The Halo Setting is a science fiction universe primarily featured in the Halo video game series. It is set in the 26th century, where humanity has expanded across the galaxy and encountered various alien species. Central to the story are the conflicts between humans and the Covenant, a theocratic alliance of alien races. Key elements of the Halo Setting include the massive ringworlds known as Halos, which were created by the ancient race called the Forerunners. These structures are designed to contain and combat a parasitic species known as the Flood. The narrative explores themes of war, survival, and the struggle for power among different factions.