Where did the eternal title of dnf Muse come from?

Can't get it. Dnf refers to dungeons and warriors. According to official website, the game Dungeon and Warrior is a free role-playing 2D game developed by Korean online game company NEOPLE. In this game, the title of Muse cannot be collected permanently, but it can be bought at auction house. Dungeons and Warriors was released by Samsung Electronics and officially released in Korea in August 2005.