Leveling System is a gift that some people get. Having it meant being able to have the power that was the result of hunting monsters in the Dungeon, becoming a Hunter. Oliver didn't have the System, making him just live as a human. This wasn't a problem for most people, but when a human had problems with the Hunters, life would become difficult. However, when he despaired of the Leveling System that he couldn't get, he obtained a ring with a space inside, containing ancient books that turned out to be cultivation methods and skills. He couldn't hunt monsters to level up, but he could increase his strength by meditating. The Hunters, they were no match for him.