☢ S E T T I N G ☢
Zombies. They are everywhere. You're outnumbered about a million to one, and guess what? You look pretty tasty.
Chances are, you didn't ask for this. Maybe you come from a world with no violence, no wars, nothing to worry about except that party you were planning for next weekend. Or maybe you've already saved the world, done your part, and now you want a break.
Too bad.
You're stuck here now. There's no telling what force brought you here, but you woke up in a tiny room with a red barred door, without any explanations besides a faded military poster on the wall and a few, frightened words scribbled across the decaying white paint.
You can call for help and wait for someone to come get you-- or try to make it alone. You'll find a GPS/Phone device in the Saferoom with you, as well as guns and plenty of ammo. The GPS will show you the way to safety, or you can use it to contact outside help. If you decide not to wait, you can try to follow the GPS on your own and make your way to safety-- You just have to get through the hordes of zombies, first.
But there is hope. Safety. Security. Friends, if you like that sort of thing.
There is a military base-- a fortress-- just outside the walls of the city. It bristles with impenetrable walls and devastating defense weaponry. Inside is something of a miniature city, with apartments, kitchens, training grounds, and all the army-issued amenities anyone could ever ask for. There are others like yourself housed here, people who were brought here from other worlds-- but they do not run this fortress. No, the brute strength of this place is manned by what remains of the military on this forgotten world.
After a quick medical check to make sure you aren't infected, they'll welcome you. Well, 'welcome' you as much as people in full-body hazard suits and gas masks can feel 'welcome' to anybody. The soldiers and doctors won't take off their masks around you, but they will offer you food, shelter, and safety. Sanity. Everything a growing body needs to survive. All the military asks of you in return is one thing: that you occasionally help them 'control' the zombie population.
In other words?
Kill zombies. A lot of zombies.
Thing is? You're immune to the infection. Completely immune. The military definitely is not. You can be clawed, bitten, spit on, jumped on, horded, tackled, pulled, and scraped by zombies and still come out clean of infection and without risk of turning into a zombie yourself.
The military can't. (Of course, you can still die, so you might want to watch out for that.)
So the military will ask, politely, that you help them out occasionally. Think of it as payment for room and board. The military is trying to take back parts of the city and the country-side, one sector at a time. They can succeed, with your aide.
Occasionally, the Fortress will give out a shiny, brand new, army-sanctioned map with detailed instructions and aerial pictures, depicting a new sector they wish to reclaim. They'll send you out, fully armored and weaponed, to travel the length of the map and clear out the beginning zombies. They'll pick you up once you reach the end.
If you don't have weapons, they'll provide them for you. If you don't know how to use them, they'll provide training. And you'll always go out hunting in groups with other survivors, so you never have to worry about backup. The military will even come and save you with rescue vehicles once you reach the end of a map-- so no worries!
Well, maybe you should have a few worries.
But it's a tough world out there. Brutal, even. So far as you know, the Fortress is the last human dwelling still standing-- so it's best to play nice, for now.