Save the World Starting from the Dungeon

Lear never thought that one day such a thing as saving the world would fall on him. In his previous life, he was just a warrior who relied on his talent to become a legend, but when he went back to the past and looked at the land that had not been ravaged by evil gods, he knew that he had to do something. This is an era where magic and steam coexist. The mythical era of belief in gods has long come to an end. Except for those supreme beings, only gods who are willing to give up everything can survive in this world. Steel, gunpowder, magic potions, evil gods, spells, and faith. Lear returns to the underground city twenty years ago, where should he go?