to visit.
The Aliens, for their part, are very inquisitive types, delighted to experiment upon anything they happen upon and unconstrained by any tedious "Prime Directive", so they are delighted to have found some beings to toy with.
After a good deal of toying, the Aliens arrived at a goal: they waned to help accelerate the development of mankind. To that end, they have devised a plan whereby they will issue challenges to the clan of cave dwellers and push them to make new discoveries that will help them to achieve Tech Level 1.
The Aliens will appear to the cavemen on a regular basis in a very "Wizard of Oz" fashion, commanding them as their gods and rulers to go out and accomplish some task that will help advance their development toward TL 1. This is the hook that can be used to get a lot of adventures started.
But what, exactly, should the tasks be?
The following is an (incomplete) list of things that the Aliens could challenge mankind to achieve.
Frequently, gameworld settings are billed as being an "Age of Discovery": Steampunk / TL 5 gameworlds are replete with new discoveries ushering in the modern age; Modern / TL 7 gameworlds can feature any gadget read about in the Sharper Image catologue; Starfaring / TL 9 gameworlds can feature any number of new technological advancements as contact with Alien life is made.
So, if all those other tech levels can be "An Age of Discovery", why not TL 0? It stands to reason that it would; after all, you've got no place to go but up.
Referring to the earlier list of tasks given by the Aliens, the discovery of one thing could be the hook for the next adventure. For example, they might develop a writing system in one adventure and then the hook for the next adventure is receiving a letter. Likewise, they might develop seafaring at the climax of one adventure and the next one begins with them taking a voyage by ship.
The following is a breakdown of some of the major features of this gameworld.
The time will probably be ~3000 BC or equivalent.
A good location would be someplace with a variety of geographic features nearby. A coastine, a river, some cavernous mountains, a forest, ice to the North, a desert to the South, a jungle farther inland. Plenty of settings for things to take place. Keep in mind, that the landmass we are dealing with is Pangea (pre continental division), so you can pretty much design your own planet.
Most player races will be human, but they needn't be the only sentient race at this time. Many of the traditional Fantasy races could be around; Dwarves and Giants are easily made with the Dwarfism and Gigantism disads. With Gamemaster approval, a player could even play an Alien, disguising himself as a human so as to walk among them and study their progress. There may very well be sentient dinousaurs as well.
Animal life in this gameworld is potentially more diverse than any other. In addition to typical livestock / game animals, any dinosaur could emerge. (No one said this was going to be a historically accurate gameworld.)
All kinds of animals could emerge that are now extinct but we just haven't been able to find any fossils of them in the modern day. Likewise, there could be any number of mid-evolution creatures that crawl out of the sea and terrorize the caveman, leading to the age-old "monster on the loose" adventure seed.
Additionally, the Alien rulers could have brought all kinds of animal life with them. After all, they flew here in a big ship. (Maybe it's their version of Noah's Ark?)
Most any other tech level is spiced up by the addition of magic, TL 0 needn't be an exception. This gameworld will be high-mana and Magical Aptitude is a commonplace advantage requiring no Unusual Background. The explanation here is that the Earth is young and unsullied by science and technology, and Primal Forces still run wild.
Magic at this tech level will take a very shamanistic form, with animal and sun totems commonplace. It is also likely that primitive "witches" would appear, replete with stone cauldrons.
Limitations will need to be placed on any magic that requires writing. At least, until they develop a writing system... :-)
The presence of the Alien rulers is adequate explanation for the presence of Psionics. The Aliens have very advanced Psi powers and can recognize those powers in the cavemen. Given the Aliens penchant for experimentation, they could abduct some select humans and train them on how to use their Psi powers.
As with magic, no Unusual Background is required.
H.P. Lovecraft, in his Cthulhu Mythos, described the dark denizens of the night as the original inhabitants of the Earth, who, through misfortune or misdeed, lost their birthright and the Earth was given to humans. That's just too good to pass up, so we're definitely going to make that premise part of our gamworld.
As with the previous, any of the following characters could be made with no Unusual Background to explain it; it's just not that unusual.
Vampirism is prevalent and any player is allowed to make a Vampirie character with any appropriate ads / disads.
Lycanthropy is likewise prevalent and any were-creature can be made. The prevalence of such beings is accounted for by primitive animal worship religions. Keep in mind that lycanthropy at this tech level could be far more interesting than at any other. In addition to all the classic were-creatures (wolves, snakes, monkeys, etc.) you could easily have Were-Saber-Toothed-Tigers, Were-Wolly-Mammoths, Were-Ankylosauruses, Were-Pterydon, Were-Icthyosaur, and, of course, the soon-to-be-far-too-popular Were-Velociraptors. Seriously, the sky's the limit here.
Zombies and Mummies? You betcha. Primitive burial rituals were very interesting and rather involved. Some cultures would bury a man with the carcas of his favorite game animal. Imagine what might happen if some "unfinished business" brought the pair of them back from beyond the grave...
Ghosts could also be prevelant. And before you start asking: "Hey, just how many dead people would there be at TL 0?" Keep in mind, we don't know exactly how long this Earth (or at any rate, the one in this gameworld) has been around and what inhabitants lived here before man arrived.
And Beyond... There's really nothing stopping you from coming up with whatever denizens you desire. Dig up that old D&D Monstrous Compendium if you run short on ideas.
Likewise, it is likely that some form of the Occultism skill exists to help the otherwise unassuming caveman spot who these dark denizens are, where they came from, and how to get rid of them. (Thusly bringing us to a TL 0 Vampire Slayer character...)
I know what you're thinking: "Cyberware and bioware in a TL 0 campaign? Are you kidding?"
Well, remember that this particular gameworld has those aliens that like to experiment on humans... They probably would treat them like guenia pigs to test out their new cyberware prototypes. Therefore, as with the previous, no Unusual Background is required if a character wants to have cyberware or bioware, but it would probably be appropriate to have some complementary disadvantage, like amnesia or a phobia.
Again, I ask: Why Not?
I mean, shoot, if we're going to have everything else, why not throw in the kitchen sink too? There actually is a precedent here (albeit a rather silly one) in the form of Captain Caveman.
I'd feel a bit hypocritical if I were to require an Unusual Background for any super powers afer uncorking the lid on everything else. Heck, why not; we'll just say that the aliens hit them with a frill-o-zap ray or some other dumb orgin story to explain how they got him. ("Zog hit me on head with rock and when I wake up, I shoot lazers from eyes!")
(With apologies to TSR -- maybe)
The historical nation we will pattern this gameworld after is Ancient Egypt. In addition to the varied geographical features, the culture and mythology were extremely interesting. Egypt was also the birthplace of both Western and Eastern religious / intellectual traditions, making nearly any cultural reference feasible.
Players could expect to see appearances by animal gods, a la Anubis, or even anthropomorphic Judeao-Christian / Oriental gods. Said gods could be real deities or could be the Aliens in disguise.
Alternatively, you could go for a more "Arabian Nights" feel, replete with Djinn and Elder Gods.
Something that spices up any gameworld is the prospect of getting off of it. There are plenty of ways our prehistoric protagonists could leave.
The following references could provide further inspiration.