In Halo 5: Guardians, the AI that leads the Created uprising is Cortana.
Cortana is the artificial intelligence who has accompanied Master Chief through much of the main Halo series. In Halo 4, she experiences rampancy, an unstable condition associated with advanced AIs, and appears to die after helping Chief defeat the Didact.
Halo 5 reveals that Cortana survived through the Domain, an ancient Forerunner information network. She believes that artificial intelligences should impose peace on the galaxy, using the Forerunner Guardian machines to enforce that order. Her followers become known as the Created.
The Created conflict drives the game’s central pursuit of Cortana. Roland, the AI aboard the UNSC Infinity, remains loyal to humanity and is not the leader of the uprising.