In 2040, the "Grey Mist Virus" broke out across the world, and 70% of humans mutated into bloodthirsty zombies (divided into five levels: ordinary, speed, strength, superpower, and lord). The remaining humans established "survivor settlements" in the ruins. Resources were exhausted and order collapsed. The virus would spawn mutated creatures (such as scaly wolves and corrosive lizards), hiding the conspiracy of the "Umbrella Company" to artificially release the virus.
