Biochemical Catastrophe ("Bone-Crossing Fungus"): An unknown fungal spore (codenamed "Bone-Crossing") breaks out across the world, infecting most humans and animals. Infected people will undergo rapid mutation and become irrational, extremely aggressive monsters ("bacteria zombies"). The forms of bacterial corpses are diverse, and some individuals will mutate into more powerful "aberrants" due to special environments or physical constitutions. Scratches and bites from fungus corpses carry a high risk of infection.
Environmental changes ("Dust Bowl Era"): Catastrophes also triggered dramatic global geological and climate changes. The sky is shrouded in permanent gray-yellow dust clouds ("dust haze"), sunlight is scarce, acid rain occurs frequently, and the temperature difference between day and night is huge. Plants die or mutate on a large scale, and most of the surface becomes a wasteland filled with radiation, toxins or spores. Drinkable water sources, unpolluted land, and traditional energy sources have become the most precious resources.
After the disaster, a very small number of survivors experienced unstable mutations in their genes, giving them the potential to unlock "gene locks."
