World-saving Plan: The Only Savior

Worlds overlapped, and Alien Species descended.
Strange entities emerged one after another, as the shadow of evil spread wildly.
The calm of life was shattered, and Zhang Xiaoman, inside a fish’s stomach, accidentally consumed a system named “World-saving Plan”.
From then on, he became the only person among all humans with Extraordinary Power.
…
Inventing an ancient oath, he established a unique methodology, Cultivated Dark Energy, founded an organization, took Control of the Transcendent, and resisted invasions.
Well, this is actually the story of how a Big Con Man bluffed his way into saving the entire world.
PS: Contains elements of the behind-the-scenes, Cthulhu mythos.