The year is 2033, five years after a worldwide biological war. The surface is a barren waste, the air toxic to a human's body after only minutes of exposure without a gas mask. Humanity is scattered, on the brink of extinction, but pockets of life have survived by fleeing down into the underground. Forgotten metro lines have spawned settlements, and humanity endures its self-inflicted trials. Creatures have mutated and evolved to take the place of the formerly dominant race of the planet, and they regularly clash with humanity for resources and space.

Paper money is worthless in this time period, used only for kindling of fires if it is kept at all. Ammunition, and sometimes guns, are the new currencies of the time. Food is also valueable, worth more than its weight in ammunition in some places, because it is so scarce. Many of the average citizens rely on the Rangers, the brave souls who forage into the tunnels or even the surface, to survive.

The largest settlement in three hundred miles is the Brendis Settlement. It resides inside of a natural cave formation, discovered by a group of Rangers on a foraging journey. It has thrived, mainly due to its extremely defensible position. There are only two entrances to the caverns, both enlarged to allow a hand-powered cart to travel along scavenged rails. These give the Rangers a faster mode of trasportation, and a way to bring back any large supply caches they may find abandoned in the tunnels. Both entrances are heavily guarded, each with armed men and a mounted flamethrower to deter the creatures of the tunnels.

Humanity's main enemy in the underground tunnels are the Nosalis. Nosalis are most comparable to pre-war burrowing rodents. They stand roughly three feet tall, stumbling about in a rudamentary fashion on their hind legs to watch for prey. When they catch the scent, they revert to a four-legged sprint that they can maintain for respectable distances. They are pack hunters, usually in groups of five to eight, and will immediately attack a lone target. Groups of even three people are often enough to deter them. The danger lies in their sharp claws and teeth, which they will often use to maim a target. They then begin devouring the target, often without finishing the kill first. Nosalis are extremely aggressive.

On the surface, a flying beast known as a Demon rules the skies. Demons are large, powerful predators and have a human sized body with a knobbly spine and a short, bat-like tail. The Demon has four prehensile limbs and two large wings. They have a long head with a blunt snout, consisting of a bat-like nose, green eyes with vertical cat-like slit pupils set far apart on the head, and a large mouth with 4 primary teeth and several secondary teeth. They often hunt in pairs, and are easily deterred by entering a building. They avoid restricting their ability to fly, but have been known to reach inside buildings and attempt to pull rangers out. They are very difficult to kill, because they retreat if their initial ambush fails, and are strong enough to tear a man in half.

Industry was crippled, and is only just now beginning to reform in the larger settlements, such as Brendis. This highly restricts the weaponry humanity has available to protect itself. Explosives are almost never used for combat, due to the risk of caving in a tunnel. Post-war ammunition is known as 'dirty rounds', and tend to be harsher on guns when used. The one model of gun mass-produced in Brendis is affectionately known as the 'Bastard'. The name comes from a combination of its tendency to spray inaccurately on automatic settings, its tendency for overheating, and finicky reloading system that jams often. These shortcomings combine to give the weapon its name: It's a real bastard to use. Pre-war ammunition is known as 'clean rounds', and is one of the most sought after items in the metro. It is both a cleaner shot as well as a more powerful one. Pre-war guns are also valueable, and are often the prized posession of any Ranger fortunate enough to own one.

That's it for the basics. Welcome to the metro. Do you have what it takes to survive?