Lin En transmigrated into a fantasy world as a useless apprentice mage and activated a "Thirty-Year Comeback System."
Other people's Systems give them god-tier talents from the start. His only assigned trash missions, and all his rewards are junk.
So he simply gave up on the System and studied magic through structural mechanics, eventually becoming a mage recognized across the continent as a prodigy.
Everyone thought he was a born genius. Only Lin En knew that he was just an engineer who could draw blueprints.
Then the apocalypse arrived, and the abyss began devouring the earth.
At that moment, the useless System he had cursed for thirty years finally spoke for the first time.
A well-developed and logically rigorous book.