The novel " Overlord " did not explicitly state that Momo was the only player in existence. As for whether Momo had conquered the world, there was no clear answer. In the later stages of the novel, Momo worked with other players to fight against some powerful enemies and finally conquered a part of the world. However, there were also many other characters in the novel, including other players and NPCs, who played an important role in Momo's world conquest. Therefore, whether Momo conquered the world or not depended on how the concept of " conquering the world " was defined. There were many powerful enemies in the novel, including other players, NPCs, and other forms of evil forces. Momo needed to fight these enemies and win in order to maintain her world conquest.