In the year 2013 World War III erupted in a nuclear storm. Billions of lives were erased from the world.
When air raid sirens sounded over Moscow, citizens had less than five minutes to find shelter. The most fortunate among them - or perhaps least - were able to take refuge inside the city Metro.
There they survived by making the most of their surroundings. Salvaged parts kept vital systems running. Citizens learned breed livestock, and cultivate produce, left on the supply lines.
In the meantime heavy radiation drastically twisted the world above. Familiar creatures vanished, and monsters clawed their way to the surface. With time, and human error, the Metro began to decay; while the surface above remained irradiated and uninhabitable- the very air toxic for decades following
Even annihilation was not enough to pacify humanity. Within only years, the Metro dissolved into war; primarily conducted between factions that would become known as the Red Line and Fourth Reich. Where these radical factions are not attempting to disperse - or forcibly impose - their radical ideologies, the vast tunnels of the Moscow Metro are rife with mutants and murderous bandits... Among other Things.
27 years later the last remnants of human kind fight for survival beneath the desolate bones of Moscow.