Major recurring characters of the Halo multimedia franchise are organized below by their respective affiliations within the series' fictional universe. The original trilogy's central story revolved around conflict between humanity under the auspices of the United Nations Space Command or UNSC, and an alien alliance known as the Covenant. The artifacts left behind by an ancient race known as the Forerunner play a central role—particularly the ringworlds known as Halos, built to contain the threat of the parasitic Flood.
