Didact (halo) 1.0

Forerunner Promethean who held an extremely high status in the Forerunner society as supreme commander of the entire Forerunner military. He wholeheartedly believed in the Mantle of responsibility the Forerunners held to protect life, and initially opposed the Halo array as a sin beyond measure. He was also the lover and husband of the librarian. He serves as the primary antagonist in Halo 4
source: http://halo.wikia.com/wiki/Shadow-of-Sundered-Star