I'm Back from Doomsday Purgatory

The end of the world is not a natural disaster, but a carefully planned conspiracy. When the last city was reduced to ruins by the pollution of "Purple Eclipse", the legendary mecha pilot Lin Fan, piloting the mecha "Long Yuan" that combines ancient martial arts and modern biotechnology, carried out a desperate mission - traveling in reverse through time and space, returning to the first day of the disaster, trying to reverse the fate of human extinction. However, the "past" he successfully reached was not what it was in the records. The destructive purple beam of light did not erupt from the ground, but was accurately shot from the collision center of "Prometheus", the pinnacle symbol of human technology. Deadly radiation, deformed monsters, distorted space... Behind all of this, there is a mysterious organization called "Gatekeeper". What makes Lin Fan even more weird is that the biological mecha "Long Yuan" he pilots absorbs emotional energy because of his obsession with saving lives and carrying the dead, and constantly awakens powers beyond understanding: ancient martial arts runes, evolved and mutated nerve cords, intuition to understand crises... Each evolution is extremely powerful, but step by step it also touches the terrible truth that even super technological civilizations regard as taboo. Standing alone at the beginning of the apocalypse, Lin Fan soon discovered that preventing this crisis meant becoming an enemy of a huge shadow that had already penetrated the world; and with every life saved and every second of history changed, the mecha he relied on and himself were sliding towards the inhuman abyss. The ripples of the space-time paradox are spreading, and the will of the abyss behind the "door" is whispering and echoing. He is the only variable and the last echo of human civilization.