A bizarre gray mist sweeps across the city, core transcription factors rewrite biological genes, mutant beasts burst from the earth, and doomsday descends in an instant. Chen Yan and four others form the Gray Erosion Squad, risking exposure to the mist to gain mutated enhancements, yet they must constantly fight the primal instincts within that devour their humanity. The M07 serum can only suppress it briefly, not eradicate the disaster. The squad ventures deep into perilous underground depths, sealing rifts and collecting coordinates of the source, exhausting every effort just to buy humanity a brief respite. But the wave of iterations does not stop, and hidden dangers erupt one after another across many regions. There is no cheat-like comeback, only a cruel game between humanity and mutation, a battle with no foreseeable complete victory.