Global Cataclysm: I Turned In a Portal

[Apocalyptic Sci-Fi] [Portal] [Otherworld] [Mecha] Disaster strikes, and the surface is blanketed by extreme cold and radiation. To survive, humanity builds underground bases. To save his younger sister, Mu Chengzhou hands over a portal. From then on, with the nation's help, he dominates the other world. For his safety, the nation develops a suit of armor modeled after Iron Man: the Qianyuan One! For his health, the nation revises the Taoist scriptures, setting him on the path to immortality! For his sister, he gathers every spirit herb in the other world. To ensure the nation's survival, he turns the entire other world into the country's manufacturing plant.