The Only Supplier of Doomsday

Natural disasters are sweeping across the world, zombies are rampant, superpowers are awakened, and order is broken down. While everyone is struggling to survive, I am sitting in an absolutely safe fortress, controlling the only trading rules in the end of the world. Everything is sold here: from bread and water to mecha battleships; from power awakening potions to steel cities. "Want supplies? Give me crystal cores in exchange." "Seeking asylum? Check out the price list first." "Challenge the rules?" Sorry, our store does not provide this service. Violators will be responsible for the consequences. I am Yu Zhou, the only supplier of doomsday and the last absolute rule in this collapsing world.